Cysts of the Jaws and Oral Cavity PDF

CYSTS OF THE JAWS AND THE ORAL CAVITY BY PROF. MANAL ELNOUAEM Definition: A cyst is a Pathological cavity containing fluid or semi-fluid contents, which has not been created by pus. Majority of these cysts are lined wholly or...

CYSTS OF THE JAWS AND THE ORAL CAVITY BY PROF. MANAL ELNOUAEM Definition: A cyst is a Pathological cavity containing fluid or semi-fluid contents, which has not been created by pus. Majority of these cysts are lined wholly or in partly by epithelium. These cysts are divided into two main groups depending on the suspected origin of the lining epithelium. I-Odontogenic: The epithelial lining is derived from the epithelial residues of the tooth forming organ. They can be subdivided into inflammatory and developmental types depending on their etiology. II -Non odontogenic: The epithelial lining is derived from sources other than the tooth-forming organ. pg. 1  Classification of cysts of the jaws Epithelial cysts: I- Odontogenic cysts A- Inflammatory cysts: 1. (Radicular) Apical cyst. 2. Lateral radicular cyst 3. Residual cyst 4. Paradental cyst. B-Developmental cysts: 1. Dentigerous (Follicular cyst) 2. Eruption cyst. 3. Odontogenic keratocyst. 4. Gingival cyst 5. Lateral Periodontal cyst. 6. Glandular odontogenic cyst. 7. Calcifying odontogenic cyst. (Gorlin) II- Non odontogenic cysts 1. Naso palatine duct (incisive canal) cyst. 2. Naso labial (Naso alveolar) cyst 3. Globulomaxillary cyst. 4. Median cysts III. Non-epithelialized primary bone cyst 1. Solitary bone cyst (Simple, traumatic, haemorrhagic bone cyst). 2. Aneurysmal bone cyst. 3. Stafne’s idiopathic bone cavity. IV-Soft tissue cysts 1. Branchial (Lymphoepithelial cyst). 2. Dermoid cyst. 3. Thyroglossal duct cyst. 4. Salivary gland cysts pg. 2  Odontogenic cysts Definition: The epithelial lining of these cysts originates from residues of the tooth-forming organ 1.The Epithelial Rests of Serres: Persisting after dissolution of the dental lamina,they give rise to; o Odontogenic Keratocyst. o Developmental lateral periodontal cyst o Gingival cyst. 2-The Reduced Enamel Epithelium: Which is derived from the enamel organ and covers the fully-formed crown of the unerupted tooth it gives rise to : o The dentigerous cysts. o Eruption cysts o Inflammatory Paradental cyst. 3-The Rests of Malassez: Formed by fragmentation of the epithelial root sheath of Hertwig. All radicular cysts originate from these residues pg. 3  A-Inflammatory Odontogenic cysts 1- Radicular Apical Cysts Apical radicular cysts are the most common cystic lesions in the jaws apices and are usually associated with the non-vital teeth. Clinical and radiographic features: o Usually small. o Symptomless discovered during routine radiographic examination. o As they enlarge may cause expansion of alveolar bone. o Pain is seldom a feature unless there is acute exacerbation. o Any age, usually rare in deciduous teeth. o May be related to any tooth in the arch 60% in maxillary anterior teeth. In mandible, cysts are usually posterior to the canine. Radiographically: Radicular cysts present as a round or ovoid radiolucency at the root apex. The lesion is often well circumscribed and may be surrounded by a peripheral radiopoque margin continuous with the lamina dura of the involved tooth. Pathogenesis: pg. 4 Epithelial proliferation: Infection from the pulp chamber induces inflammation and proliferation of the epithelial rests of malassez. The mechanism of formation of an epithelial-lined cyst cavity within a granuloma is unclear Two mechanisms have been proposed: 1. Degeneration and death of central cells within a prolifrating mass of epithelium, since the epithelium is a vascular. 2. Degeneration or liquefactive necrosis of granulation tissue,due to encalvement by proliferating strands of epithelium or due to release of toxic products from the infected pulp or from organisms. Cyst expansion and bone resorption: Radicular and many other cysts expand in a balloon like fashion, it expands in all directions. This is governed by the rate of local bone resorption. Bone Resorption: Cyst lining filbroblasts in capsule, release bone resorbing factors which stimulate osteoclastic activity Eg: (prostaglandins). Also (collagenase) which is also synthesized by capsular fibroblasts. Both prostaglandins and collagenase production by fibroblasts are increased by the action of cytokines released by inflammatory cell infiltrate. Eg: Interleukin- 1 released by macrophages. pg. 5 Cyst expansion: Because of large number of osmotically-active molecules in cyst fluid, the contents are hypertonic compared with serum. Cyst wall acts as a Semipermeable membrane , as a result osmotically – active molecules are retained in Cyst lumen. This result in the movement of fluid from the tissues into the lumen, increasing the hydrostatic pressure within the cyst causing it to expand in a unicentric ballooning pattern. Histopathology: Radicular cysts are lined wholly or in part by non- Keratinized stratified squamous epithelium, supported by a fibrous tissue capsule. In newly formed cysts, the epithelial lining is irregular and may vary in thickness i.e. hyperplastic. The fibrous capsule is richly vascular and diffusely infiltrated by inflammatory cells. In established cysts the epithelial lining is more regular in appearance and of fairly uniform thickness and the capsule tends to become more fibrous and less vascular with less inflammatory cells. pg. 6  Breaks in the lining is common. Rushton bodies: Eosinophilic laminated bodies, curved in shape,They may be haematogenous or represent some type of epithelial product. Deposits of cholesterol crystals are common in the capsule of many radicular cysts. In histological sections cholesterol clefts are seen associated with giant cells. Due to discontinuity in the epithelium the cholesterol crystals are found in the cyst lumen Cyst contents: 1. Varies from watery, straw colored fluid to semi-solid brownish material of paste-like consistency. 2. Break down products of degenerating epithelial and inflammatory cells, and connective tissue components. 3. Serum proteins: produced by plasma cells due to inflammation. (immunoglobulin). 4. Water and electrolytes. 5. Cholesterol crystals. 2. Residual Radicular cyst: It is a Radicular cyst which persists after extraction of the causative tooth. They are a common cause of swelling of edentulous jaw in older age. May interfere with the fit of dentures. The lining is of thinner epithelium and shows mild degree inflammation. 3-Lateral inflammatory periodontal cyst: Forms on the side of a non vital tooth as a result of the opening of a lateral branch of the root canal. Must be distinguished from the lateral developmental periodontal cyst. pg. 7  Treatment of inflammatory cysts: 1.Enucleation Is usually very effective. The affected (dead) tooth may be extracted or root filled and preserved. 2.Marsupialization: Is for exceptionally large cysts where fracture is a risk. 4-Paradental cyst: Paradental cysts occasionally result from inflammation around partially erupted teeth, particularly mandibular 3rd molars. Usually between the ages of 20-25 years. The affected tooth is vital, but shows pericoronitis. Histologically the cyst shows the same linning of a radicular cysts but more intense inflammatory infiltrate is seen in the wall. Treatment: Enucleation is effective. N.B. The tooth is vital. Buccal bifurcation cyst: type of paradental cyst that arise in bifurcation areas B-Developmental odontogenic cysts 1) Dentigerous cyst The dentigerous cyst surrounds the crown of an unerupted tooth and is a dilatation of the follicle. The cyst is attached to the neck of the tooth, prevents its eruption and may displace it for a considerable distance. Considered most common type of developmental Odontogenic cyst pg. 8  Clinical features: Age: over a wide range, although many are detected in adolescents and young adults, there is increase prevalence up to the fifth decade. Uncommon in children. Sex: More than twice as common in males as females. Symptoms: Like other cysts, uncomplicated dentigerous cysts cause no symptoms until the swelling becomes noticeable. Usually found in routine-radiographic examination or when looking for the cause of a missing tooth. No pain, unless there is inflammation. Site: the mandibular third molar and then maxillary permanent canines, maxillary third molars and mandibular premolars. i.e. It is associated with teeth which are commonly impacted or erupt late. They may also be associated with supernumerary teeth. X-Ray picture The cavity is well circumscribed, rounded usually unilocular and contains the crown of a tooth, displaced from its normal position. Occasionally there may show pseudo loculation as a result of trabeculation of the bony wall. The slow growth of dentigerous cyst usually results in a sclerotic bony outline and a well-defined cortex. Pathogenesis: The dentigerous cysts arise as a result accumulation of fluid between reduced enamel epithelium and tooth crown. It originates by separation of follicle from the crown of unerupted tooth. The mechanism of expansion of the cyst is probably similar to that of the radicular cysts, and is dependent on bone resorption and hydrostatic pressure. Histopathology of dentigerous cyst: The lining of dentigerous cyst is typically a thin, regular layer, of non-keratinized stratified squamous epithelium (some times flattened or low cuboidal). Very rarely keratinized Mucous cells are present in the epithelial lining. Multiple discontinuities are observed. pg. 9  The lining is supported by a fibrous connective tissue capsule free from inflammatory cell infiltration, unless there has been secondary infection. Islands of odontogenic epithelium may be seen. Macroscopic features: 1.Central type: Most common type, the cysts completely surrounds the crown of the tooth. 2.Lateral type: The cyst projects laterally from the side of the tooth 3.Circumferential type: Cystic change occurs in a band around the circumference of the amelocemental junction producing a dough-nut-shaped lesion. Management and treatment: ▪ If the tooth is in a favourable position and space is available, it may occasionally be possible to marsupilize a dentigerous cyst to allow the tooth to erupt. ▪ Extraction of the associated tooth and careful enucleation of the soft tissue component is the therapy in most instances. Complications of the untreated dentigerous cyst: 1. Transformation of the epithelial lining of the dentigerous cyst into an ameloblastma is a familiar occurrence. pg. 10  2. Rarely, dysplastic or carcinomatous transformation of the lining epithelium. 3. Finally,in cases,inwhich mucous cells are present, development intraosseous mucoepidermoid carcinoma. Differential diagnosis: Of a pericoronal radiolucency, In addition to dentigerous cyst: 1. Unicystic ameloblastoma. 2. An odontogenic keratocyst in relation to a tooth. 3. Ameloblastic fibroma (in post-mandibular region or in maxilla in young age). 4. AOT (if in maxillary canine) 2. Eruption cyst: An eruption cyst occasionally forms over a tooth about to erupt. It is a soft tissue cyst. It arises from enamel organ epithelium after enamel formation is complete. It is a superficial dentigerous cyst. Clinical picture: Age: Children are usually affected. Site: The cyst lies superficially in the gingival overlying the unerupted tooth (eruption hematoma). It appears as a soft, rounded, bluish swelling Histology: The lining of the eruption cyst may be similar to the dentigerous cyst, the fibrous capsule shows inflammatory cells possibly as a result of trauma. The epithelial lining is separated from the alveolar mucosa by a thin layer of fibrous tissue. Cyst contents: May contain blood in addition to the yellowish protein fluid, as a result of trauma. pg. 11 Management: The cyst roof may be removed to allow the tooth to erupt, most of them burst spontaneously. Important considerations: Dentigerous and radicular cysts continue to enlarge as a result of increased osmotic pressure in the lumen of the cyst. Where as keratocysts growth was related to unknown factors (either inherited in epithelium its self or enzymatic activity as fibrous wall) Keratocysts are regarded as benign cystic neoplasms rather than cysts. 3-Odontogenic keratocyst The odontogenic keratocyst is a relatively uncommon lesion which has aroused much interest because of its unusual growth pattern and tendency to recur. It arises from remnants of the dental lamina. Several investigations have suggested that odontogenic keratocysts has been regarded as benign cyst neoplasms rather than cysts. And in latest WHO classification of odontogenic tumors, these have been given name keratocystic odontogenic tumor. (parakeratinzing odontogenic cysts) Clinical features: Age:2nd and 3rd decades and sometimes in 5th decade. Sex: Males are more affected. Site:70% to 80% in mandible. Posterior mandibular region (50%) of all cases, posterior body and ascending ramus. In maxilla if affected usually posterior to first premolar. Symptoms: No or few symptoms, unless inflamed. Grow in an antroposterior direction, and can reach large size without expansion. X-Ray Picture: Highly suggestive but not diagnostic Well-defined radiolucencies, with smooth margins and thin radio- opaque margins. It may be unilocular or multilocular. pg. 12  Many present in apparent dentigerous relation-ship associated with unerupted third molars, but the crowns are usually separated from the cyst cavity. The roots of adjacent teeth may become displaced. 25% to 40% are related to unerupted tooth. Histopathology Cyst wall usually thin, folded and lined by a regular continuous layer of stratified squamous epithelium, 5-10 layers. The basal layer is well defined and consists of palisaded columnar or occasionally cuboidal cells. The suprabasal cells resemble those of the stratum spinosum of the oral epithelium. Parakeratosis predominantes, but areas of orthokeratinization are seen. It give a heavy corrugated appearance. Mitotic activity is higher than in other cysts. The fibrous C.T. capsule usually thin and generally free from inflammatory cell infiltration. Small groups of epithelial cells are found in the capsule. Satellite cysts ,cords, or islands of od epithelium are seen pg. 13  N.B Retention of these satellite cysts after enucleation of the main cyst is one of the factors responsible for the high recurrence rate. Odontogenic keratocyst must not be used to describe any odontogenic cyst producing keratin. Pathogenesis and expansion Derived from remnants of dental lamina, stimulus of cystic transformation is unknown. Although hydrostatic forces are involved in expansion, other possible factors are also responsible. 1-Hydrostatic forces: due to hypertonic contents of the cyst as in radicular cyst 2-Active epithelial growth: Epithelial lining exhibit greater mitotic activity. (Proliferation of local groups may account for the folding in the cyst lining and projections of the cyst in the cancellous spaces). 3-Production of bone resorbing factors: The odontogenic keratocyst releases bone resorbing factors including. Prostaglandins Collagenase Interleukin-1 and 6. They are less than in radicular cysts, and so they extend through the less dense cancellous bone. 4- Accumilation of Mural squames. Management: 1.Diagnosis should be confirmed before operation. 2.Treatment should be complete enucleation. (recurrence rate up to 60%). 3. (Carnoy’s fluid improves the result ) chemical cauterization of bony cavity after cyst removal, also used intra luminaly to free the cyst from the bony wall to allow easier removal. 4.Polyethelyne drainage tube to allow decompression and subsequent reduction in size of cystic cavity. Decompression treatment results in thickening of the lining , thus allowing easier removal with apparently lower recurrence rate. 5.Resection provides the lowest recurrence. pg. 14  Orthokeratinizng odontogenic cysts: The designtion orthokeratinized odontogenic cyst does not denote a specific clinical type of odontogenic cyst but refers only to an odontogenic cyst that microscopically has an orthokeratinized epithelial lining. Although such lesions were originally called the orthokeratinized variant of odontogenic keratocyst, it is generally accepted that they are clinicopathologically different from the more common parakeratinized odontogenic keratocyst and should be placed into a different category. Orthokeratinized odontogenic cysts represent 7% to 17% of all keratinizing jaw cysts. Clinical and Histopathological features Predominantly in young adults Male to female 2: 1 Mandible twice as maxilla As unilocular radiolucency more common than multilocular ones Epithelial lining is relatively thin The cyst doesn’t demonstrate hyperchromatic palisaded basal cell layer. (which is an important characteristic feature of true odontogenic keratocysts) Keratohyaline granules may be prominent near the orthokeratinization. pg. 15 THE BASAL CELL NEAVUS SYNDROME [GORLIN AND GOLTZ- SYNDROME] (Inherited as an autosomal dominant trait) Multiple odontogenic keratocyst. Epidermal cysts of the skin. Multiple naevoid basal cell carcinomas of the skin. Skeletal abnormalities (Bifid ribs). Enlarged head circumference. Mandibular prognathism and facial dysmorphogenesis may be seen as broad nasal bridge. Calcification in cerebral meninges. [Falx cerebri].due to abnormalities of calcium and phosphate metabolism. (intra cranial calcification) Mild hypertelorism Palmer and planter pits Ovarian fibromas 4-Lateral periodontal cyst It is an uncommon lesion that must be distinguished from lateral radicular cyst associated with a non vital tooth, and from an odontogenic keratocyst arising along the root of a tooth. Clinically: In canine, premolar region. In mandible more than maxilla Middle age patients. May cause expansion. Cause no symptoms unless they erode through the bone and extend in the gingiva. (may appear as a gingival cyst). X-ray Not diagnostic. Discovered on routine x-ray. A well-defined radiolucent area with sclerotic margin, located laterally to the roots of vital teeth. Pathogenesis: It is uncertain. pg. 16  It was suggested that it could arise initially as a lateral dentigerous cyst which is retained in the bone when the tooth erupts. Treatment Conservative enucleation. The cyst should be enucleated and the related tooth can be retained if healthy. [Botryoid odontogenic cyst] A variant and even more rare than the lateral periodontal cyst. It affects the mandibular premolar to canine region. Adults over 50 years.: It is typically multilocular with fine septa of fibrous tissue. Microscopically :Lining consists of flattened non Keratinised epithelium Treatment: It should be enucleated or conservatively excised as it has strong tendency to recur. Botryoid, because of their resemblance to a bunch of grapes 5-Palatal cysts of new born These cysts are of little significance They are due to proliferation of epithelial rest of serres. They are common in neonates, referred to as “Bohn’s Nodules” or “Epstein’s pearls”. Fairly common lesions. Found on the maxillary alveolus, midline of the palate (Epistein’s Pearls) {inclusion cysts} and on the hard and soft palate (Bohn’sNodules) {Minor Salivary glands derived } hence their distribution. Small usually multiple whitish papules. Lining is formed of thin flattened epithelial lining of Parakeratotic surface. Most resolve spontaneously by 3 months of age Gingival cyst of adult o Very rare o Soft tissue counterpart of the lateral periodontal cyst. ▪ After age of 40 Occur in the mandibular canine premolar area. ▪ Located on the facial gingiva of the alveolar mucosa. ▪ Often bluish or bluish gray In colour. ▪ May cause cupping-out of the alveolar bone. pg. 17 o Forms a painless dome like swelling less than 1 cm in diameter. o Lined by thin, flat stratified squamous epithelium with focal plaque and clear cells. o Excision, unlikely recur. 6. Calcifying odontogenic cyst ( Gorlin cyst) Classified into: Dentinogenic ghost cell tumor (epithelial odontogenic ghost cell tumor) with no cystic features. (may be infiltrative or even malignant) regarded as neoplasm. Calcifying odontogenic cyst. (non neoplastic cyst) Gorlin cyst is an uncommon type of cysts, usually grouped with other odontogenic tumours as Odontomes AOT Ameloblastoma This cyst with all its variants is classified by the WHO as an odontogenic tumor rather than cyst. Its cystic nature and innocent clinical behavior in majority of lesions doesn’t go with the change in terminology. Clinically: Age: Usually below the age of 40. Site: 75% of the cases are intra-osseous. Anterior to the first molar tooth. Both jaws are affected. Symptoms: Slowly growing but symptomless. X-Ray: Picture Appears as a well-defined unilocular or multilocular radiolucent area, containing varying amounts of radioopacities. Calcified deposits are also seen. May be associated with the crown of an unerupted tooth. Histologically pg. 18  o The cyst is lined by squamous epithelium with cuboidal or ameloblast-like basal cells. o The overlying layers are more loosely arranged cells resemble stellate reticulum. o The diagnostic feature is (ghost cells). [Swollen, eospinophilic cells , keratinized epithelial cells.] o They may later calcify. o Breakdown of the epithelium may release keratinous debris in the C.T. resulting in foreign body giant-cell reaction. Treatment Behavior is similar to that of non-neoplastic cysts ,and enucleation is effective. Carcinomas arising in odontogenic cysts Most common cysts undergoing malignant changes: Residual periapical cyst Periapical cysts Dentigerous cyst Orthokeratinized odontogenic cyst rather than odontogenic keratocysts Rarely in lateral periodontal cyst II. Non-Odontogenic cysts pg. 19  1-Nasopalatine canal cyst: Commenest of the non-odontogenic cysts. Also known as incisive canal cyst, or may be seen in the palatal soft tissue and so known as cyst of the palatine papilla. Etiology: It arises from the remnants of the nasopalatine duct which connects the oral and nasal cavities in the embryo. (It is present in the midline of the maxilla). Trauma, infection may be the cause that stimulates epithelial proliferation or mucous accumulation due to the presence of goblet cells in the lining. Clinical picture : o 5th or 6th decades. o Males are more affected than females. o Asymptomatic unless infected, and discovered on routine examination. o Or may present as a slowly growing swelling in the anterior region of the palate. o Occasionally may discharge into the mouth through a sinus, with a salty taste. o May be seen in the soft tissue and often known as cyst of the palatine papilla. X-ray picture: A well-defined round or ovoid or heart shaped radiolucency. Sclerotic rim. Usually symmetrical about the mid line, but some may be displaced to one side. Anterior nasal spine is usually centrally superimposed on the lucent defect giving the heart shape. N.B. Must be distinguished from the incisive fossa, usually of 6 or 7 mm) Histopathology There is a wide variation in the epithelial lining features. pg. 20  Stratified squamous epithelium, pseudostratified ciliated columnar epithelium often containing mucous cells, cuboidal epithelium or any combination. [According to relation to nasal or oral cavity] The epithelium is supported by C.T, usually includes prominent neurovascular bundles Collections of mucous glands and chronic inflammatory cell infiltrate may be present. Differential diagnosis: Periapical granuloma. Odontogenic cyst of radicular type. Treatment: Enucleation if the size of the cyst is small marsupialization if the cyst is of large size. 2-Nasolabial cyst It a rare lesion which arises in the soft tissue of the upper lip just below the ala of the nose. Etiology: Was thought to be fissural arising from the remnants of the epith. at site of fusion between the maxillary medial nasal and lateral nasal processes. Or more accepted theory, from the misplaced epithelium of the nasolacrimal duct because of their similar location and histology. Clinical features: It grows slowly obliterating the nasolabial fold and distorting the nostrils. May be bilateral. 4th decade. Females more than males. Histological features: The cysts are usually lined by pseudostratified columnar epith., but stratified squamous epith., mucous cells and ciliated cells may be present. D.D: Radicular inflammatory cysts (clinically) pg. 21  3-Globulomaxillary cyst Very rare lesion occurring between the roots of the maxillary permanent lateral incisor and canine teeth. Clinically: It presents as an inverted unilocular pear-shaped radiolucency. It is accepted that the majority are odontogenic in origin and represent either a developmental lateral periodontal cyst or even a radicular cyst. Etiology: It was thought to develop from epithelial remnant remaining following the joining of the globular portion of medial nasal process with the maxillary process. However these are primarily united together and fusion does not occur therefore epithelial entrapment does not take place. Hence the previous assumption is probable. 4- Median cysts Median palatine cysts Very rare. It was thought to be from epithelium entrapped along line of fusion of lateral palatal shelves of maxilla. The median cyst of the palate probably represents a displaced nasopalatine duct cyst (posteriorly positioned). Median Mandibular Cysts They were thought to be fissural due to epithelial rests entrapped during the fusion of the halves of the mandible during emberyonic life. However the mandible develops as a single bilobed proliferation of mesenchyme with a central isthmus in midline. The isthmus is eleminated as the mandible develops. Therefore no fusion of epithelial lined processes occurs. Therefore those of mandible are likely to be odontogenic in origin III. Non Epithelialized Primary Bone cysts pg. 22  1-Solitary bone cyst Also may be termed: (Simple bone cyst, traumatic bone cyst and haemorrhagic bone cyst) Clinical picture Usually seen in children and adolescents i.e. peak age 2nd decade. No definite sex predilection. Site: Premolar and molar regions of the mandible. Asymptomatic and usually found accidently in X-rays. Only 25% of cases may show expansion of bone. Pathogenesis: Is unknown. It is believed that there is a relation to trauma. Or may be related to heamodynamic disturbance in medullary bone. X-ray picture: Radiolucency of variable size and irregular outline. Scalloping around and between the roots of standing teeth. The margins of the lesion are usually well defined. Histopathology: Surgical exploration to confirm diagnosis reveals a rough bony-walled cavity with no soft tissue lining i.e. empty. In other cases little clear or blood-stained fluid. Histopathologic examination of currettings shows: Delicate layer of loose, vascular C.T. Haemosidrin pigments No epithelial lining. pg. 23  2-Aneurysmal bone cysts Rare in the jaws. Etiology 1) Unknown. 2) Many are preceded by some other primary lesion of bone such as Fibrous dysplasia, giant-cell granuloma. 3) Due to vascular malformation. Clinical picture : Most cases reported in the mandible are in the posterior Part and angle of mandible. It occurs in children and young adults. It presents as a firm painless swelling. X-ray: Unilocular or multilocular radiolucency with ballooned-out appearance due to gross cortical expansion. Microscopic picture: Numerous non endothelial lined blood spaces of varying size containing unclotted blood seperated by cellular fibrous tissue and multinucleated giant cells ,old and recent haemorrhage. Trabeculea of osteoid and woven bone. pg. 24  3-Stafne’s Idiopathic bone cavity Static bone defect /latent bone cyst Uncommon developmental anomaly of the mandible. Symptomless, found by chance. It is a defect and contains ectopic salivary tissue in continuity with the submandibular salivary gland. Diagnosis: By Sialography X-ray: Appears as a round or oval well demarcated radiolucency between the premolar region and angle of the mandible. Usually beneath the inferior dental canal. Usually bilateral. Saucer-shaped depression on the lingual aspect of the mandible. pg. 25  IV. Soft tissue cysts 1-Branchial cyst [Lymphoepithelial cyst] Very rare. They occur deep to or along the anterior border of the sternomastoid muscle at the level of the angle of the mandible. In the oral cavity it is unusual and if present it is seen in the floor of the mouth. Etiology: 1. Arises from cystic degeneration of the epithelial remnants, (found between the branchial clefts, arches and pouches ). 2. Or due to entrapment of epithelium within cervical lymph nodes, followed by cystic degeneration. (This epithelium is thought to be salivary in origin). Clinical picture: o It is seen in late childhood or adulthood. o May be infected, with abcess formation and draining sinus. Microscopic picture: o Usually lined by stratified squamous epithelium or pseudostratified columnar epithelium. o The underlying C.T. shows lymphoid aggregates usually demonstrating well formed germinal centers. 2. Dermoid cyst Uncommon lesion. It is a cyst which develops between the hyoid bone and the mandible. It arises in the midline in the floor of the mouth intraorally or as submental swelling or double chin app. If below geniohyoid muscle].If above it a sublingual swelling may displace the tongue. Etiology: From enclavement of epithelium in the mid line due to incomplete fusion of the mandibular and hyoid branchial arches. pg. 26 Clinical picture Painless, slowly growing. The cyst is soft and fluctuant. Pale yellowish-pink color is noted beneath the thinned intact epithelium. If large it interferes with speech and eating. Microscopically: It is lined by orthokeratinized stratified squamous epithelium. Supported by a fibrous C.T. wall. Sebaceous glands and ectodermal derivatives may be seen. Cyst content: 1. The lumen contains keratinous debris. 2. Sebum is also seen in the cyst cavity. (when sebaceous glands are seen). Treatment: cyst should be dissected out. 3. Thyroglassal tract cyst. It is the most common developmental cyst of the neck. It arises from the residues of the embryonic thyroglassal duct. (from foramen caecum to the location of gland). Most cysts arise in the region of the hyoid bone, or may be seen in the posterior portion of the tongue [Lingual thyroid]. Asymptomatic Microscopic picture: Microscopic findings vary depending upon the location of the cyst. Above level of hyoid bone →stratified squamous epithelium. Below level of hyoid bone → ciliated or columnar epithelium. Thyroid tissue may be seen within the C.T. wall. Treatment : Is complete surgical excision. Before excision of ectopic lingual thyroid it is important to make sure that the patient has functioning thyroid tissue in the neck. N.B. Malignant transformation may occur within the thyroglossal tract cyst giving a papillary adenocarcinoma. pg. 27  4- Salivary Gland Cysts Salivary Mucoceles: A) Mucous extravasation cyst. B) Mucous retention cyst. A) Mucous extravasation cyst Is the most common type of cyst in minor glands. It is not a true cyst as it has no epithelial lining. Usually affects the lower lip, buccal mucosa, floor of the mouth and may be seen in the ventral surface of the tongue [Blandin Nuhn]. Any age, but usually in the second decade. It is usually superficial and rarely larger than 1 cm. in diameter. It appears as a bluish submucosal swelling. There may be history of rupture, collapse and refilling. Pathogenesis Mechanical trauma to the minor salivary gland excretory duct resulting in transaction. Spillage or extravasation of mucous in the surrounding C.T. This mucous induces a secondary inflammatory reaction in the C.T. Neutrophils, macrophages flooding into the area. Granulation tissue response, resulting in the formation of a wall around the mucin pool. Histopathology: Well circumscribed cavity containing mucin surrounded by a thin wall of compressed granulation tissue. The wall is infiltrated by large number of neutrophils, macrophages, lymphocytes and plasma cells. Macrophages may be seen in the lumen. The surrounding salivary tissue demonstrate changes as ductal dilatation and acinic degeneration. D.D: 1) salivary neoplasms 2) vascular malformations 3)lipomas 4)gingival and eruption cyst (if mucocele appears In alveolar mucosa) Treatment: should be excised with underlying gland to prevent recurrence. pg. 28  Mucous retention cyst They are derived from cystic dilatation of a duct and so they are lined by ductal epithelium. [True cyst]. The ducts usually becomes obstructed, and so mucin does not escape. Less common than the extravasation type. Appears over 50 years of age. It is seen in the floor of the mouth, palate, cheek and may be seen in the maxillary sinus. Asymptomatic swelling with size 3 to 10 mm. Mobile, Non-tender and shows no inflammation. Histopathology: Cystic cavity surrounded by ductal epith. Which is usually a double layer of columnar or cuboidal cells. Mucin is found in side the cavity. Surrounding C.T. lacks inflammation. D.D. Salivary Neoplasms. Extravasation mucocele. C.T. Neoplasms. Treatment: Complete removal of the mucous retention cyst and associated lobules of minor salivary glands. pg. 29 Ranula: Uncommon type of salivary cyst arising from the sublingual or submandibular salivary glands The term is best used to describe mucus escape reactions. Source of mucin spillage is usually sublingual gland;to a lesser extent from submandibular gland duct or possibly from minor salivary glands in floor of mouth. May be unilateral and 2-3 cm in diameter. Or may extend across the whole of the floor of the mouth. They are soft, bluish and fluctuant. Painless but may interfere with and mastication and speech. D.D: 1) Dermoid cyst. “Doughy” in consistency and more towards the midline. 2) Salivary gland tumors. 3) Bengin mesenchymal tumours. Treatment Surgical removal is the preferred therapy. Excision of the involved gland is usually performed as well. pg. 30