Benign Neoplasms 2025 PDF

Understanding Oral Pathology the Oral Cavity Lecture Notes for Students 0  Benign Neoplasms Glossary Te...

Understanding Oral Pathology the Oral Cavity Lecture Notes for Students 0  Benign Neoplasms Glossary Term Meaning atrophy decrease in size of an organ or tissue ‫ضمور‬ autonomous Behaving independently; no control on it by external forces ‫مستقل بذاته‬ Resemblance of neoplastic cells to the cell from which they originated differentiation ُ ‫تمي‬ ectopic Normal tissue in an abnormal site ‫ منبوذ‬،‫مقص‬ any tumor like enlargement situated on the gingival or alveolar mucosa. epulis The word only describes the location of the mass not the nature of the lesion. hamartoma Normal tissue in normal site in excessive amount ipsilateral Same side ‫بنفس الجانب‬ tumor implants in distant sites; discontinuous with the primary tumor metastasis ‫نمو ثانوي لورم خبيث‬ New, abnormal growth in which cell multiplication is uncontrolled and neoplasm progressive. ‫ورم‬ nidus a focus around which a lesion develops ‫ منشأ‬،‫مركز‬ small blood clots in a vein that harden over time due to calcification (less phleboliths than 5 millimeters). Also called vein stones. pleomorphism Occurrence in more than one shape ‫تعدد األشكال‬ polarity Structural orientation of cells ‫قطبية الخلية‬ staghorn branched horns on the head of an adult deer ‫قرون الوعل‬ 1  Benign Neoplasms Chapter outline 1. Differences between benign and malignant neoplasms: - Clinical - Histological 2. Benign Neoplasms of Epithelial Origin: i. Squamous cell papilloma ii. Keratoacanthoma 3. Benign Neoplasms of Mesenchymal Origin: A) Fibroblastic and myofibroblastic D) Neural tumors tumors 1. Granular cell tumor 1. Fibroma 2. Neurofibroma 2. Desmoid-type fibromatosis 3. Schwannoma 3. Solitary fibrous tumor E) Maxillofacial bone & cartilage B) Adipocytic tumors: Lipoma tumors: C) Muscle tumors: Myomas 1. Osteoma 2. osteochondroma 3. Desmoplastic fibroma 4. Vascular Anomalies i. Vascular Tumors: a. Hemangioma of infancy b. congenital hemangioma ii. Vascular malformation: a. Capillary malformation b. Venous malformation c. Lymphatic malformation d. Intrabony vascular malformation 5. Melanocytic Nevi i. Acquired melanocytic lesions - Junctional, compound and intradermal - Blue nevus - Spitz nevus - Halo nevus ii. Congenital melanocytic lesions 2  Benign Neoplasms Benign Neoplasms Neoplasm: A neoplasm is a new growth forming an abnormal mass of tissue which is characterized by the following: -It is autonomous i.e. does not follow the normal growth mechanism -It undergoes unlimited proliferation -It does not regress or undergo atrophy with withdrawal of the possible initiating factor. Classification of neoplasms I- According to histogenesis (type of tissue origin): II- According to behavior: 3  Benign Neoplasms Differences between benign and malignant neoplasms: 1- Clinical and gross appearance: Point of Benign neoplasm Malignant neoplasm comparison 1-Growth Slow and gradual rate Rapid rate Expansile Infiltration and invasion 2- Ulceration Unusual, they usually have an Frequent surface ulceration due intact surface unless the mass is to necrosis traumatized 3- Hemorrhage Unusual unless the mass is Frequent hemorrhage due to traumatized weak vasculature 4- Evidence of Never Frequent metastasis metastasis 5- Size Small compared to malignancy Large compared to benign within the same time frame within the same time frame 6- Borders Well-defined mass with smooth Ill-defined mass with irregular pushing edges infiltrating edges 7- Fixation Not fixed to the surrounding Fixed tissues 8- Recurrence Does not recur when properly surgically excised, or often recur are of rare recurrence 4  Benign Neoplasms 2- Histologic features: Point of Benign neoplasms Malignant neoplasms comparison Range from well 1. Differentiation Well differentiated differentiated to undifferentiated. 2. Adhesion & Maintained Lost polarity of cells 3. cellular Cells uniform in size, marked cellular Pleomorphism shape and staining reaction pleomorphism 4. Nuclear No Marked pleomorphism Increased normal and 5. Mitosis Few normal mitosis abnormal mitosis 5  Benign Neoplasms BENIGN NEOPLASMS OF EPITHELIAL ORIGIN Epithelial benign neoplasms from surface from from or lining glandular odontogenic epithelium epithelium epithelium e.g. squamous cell e.g. papilloma and adenomas ameloblastoma keratoacanthoma 1- Squamous cell papilloma Definition It is a benign neoplasm of surface epithelium arising on skin and mucous membrane. Clinically: Site: tongue, palate or lip Signs and symptoms: It appears as an exophytic growth formed of numerous finger- like projections giving the lesion a verrucous surface (cauliflower like appearance). Papilloma may be soft in consistency and pink in color (non-keratinized) or may be firm in consistency and white in color (hyperkeratinized). Grow rapidly to a maximum size of about 0.5cm, with little or no change after. 6  Benign Neoplasms Papilloma may also occur solitary or may be multiple (as in focal dermal hypoplasia syndrome). Histologically: Epithelium Multiple thin long finger-like projections Each is made up of hyperplastic stratified squamous epithelium It could be non-keratinized or covered by a layer of keratin Connective tissue The finger-like epithelial projections are supported by thin branched fibrovascular connective tissue cores. D.D.: Clinically and histologically: papilloma is similar to virus induced verrucae as verruca vulgaris, Heck’s disease and condyloma acuminatum. How can you differentiate squamous cell papilloma from similar lesions? Verruca vulgaris: has a prominent granular cell layer and rete ridges are pointed and converge towards the center of the lesion (cupping effect). Heck’s disease: rete ridges are wide and often club shaped and extend to the same level as the adjacent normal epithelium and epithelium contains mitosoid cells Condyloma acuminatum: rete ridges are broader and blunter than squamous cell papilloma and may occur in association with AIDS 7  Benign Neoplasms 2- Keratoacanthoma (self-healing carcinoma) Definition It is a self-limiting benign epithelial tumor that resembles well differentiated squamous cell carcinoma, clinically and histologically. Etiology and pathogenesis Unknown, however, it may be due to: Genetic or viral factors. Actinic radiation (since the lesion is of frequent occurrence on sun exposed surfaces of the skin). Clinically: Age: old age (50-70 years) Sex: males more than females Site: sun exposed areas of the skin as: skin of cheeks, nose and lip, rare intraorally. Signs and symptoms: It appears as an elevated small firm nodule with a central depression filled with keratin. Most lesions are asymptomatic, although pruritus and mild tenderness are possible. Keratoacanthoma has an unusual clinical course: i. it begins as a small firm nodule of 1-2mm in diameter then develops into its full size 1.5-2 cm. in diameter over a period of 4-8 weeks. ii. It persists as a static lesion for another 4-8 weeks iii. then it undergoes spontaneous regression within the following 6-8 weeks by expulsion of its keratin core and heals with scar tissue. 8  Benign Neoplasms Histologically: Epithelium: i. Hyperplastic stratified squamous epithelium growing into the underlying connective tissue as tongue like projections (pseudoepitheliomatous hyperplasia). ii. The surface is covered by a thick layer of keratin with central plugging. iii. The epithelial cells show abrupt dysplastic features with occasional atypia. Connective tissue: The connective tissue stroma is infiltrated with inflammatory cells. Differential Diagnosis: To differentiate between keratoacanthoma and epidermoid carcinoma, markers are used. The markers used are those which indicate keratinocyte differentiation. Involucrin is a protein linked to terminal keratinocyte differentiation. So, antibodies against the protein involucrin are used Higher levels of involucrin suggest more complete differentiation. - More involucrin indicates keratoacanthoma. - Less involucrin suggests squamous cell carcinoma. Treatment  Surgical removal.  It is advised to be surgically removed because if it is left to heal on its own, scar tissue will be formed. 9  Benign Neoplasms BENIGN NEOPLASMS OF MESENCHYMAL ORIGIN A) Fibroblastic and myofibroblastic tumors 1- Fibroma 2- Desmoid-type fibromatosis 3- Solitary fibrous tumor 1- Fibroma It is a benign neoplasm of fibrous connective tissue. It is the most common tumor of the oral cavity. However, it is doubtful that it represents a true neoplasm, in most instances; it may represent a reactive hyperplasia of fibrous C.T. (irritational fibroma) [excluded in WHO 2022] 2- Desmoid-type fibromatosis It is a locally infiltrative, non-metastasizing, myofibroblastic neoplasm.  Etiology: May be related to trauma, genetic dysregulation or Gardner syndrome.  Signs and symptoms: * No pain at the beginning. * Lesion can become large (> 5 cm) and becomes symptomatic; as it invades the surrounding bone, muscles, nerves and vasculature. 10  Benign Neoplasms  Site: neck, mandible and tongue.  Histopathology:  Infiltrative long fascicles of myofibroblasts  Highly collagenized stroma 3- Solitary Fibrous Tumor It is a fibroblastic tumor characterized by a prominent, branching, thin-walled, dilated (staghorn) vasculature.  Clinically: The lesion is usually a slow-growing, painless and well-circumscribed.  Histopathology: Typically circumscribed neoplasm formed of haphazardly arranged spindle cells (pattern-less patterns). Tumor shows variable cellularity and collagen density. Prominent staghorn vasculature This is what staghorn looks like 11  Benign Neoplasms Solitary Fibrous Tumor Hyper-cellularity Low cellularity 12  Benign Neoplasms B) Adipocytic tumors (Lipomas): It is a benign neoplasm of adipose tissue, which is very rare intraorally.  Clinically: Site: buccal mucosa and buccal vestibule are the most common intraoral sites. Signs and symptoms Slowly growing Sessile or pedunculated Smooth or lobulated painless mass. yellowish in color Soft in consistency  Histologically: i. The lesion is capsulated ii. It is formed of mature fat cells which appear as polyhedral cells with clear cytoplasm, their nuclei are compressed against one side of the cell membrane (signet ring appearance) C) Muscle tumors (myomas): Leiomyomas arise from smooth muscles Myomas Rhabdomyomas arise from striated muscles N.B: Smooth muscle fibers are found intraorally in the wall of blood vessels and in circumvallate papillae of the tongue. 13  Benign Neoplasms 1- Leiomyoma: A benign neoplasm of smooth muscles, which is very rare in oral cavity, and found intraorally related to walls of blood vessels mostly in lip and tongue.  Histopathology: It consists of interlacing short bundles of smooth muscle cells. Their nuclei are blunt- ended nuclei (Cigar- shaped) 2- Rhabdomyoma: A benign neoplasm of skeletal muscles, it occurs predominantly in head & neck It is sub-classified into two major categories: Adult rhabdomyomas (wide age range) Fetal rhabdomyomas (newborns and young children)  Clinical Features: Site: They favor the tongue, floor of mouth and lips Signs and symptoms: Tumors present as soft, painless and non-tender masses.  Histopathology: ▪ Adult type: Composed of variably sized, deeply eosinophilic polygonal cells and cells with vacuolated cytoplasm (spider cells) in connective tissue stroma. Cross striations may be seen. 14  Benign Neoplasms D) Neural tumors: Lesions of neural crest cell origin in oral pathology include lesions which originate from nerve cells or melanocytes. 1- Granular cell tumor 2- Neurofibroma 3- Schwannoma 1- Granular cell tumor It is an uncommon benign soft tissue neoplasm that shows a preference for the oral cavity. Its origin was debatable until studies showed that neural crest cell origin is favored, as it is supported by the presence of S-100 protein (marker for nerve cells). Clinically:  Site: The most common site is the tongue (dorsal surface). The buccal mucosa is the second most common intraoral location.  Signs and symptoms Asymptomatic slowly growing sessile nodule 1-2 cm in diameter Usually a solitary lesion. Histologically: i. It consists of irregularly arranged strands, nests and sheets of large round or polyhedral cells. ii. These cells show granular eosinophilic cytoplasm. iii. The granules are evenly distributed around centrally placed darkly stained nucleus. iv. Nerve bundles may be seen. v. The lesion is covered by hyperplastic stratified squamous epithelium which shows atypical proliferation referred to as pseudoepitheliomatous hyperplasia. 15  Benign Neoplasms Granular cell tumor Histological differential diagnosis: - Congenital epulis of newborn. Congenital epulis of newborn 16  Benign Neoplasms Lesions containing granular cells are: Granular cell tumor (granules are phagolysosomes) Congenital epulis of newborn (granules are phagolysosomes) Rhabdomyoma Oncocytoma (granules are giant mitochondria) Warthin’s tumor (granules are giant mitochondria) Point of Granular cell tumor Congenital epulis of newborn comparison Age Middle age (30 yrs.) At birth Tongue or buccal mucosa Gingiva of the anterior part of Site maxilla Thick hyperplastic stratified Thin stratified squamous Covering squamous epithelium epithelium Epithelium (pseudoepitheliomatous hyperplasia) Origin Neural crest cells Unknown, uncertain histogenesis S-100 protein Positive Negative 17  Benign Neoplasms 2- Neurofibroma It is a benign tumor of nerve tissue origin. It arises from a mixture of Schwann cells and perineural fibroblasts (fibrous connective tissue surrounding the axis cylinder) ( Clinically:  Age: early childhood  Site: intraorally tongue and buccal mucosa  Signs and symptoms Neurofibroma exists in two forms: Solitary Neurofibroma Multiple neurofibromatosis type I 1- Solitary (true neoplasm): sessile or pedunculated, painless smooth surfaced swelling on the skin or intraorally on the palate, buccal mucosa or on the alveolar ridge. 2- Multiple neurofibromatosis {von-Recklinghausen disease of skin or neurofibromatosis type-I (NF1)} * It is a hereditary condition inherited as an autosomal dominant trait. * hamartomatous in origin, not neoplastic, but may turn into malignancy 18  Benign Neoplasms The diagnostic criteria for NF-1 are met if a patient has 2 or more of the following features: (To remember use this word to help you remember CAFE SPOT) C afé au lait macules A xillary or inguinal freckling F ibromas: Two or more neurofibromas E yes: Lisch nodules (translucent brown-pigmented spots on the iris; hamartomatous) S keletal deformity P arents: A first-degree relative (parent, sibling, or offspring) with NF1 O ptic T umor (glioma) Multiple neurofibromas Lisch nodules Café au lait macules Histologically: i. Interlacing bundles of spindle shaped cells with thin wavy nuclei. ii. delicate collagen bundles resembling shredded carrots. iii. Small nerve axons which can be demonstrated within the tumor tissue by using silver stains. iv. Melanocytes may be sometimes found in the tumor. 19  Benign Neoplasms Neurofibromatosis Treatment and Prognosis: The treatment for solitary neurofibromas is local surgical excision, and recurrence is rare. Any patient with a lesion that is diagnosed as neurofibroma should be evaluated clinically for the possibility of neurofibromatosis. Malignant transformation of solitary neurofibromas can occur, although the risk is remote, compared with that in patients with neurofibromatosis. There is no specific therapy for NF1, and treatment often is directed toward prevention or management of complications. Facial neurofibromas can be removed for cosmetic purposes. One of the most feared complications in neurofibromatosis type I is the development of cancer, most often a malignant peripheral nerve sheath tumor (neurofibrosarcoma; malignant schwannoma), which has been reported to occur in about 5% of cases. 20  Benign Neoplasms 3- Neurilemmoma (Schwannoma) The schwannoma is a benign neural neoplasm of Schwann cell origin. Clinically:  Site: The tongue is the most common location. On occasion, the tumor may arise centrally within bone and may produce bony expansion. Intraosseous examples are most common in the posterior mandible.  Signs and symptoms: slow-growing, submucosal encapsulated tumor that typically arises in association with a nerve trunk. Intrabony lesions may produce pain and/or paresthesia. Histopathologic Features: i. The schwannoma is usually an encapsulated Antoni A tumor that demonstrates two microscopic Schwanoma patterns in varying amounts: Antoni B 1) Antoni A and 2) Antoni B. ii. Fascicles of spindle-shaped Schwann cells characterize Antoni A tissue. iii. In Antoni A tissue: the cells form a palisaded arrangement around central acellular, eosinophilic areas known as Verocay bodies. iv. Antoni B tissue is the cells and fibers are loosely and haphazardly arranged within a loose, myxomatous stroma. 21  Benign Neoplasms Treatment: surgical excision Antoni A Antoni B Antoni type A 22  Benign Neoplasms E) Maxillofacial bone & cartilage tumors: 1- Osteoma 2- Osteochondroma 3- Desmoplastic fibroma 1- Osteoma It is a benign neoplasm of bone. It may be solitary or multiple as in case of Gardner’s syndrome (familial adenomatous polyposis). Clinically:  Age: at any age from10-70 yrs.  Signs and symptoms: Slowly growing hard swelling. More common in mandible than maxilla (with the mandibular condyle being a common site). Soft tissue osteoma may appear in the tongue and is termed osteoma mucosae or osseous choristoma. Osseous choristoma Osteoma 23  Benign Neoplasms Radiographically: Well circumscribed radio-opaque mass. Histologically: It consists of dense compact bone (compact osteoma) or cancellous bone (cancellous osteoma). Foci of cartilage may be found. Compact Osteoma Cancellous Osteoma Chondroma is a benign neoplasm of a cartilage tissue. It is wise to consider chondroma of the jaw as a potential chondrosarcoma because the microscopic distinction between benign chondroma and low-grade chondrosarcoma of the jaw is difficult. That’s why, it was omitted by WHO (5th edition) from classification of benign neoplasms. 24  Benign Neoplasms 2- Osteochondroma Osteochondroma is a cartilage-capped bony projection arising on the external surface of bone, continuous with underlying bone. It usually occurs at sites of endochondral ossification, which are limited in the maxillofacial bones. Trauma or radiation therapy in childhood may be the etiological factor. The most common features are asymmetry, malocclusion, pain, and limited mouth opening. hyaline cartilaginous cap the underlying bone 25  Benign Neoplasms 3- Desmoplastic Fibroma It is a rare benign myofibroblastic locally aggressive neoplasm. It is considered a bony counterpart of soft tissue fibromatosis. Clinical Features:  Commonly younger than 30 years of age  More than 80% of head and neck cases affect the mandible.  Limited mouth opening, malocclusion, tooth mobility, tooth displacement and proptosis Radiology Description:  Multilocular radiolucency  Bone is expanded, and the cortex is thinned  Erosion through the cortex and extension into soft tissue may be seen. Histopathological Features:  Mature, plump fibroblasts  Separated by abundant collagen  Thin walled, dilated vascular channels Treatment and Prognosis:  Although the desmoplastic fibroma is a benign tumor, radical excision is the treatment of choice due to: - The tumor is locally aggressive - Extensive bone destruction and soft tissue extension  Long-term prognosis is good, but recurrence may occur so follow up is recommended 26  Benign Neoplasms VASCULAR ANOMALIES VASCULAR ANOMALIES 1. Vascular tumors 2.Vacular malformations irregular vascular development (dys- Proliferation of endothelial cells morphogenesis), while endothelial turnover is stable cannot be recognized at birth; but arise present at birth; most common on subsequently during the first 8 weeks of the face, particularly along the distribution life of the trigeminal nerve. do not have a growth phase, nor an rapid growth phase with endothelial cell involution phase. Vascular malformations proliferation, followed by gradual tend to grow proportionately with the involution child, never regress, and persist throughout life Females : males (ratio of 4 : 1) lesions are named based on the primary Head is the most common location vessel that is malformed Examples: a. Capillary malformation (Port-wine stain) Examples: b. Venous malformation (cavernous a. Hemangioma of infancy hemangioma) b. Congenital hemangioma c. Lymphatic malformation (lymphangioma/ Cystic hygroma) 27  Benign Neoplasms 1- Vascular tumors a- Hemangioma of infancy b- Congenital hemangioma a- Hemangioma of infancy most common type of vascular tumor in babies Etiology: Hypoxic stress is a major trigger characterized by rapid growth in the first few months, followed by spontaneous regression in early childhood. Superficial tumors of the skin appear raised and bosselated with a bright- red color (“strawberry” hemangioma) b- Congenital hemangioma Congenital hemangiomas are present and fully formed at birth. They do not have the postnatal phase of proliferation common to infantile hemangiomas. 2 main variants of congenital hemangioma: non-involuting, and rapidly involuting Histopathologic Features: 1. Increased number of vessels lined by a monolayer of flat endothelial cells. 2. Capillary hemangiomas are formed of tiny sized capillaries; while cavernous hemangiomas are formed of large blood spaces that show papillary infoldings. 3. The vessels contain red blood cells. 28  Benign Neoplasms Hemangioma Hemangioma; well-formed capillary-sized vessels Treatment and Prognosis ▪ Because most hemangiomas of infancy undergo involution, management often consists of follow up. ▪ Parents should be informed that although rapid growth may be seen, regression will occur. ▪ For problematic or life-threatening hemangiomas, pharmacologic therapy is the first line of treatment. 2- Vascular malformation a- Capillary malformation port-wine stain/ Sturge -Weber b- Venous malformation hemangioma c- Lymphatic malformation d- Intrabony vascular malformation 29  Benign Neoplasms a- Capillary malformation (Port-wine stain/ Sturge -Weber syndrome) Port wine stains are pink or purple macular lesions that grow in proportion with the patient’s growth. As the patient gets older, the lesion darkens and becomes nodular because of vascular gradual distention. They are most common on the face, particularly along the distribution of the trigeminal nerve. A syndrome associated with capillary malformations is: Sturge-Weber syndrome. Sturge-Weber syndrome is a rare, non-hereditary developmental condition that is characterized by a hamartomatous vascular proliferation involving the tissues of the brain and face. It is characterized by: port wine stains associated intracranial lesions neurologic manifestations as convulsions due to vascular malformations in the brain. Ocular involvement as glaucoma, exophthalmos and hemangioma of choroids Intraoral involvement in Sturge-Weber syndrome is common, resulting in hypervascular changes to the ipsilateral (same side) mucosa. 30  Benign Neoplasms Histopathologic Features i. Numerous dilated blood vessels filled with red blood cells (capillary- sized). ii. These vessels are rounded in contour and lined by thin, elongated endothelial cells. iii. Port wine stain vessel walls become more thickened and fibrous with time. Dilated blood vessels with rounded contour filled with erythrocytes Clinical considerations: Port wine nevi that affect the gingiva can make flossing and dental prophylaxis difficult. Great care must be taken when performing surgical procedures in affected areas of the mouth because significant hemorrhage may occur. 31  Benign Neoplasms b- Venous malformation present at birth Typically blue due to venous dilatation. Easily compressible They often grow proportionately with the growth of the child Secondary thrombosis and phleboliths formation (tiny, calcified blood clots in a vein) can occur. This accounts for morning pain due to stasis and microthrombi within the veins. Histopathologic Features Excessive numbers of dilated blood vessels filled with red blood cells (cavernous- sized). 32  Benign Neoplasms c- Lymphatic malformation (Lymphangioma/ Cystic hygroma) Lymphatic malformation is a benign hamartomatous growth of the lymphatic system. Etiology: They result from a blockage or defect of the lymphatic vessels during development. Signs and symptoms: - Superficial lesions are manifested clinically as papillary projections of the same color of adjacent mucosa or slightly redder. - The diffuse deep lesions show no change in the surface texture or color of the mucosa involved. In case of tongue, deep diffuse lymphangioma causes macroglossia. A lymphatic malformation formed of multiloculated cyst-like spaces containing lymph is termed (cystic hygroma). Cystic hygromas are benign, but can be disfiguring. Common in the head and neck areas. 33  Benign Neoplasms Histologically: i- Lymphatic malformation consists of lymphatic vessels that may show mild dilatation (microcystic) or macroscopic cyst like structures (macrocystic) ii- The lymphatic spaces are either empty or contain lymphoid material and occasional blood cells. d- Intrabony vascular malformation Intrabony vascular malformation are usually detected during the first three decades of life. They occur three times more often in the mandible than the maxilla. The lesion may be completely asymptomatic, although some cases are associated with pain and swelling. Mobility of teeth or bleeding from the gingival sulcus may occur. Radiographic appearance: Most commonly, multilocular radiolucent defect. The individual loculations may be small (honeycomb appearance) or large (soap bubble appearance). Large malformations may cause cortical expansion, and occasionally a “sunburst” radiographic pattern. 34  Benign Neoplasms A “sunburst” radiographic appearance is radiographic descriptive term given to a n intra-bony lesion when the lesion grows too fast and the periosteum does not have enough time to lay down a new layer and instead the Sharpey's fibers stretch out perpendicular to the bone. It is frequently associated with osteosarcoma but can also occur with other aggressive bony lesions such as an Ewing sarcoma or osteoblastic metastases (see malignant chapter) Clinical considerations: Intrabony vascular malformation of the jaws are potentially dangerous lesions because of the risk of severe bleeding, which may occur spontaneously or during surgical manipulation. Needle aspiration of any undiagnosed intrabony lesion before biopsy is a wise precaution to rule out the possibility of a vascular malformation. Severe and even fatal hemorrhages have occurred after incisional biopsy or extraction of teeth in the area of such lesions. 35  Benign Neoplasms MELANOCYTIC NEVI They are tumor like malformation of skin or mucous membrane formed of cells native to the tissue. Melanocytic nevi are regarded as hamartomatous lesions. Hamartomas are a group of developmental malformations that present as a tumor- like condition, characterized by the presence of normal tissue in normal site, but in an exaggerated manner (excessive amounts). Melanoblasts arise from neural crest cells at the dorsal aspect of the embryo and migrate via the peripheral nerve to settle at the dermo-epidermal junction as clear mature melanocytes. Melanocytes rest in between the basal cells. Melanin pigments are synthesized in melanocytes, then are transferred to the dendritic processes of the melanocytes to protect the nuclei of epithelial cells from the damaging effect of actinic rays. If melanin is extruded outside the cells, macrophages engulf it and are then known as melanophores. 36  Benign Neoplasms I- Acquired melanocytic nevus Acquired melanocytic nevus is the most commonly recognized nevus (common mole). It is a benign localized proliferation of nevus cells derived from the neural crest. It occurs with an average of 10 to 40 cutaneous nevi per white adult. Intraoral lesions are uncommon. They are called intramucosal nevi. Most arise on the palate, mucobuccal fold, or gingiva One in five intraoral nevi lack clinical pigmentation Acquired melanocytic nevi evolve through several developmental stages: junctional, compound, and intradermal. 37  Benign Neoplasms Junctional Nevus Compound Nevus Intradermal Nevus Location of at the dermo- In both the dermo- In the connective epidermal junction melanocytes epidermal junction & the C. T. tissue sharply demarcated, slightly elevated, Papillomatous surface Shape macule, less than 6 soft papule with a & hairs may grow mm in diameter smooth surface Brown or tan (less Less pigmented and brown or black pigmented than the may involute and junctional nevus disappear in adult life Color benign, unencapsulated proliferation of nevus cells organized into small, round aggregates. Nevus cells lack the dendritic processes that melanocytes possess. nevus cells confined to nevus cells are found the junction of the nevus cells are only within the epithelium & C.T. present along the connective tissue. They (junctional activity) junctional area and Histopathology especially at the tips of within the connective are not necessarily seen (most are not pigmented) the rete ridges tissue (dropping effect). cells contain abundant cells contain have less cytoplasm and cytoplasm with abundant cytoplasm less melanin; resemble frequent intracellular with frequent lymphocytes melanin intracellular melanin 38  Benign Neoplasms Variants of Acquired Melanocytic Nevi Spitz nevus (Benign Blue Nevus Halo Nevus Juvenile Melanoma) Mostly hand, feet and face skin of the extremities or Site Oral lesions almost always the face during childhood. skin of the trunk seen on the palate Very rare in oral cavity macular or pigmented papule shape Dome shaped or papule less dome-shaped, smaller than or macule surrounded by a than 6 mm in diameter 1 cm in diameter hypopigmented border, Blue or blue-black lesion. The hypopigmented border Melanin is deep so the light resulting from nevus cell reflected passes through the pink to reddish-brown and melanocyte destruction overlying tissue. (Tyndall by the immune system effect)* Color - nests of nevus cells - collection of elongated, vertically arranged as in slender melanocytes with compound nevus. The dendritic extensions and junctional element numerous melanin granules. Histopathologically, the halo shows junctional activity.** - located deep within the nevus differs from the - Dense eosinophilic Histopathology lamina propria & parallel to routine acquired globules (Kamino bodies) the surface epithelium melanocytic nevi only in the - shares many presence of an intense histopathologic features chronic inflammatory cell with melanoma; however, infiltrate. this lesion has clearly benign biologic behavior Hallo nevus usually - The young age at regresses without treatment presentation and relatively small size help distinguish the Spitz nevus from melanoma 39  Benign Neoplasms II- Congenital melanocytic nevus Clinically: Incidence: - 1% of newborns, mostly on the trunk and extremities - 15% of lesions arise in the head and neck area - Intraoral involvement is rare Size: - small (