Integument: Benign Neoplasms PDF

Integument: Benign Neoplasms Layers of the Skin Skin has 3 layers: o Epidermis § Provides a waterproof barrier § Melanocytes in the lower level (determine skin color) o Dermis § Beneath epidermis § Connective tissue, hair follicles, and sweat glands o Hypodermis § Subcutaneous fat § Fat and connecti...

Integument: Benign Neoplasms Layers of the Skin Skin has 3 layers: o Epidermis § Provides a waterproof barrier § Melanocytes in the lower level (determine skin color) o Dermis § Beneath epidermis § Connective tissue, hair follicles, and sweat glands o Hypodermis § Subcutaneous fat § Fat and connective tissue Beneath Epithelial Neoplasms: Seborrheic Keratosis Most common benign epithelial tumor Hyperkeratotic lesions of the epidermis o Variable in color, from tan to brown to black o Well-circumscribed border w rough surface o 2 mm to 3 cm, but can be larger o Appear “stuck on” the surface of the skin Dermatosis Papulosa Nigra Multiple small, brown/black papules Face of dark-skinned ppl Leser-Trelat Sign Pathology: o Acanthosis: Benign overgrowth of stratum spinosum w/o cytologic atypia o "Horn pseudocysts" o “String sign”: uniform depth, can draw a horizontal line parallel to the epidermal surface under the lesion Acrochordon (Skin Tag) Common, small, benign neoplasms In skin folds (e.g., neck, axillae, groin) Recurrence is common Assc w metabolic syndrome No malignant threat in adults Pediatric skin tags may be nevoid basal cell carcinoma à more dangerous Histology: o Composed of a fibrovascular central core covered by squamous epithelium § Small lesion have epidermis that has hyperplasia § Large lesions have epidermis that is flattened o Central core of loose collagen w increased blood vessels +/- local inflammation o Central core in large lesion, have a central core of adipose tissue Epidermal Cyst Most common cutaneous cyst Discrete nodules - implantation and proliferation of epidermal elements within the dermis Multiple epidermal cysts = Gardner syndrome o Variant of familial adenomatous polyposis (FAP) with benign osteomas and intestinal fibromatoses o Screen for colon cancer when cysts are unusual in number or location (e.g., fingers, toes) Clinical features: central punctum – communicates with epidermis and plugged with keratin debris Microscopic features: o Cyst lining = stratified squamous epithelium w a granular layer o Cyst wall does NOT contain eccrine glands, sebaceous glands, hair follicles o Cyst composed of abundant keratin flakes Treatment is unnecessary unless desired Sebaceous Tumors Benign skin adnexal lesions Multiple sebaceous lesions occur as part of Muir– Torre syndrome o Autosomal-dominant disorder, due to mutation in MSH2 mismatch repair gene Microscopic Features (on H&S stain): Vacuolated, bubbly, mature sebocytes, similar to normal sebaceous glands Sebaceous Adenoma Benign tumor of sebaceous glands Some occurrences of multiple SA’s are associated with Muir-Torre syndrome Histologically: o Dark and light areas corresponding to basal cells (dark) and sebaceous cells (light) with cytoplasmic lipid vacuoles o Central sebocytes are white/mature o Peripheral sebocytes are less mature Muir-Torre syndrome: Variant of hereditary nonpolyposis colorectal cancer syndrome (also referred to as Lynch syndrome) Unlike Lynch syndrome, MSH2 is the most common gene mutation in MTS Sweat Gland Tumors Ductal or Glandular differentiation o Eccrine lesions are most common o Apocrine lesions are rare (Eccrine) Poroma Benign sessile nodule, sometimes red and scaly Histologically, 3 types: (1) Poroma: involving both epidermis and dermis (2) Hidroacanthoma simplex: within the epidermis (3) Dermal duct tumor: limited to the dermis Elongated rete ridges or tongues of tumor that push from epidermis into underlying dermis Cylindroma Benign neoplasms Sporadic: present as a solitary lesion Hereditary: numerous cylindromas covering scalp described as “turban tumor” o A variant of Brooke-Spiegler syndrome o Mutation in the cylindromatosis tumor suppressor gene (CYLD) gene Histology: o Arranged in a characteristic “jigsaw puzzle” pattern o 2 types of cells: § (1) large cells with pale-staining nuclei at the central zone § (2) small, basaloid cells at periphery with dark-staining nuclei o Abundant basement membrane deposition o Spherical pink droplets within nests Syringoma Small dermal collection of epithelial tubules, some with a “tadpole” shape, in a dense sclerotic background Tubules lined by single or double layers of bland, monomorphous, cuboidal epithelial cells The double layer of cells surrounding the lumen should be a strong clue of sweat gland differentiation Hair Follicle Tumors Parts of the hair follicle unit: o Infundibulum (deep) § From the epidermal surface to the opening of the sebaceous duct o Isthmus § From the opening of the sebaceous duct to the insertion of the arrector pili muscle o Inferior follicle § From the insertion of the arrector pili muscle to the hair bulb o Germinative matrix § Cluster of proliferative round blue cells that make up the hair bulb - give rise to the hair shaft itself o Hair papilla (superficial) § aka dermal or mesenchymal papilla § Connective tissue and a capillary loop, minimal cell division Trichoepithelioma Form rudimentary hair follicles that do not form actual hair shafts Small flesh colored papules o Sporadic cases are solitary o Familial cases are associated with an autosomal dominant multiple familial trichoepithelioma (MFT) § The gene links to the short arm of chromosome 9 - tumor suppressor genes located here § Mutations in the CYLD gene Histology: o Small horn cysts filled with keratin are present o Dense pink fibrous stroma o Papillary mesenchymal bodies Trichilemmoma Follicular proliferations present as papules on the nose, eyelid, or elsewhere on the face of an adult Often has a verrucous (wart-like) appearance Multiple facial trichilemmomas -> associated with Cowden syndrome (multiple hamartoma syndrome) o Germline mutation of PTEN gene Histology: o Epidermis show verruca-like changes: § Papillomatosis § Hypergranulosis § Foci of parakeratosis § Dilated vessels in the underlying rete o Lobules or plates of uniform epithelial cells with glycogenated clear cytoplasm o Peripheral cells surrounded by thick, hyaline, basement membrane material Morphologically homologous to the outer root sheath of the lower portion of the normal hair follicle Hamartoma A benign growth made up of an abnormal mixture of cells and tissues that are normally found in the area of the body where the growth occur Cutaneous Spindle Cell Neoplasms Benign lesions are more common than malignant tumors include: o Neurilemomas (Schwannomas) o Neurofibromas Most common primary cutaneous sarcomas: o DFSP-Dermatofibrosarcoma protuberans o Leiomyosarcoma o PDS- Pleomorphic dermal sarcoma (PDS) Schwannoma (Neurilemmoma) Benign peripheral nerve sheath tumor Composed of Schwann cells More cellular areas (Antoni A): a haphazard arrangement of cells Loose less cellular areas (Antoni B): loose edematous and mucinous stroma Characteristic Verocay bodies may be seen Neurofibroma Benign nerve-sheath tumor in the peripheral nervous system 90% solitary – multiple lesions found in neurofibromatosis type I (NF1) Inactivation of NF1 (neurofibromin gene) Neurofibromin regulates RAS cell growth signaling pathway Subtypes of neurofibromas: o Plexiform o Diffuse cutaneous o Superficial cutaneous Histology: o Proliferation of all elements of peripheral nerves (rather than just Schwann cells as in Schwannoma) o Cells have wavy serpentine nuclei and pointed ends Neurofibromatosis I Characterized by multiple café au lait spots, multiple cutaneous neurofibromas, Lisch nodules ~50% of NF1 have plexiform neurofibromas Heterozygous NF1 are responsible for neurofibromatosis 1 Neurofibromatosis II Bilateral vestibular schwannomas May develop schwannomas of other cranial and peripheral nerves (meningiomas, ependymomas, and, very rarely, astrocytomas) Autosomal dominant mutation in NF2 gene (schwannomin, merlin, neurofibromin 2) Fibrous Histiocytoma (Dermatofibroma) Proliferation of fibroblasts Usually asymptomatic, although pruritus and tenderness can be present Diagnosis supported by Fitzpatrick's sign (dimpling or retraction of the lesion beneath the skin with lateral compression) Multiple eruptive variant occurs in only 0.3% of patients, usually immunocompromised (HIV or SLE-related) Histology: o Ill-defined dermal lesions o Hyperplasia of overlying epidermis o “Storiform (pinwheel)” pattern of nuclei o Variable numbers of inflammatory cells, foamy macrophages, Touton giant cells, and siderophages o Entrapped thickened, hyaline collagen bundles may be seen at the periphery of the lesion. Rarely metastasize to lung, lymph node, or soft tissue