Skin Disorders - Common Skin Malignancies

Question 1

Basal Cell Carcinoma

Answer 1

•non-melanoma skin cancer (NMSC)
Arise from keratinocytes
Very common
Most commonly from sun exposure
Risk greater in fair skinned individuals
•most common
•UVB exposure
•70% appear on face
•flesh colored papule with translucent or pearly appearance, often with telangiectasia, requenlty with central ulceration
•locally invasive and destructive
•Histology:densely packed basaloid cells with peripheral palisade good, associated with inactivating mutations in the tumor suppressor gene patched 1 (PTCH1), a cell surface receptor in the sonic hedgehog pathway
•Principles of Therapy: excision including MOHs excision if in cosmetically sensitive area, electro-desiccation and curettage; cryosurgery

Question 2

Squamous Cell Carcinoma

Answer 2

•non-melanoma skin cancer (NMSC)
Arise from keratinocytes
Very common
Most commonly from sun exposure
Risk greater in fair skinned individuals
•second most common
•actinic keratosis progresses to SCC in 5% of cases, keratoacanthoma may be a variant
•UVB exposure, immunosuppressants, scars, areas of chronic inflammation, arsenic exposure
•fewer than 5% metastasise to lymph nodes
•variable presentation: in situ erythematous scaly plaque, invading may become nodular and show ulceration
•biopsy for diagnosis
•Histology: in situ -nuclear atypia through all layers of epidermis, invasive - cells with variable cytoplasm, intercellular bridges, nuclear atypia, mitotic figures, keratin pearl formation. Poorly differentiated tumors show increased atypical mitotic figures, higher N/C ratio, less or no keratin pearl formation
•associated with mutations in p53 and/or mutations that increase RAS oncogene signaling and decrease Notch signaling
•Principles of Therapy: excision, electro-desiccation and curettage or cryosurgery. Topical chemotherapy and radiation are also options.

Question 3

Keratoacanthoma

Answer 3

•non-melanoma skin cancer (NMSC)
Arise from keratinocytes
Very common
Most commonly from sun exposure
Risk greater in fair skinned individuals
•rapidly growing, symmetric, cup shaped lesion with central depression filled with keratin debris
•often regresses spontaneously, rarely metastasises
•resembles SCC histologically but can be benign

Question 4

Melanoma

Answer 4

•tumor of melanocytes
•least common of the Big Three, but with greatest metastatic potential
•intense sun exposure during childhood and adolescence, familial component, association with benign nevi esp. atypical nevi
•ABCDE
•tumors show initial radial growth phase, spreading horizontally in epidermis and superficial dermis, then later vertical phase invading deeper dermis and with high risk of metastasis
•Histological: larger than normal melanocytes with large nuclei with chromatin clumped at periphery and eosinophilic nucleoli. Epidermal melanocytes may appear in more superficial layers
•tumor markers S-100, MART - 1 and HMB - 45
•most frequent mutations affect cell cycle control (including cell cycle control proteins p6/INK4a and p14/ARF) increases in RAS expression, or activation of telomerase
•Principles of Therapy: depends on stage-
Local: excision with wide margins
Local lymph node involvement: excision and adjuvant immunotherapy
Disseminated: immunotherapy, chemo and radiation