Non

Non-Melanoma Skin Cancers

Skin cancer accounts for 50% of all new human cancers – more than breast, prostate, lung, and colon combined

One million new cases annually – 80% BCC, 15% SCC, 4% melanoma – 9200 deaths (80% from melanoma)

most significant risk factor for all skin cancers is UV light (DNA mutated CÞ T or CCÞ TT) and fair skin

Basal Cell Carcinoma (BCC) – a tumor differentiating toward basal cells

Incidence – most common cancer in humans – 4x as common as squamous cell, 20x as common as melanoma

more common in males and fair skinned individuals – 40% of BCC patients will have another BCC within 10 years

Etiology – radiation (UV or ionizing), genodermatoses (linear BCC, basal cell nevus syndrome, Basex syndrome)

genetic basis – 90% of BCC tumors have mutation in p53, 90% have mutation in patched (involved in morphogenesis)

Clinical Appearance – seven presentations:

Histology – three patterns: (1) nodular, (2) superficial multicentric, (3) morphea

Management Considerations – treatment plan depends upon number, size, and borders of tumors, also age of patient

location is important: those occurring along embryonic fusion planes (esp. the midface) are often deeply invading
recurrent tumors are much more aggressive than initial tumors

Treatments:

electrodessication and curettage (scraping and burning – tumor is softer than surrounding skin)
excision
cryosurgery (freezing)
topical chemotherapy (especially 5-fluorouracil)
radiation
Moh’s micrographic surgery (see below)

Squamous Cell Carcinoma (SCC) – cancer cells mimic higher cell layers, with keratin

Incidence – steadily increasing – mostly males, older, and fair skinned individuals

Etiology: radiation (UV or ionizing), genodermatosis, human papilloma virus, immunosuppression, arsenic (in well water), polycyclic aromatic hydrocarbons, chronic ulcer/scar (fertile soil for SCC)

other common mutations: p16 (cell cycle regulation), beta-catenin (signal transduction)

actinic keratosis – most common precursor – from UV light, pink scaly macule – easier to feel than see

Bowen’s disease – in situ (not through basement membrane); erythroplasia of Queyrat is Bowen’s in penis

Clinical Appearance – no distinct clinical appearance, often plaques or nodules with scale, crust, erosion, ulceration

Histology – four types: (1) conventional (differentiated), (2) spindle cell, (3) acantholytic (pseudoglandular), (4) verrucoid

all have eosinophilic cytoplasm (from keratin) and "keratin pearls"
also graded based upon Broder’s classification – I to IV, correlates with clinical outcome

Modes of Spread - expansion and infiltration; shelving or skating; conduit spread; metastasis

Management Considerations – often spread along conduit (e.g., nerve sheet through paraneural invasion)

primary SCC has low metastatic potential (2-6%) unless it has high-risk characteristics

high-risk SCC: lower lip or ear, growth on ulcer, scar, or radiated site, recurrent or rapid growth, large (>2cm), deep (below reticular dermis), poor differentiation, perineural invasion

Moh’s Micrographic Surgery

Procedure of choice for high-risk BCC or SCC (esp. large, near ear/nose/other vital structures, recurrent, aggressive histo)

skin is excised in plane parallel to skin surface in a frozen section and tumor is mapped until entire tumor removed
often find tumor to be much larger than originally expected (exception: nodular BCC)

Prevention and Future Considerations

Prevention of Non-Melanoma Skin Cancer: sun protection, ozone layer, ? Retinoids

Future Considerations: photodynamic therapy; immunotherapy; laser therapy; multicenter, randomized studies