Pocket Oncology (Pocket Notebook Series), 1st Ed.

BASAL AND SQUAMOUS CELL CARCINOMAS

Parisa Momtaz and Allan C. Halpern

Epidemiology

• Most common CA in US; collectively known as nonmelanoma skin CA

• BCC is 5× more common than SCC

• Rarely met, however, can be locally aggressive & disfiguring; SCC w/greater potential for met

Risk Factors/Pathogenesis

• Sunlight: UVB strongly correlated w/SCC; correlation w/BCC is more complex

• Fair-skinned individuals at greatest risk

• Radiation exposure at a young age

• Prolonged PUVA exposure

• Immunosuppression (organ transplantation)

• For SCC, other RFs include HPV (types 16, 18, 31, 33, 38), chemical carcinogens

• SCC arise from keratinocytes

• Most BCC arise from the epidermal cells differentiated in the primitive hair bulb

Genetics

• Mts in BCC frequently involve the PATCH gene or members of the sonic hedgehog signaling pathway → overexpression of transcription factor Gli 1

• Specific UV-induced Mts in the tumor suppressor p53 gene

• Genetic syndrome predispose to BCC, SCC: Albinism, xeroderma pigmentosum, Nevoid BCC syndrome

• Nevoid BCC syndrome (aka basal cell nevus syndrome, Gorlin–Goltz syndrome)

Clinical Features

• Most develop on head & neck (80%) & are more likely to recur compared to lesions developing on the trunk or extremities

• SCC can arise on mucous membranes, BCC do not

• SCCs appear as hyperkeratotic papules or plaques often w/crust or ulceration

• SCC precursor lesions: Actinic keratoses, cutaneous horn, keratoacanthoma

• Bowen Disease: SCC in situ on the skin

• Basosquamous carcinomas: Mixed histology of both BCC & SCC; classified under SCC & risk of met determined by the squamous component

Diagnosis

• Complete skin examination, including mucous membranes

• LN evaluation (for SCC; FNA or core bx if enlarged)

• Bx (should include deep reticular dermis)

• Imaging if extensive disease (bone, perineural, or lymphovascular invasion)

Staging: BCC and SCC

Treatment Localized Disease: BCC, SCC

• Surgical excision w/histologic control of margins: Excision w/POMA, Mohs surgery

• Electrodessication & curettage for low-risk lesions

• Cryotherapy for pre-SCC lesions

• LND if regional LN involvement

• Adjuvant RT for pts who have undergone LND; o/w use of radiation Rx controversial; consider for positive margins, evidence of substantial perineural involvement

• Superficial therapies: 5-FU, imiquimod, PDT

Treatment Metastatic Disease: BCC

• Rare; however, systemic chemotherapy is indicated

• Clinical trials

• Vismodegib, inhibitor of the hedgehog pathway for residual or met disease (NEJM 2012;366:2171)

• Platinum-based chemotherapy regimens

Treatment Metastatic Disease: SCC

• Limited data; CIS-based regimens, cetuximab

• Clinical trials

• If transplant pt on immunosuppressive Rx, can consider adjusting dose of immunosuppressive Rx if appropriate

Prognosis and Follow-up

• Localized disease has good prognosis

• Worse prognosis for SCC of the genitalia, mucous membranes

• Perineural involvement increases the risk of recurrence for BCC & SCC & increases met risk for SCC

• Close surveillance for high-risk pts (immunosuppression, organ transplantation)

• Encourage sun protection strategies & self skin checks

• Pts w/h/o BCC or SCC are likely to develop more lesions; perform annual or bi-annual skin exams

Figure 16-1 SCC courtesy of Dr. Allan Halpern (MSKCC)

Figure 16-2 BCC courtesy of Dr. Allan Halpern (MSKCC)