Basal Cell Carcinoma (BCC)

 

Common sites:

    • Sun-exposed sites
    • Not mucosal surfaces

 

Gross features:

    • Pearly
    • Telangiectasias

 

Histologic features:

    • uniform tumour cells resembling normal basal cell layer of epidermis
    • pallisading edges
    • separation artifact between stroma and nests
    • may have numerous mitotic figures
    • abundant apoptosis
    • mucin deposition in stroma
    • nodular (most common):
      • cords and islands
      • growing deep into dermis
      • variably basophilic cells
      • hyperchromatic nuclei
      • embedded in a mucinous matrix
      • often surrounded by many fibroblasts and lymphocytes
    • multifocal superficial type:
      • multifocal growths originating from the epidermis
      • do not extend below superficial dermis (unless associated with another type of BCC)
      • extending over several square centimeters of skin surface
    • sclerosing type (morphea type):
      • slender nests
      • deeply infiltrative
      • reactive (++inflammatory cells) stroma composing >50% of the tumour bulk
    • keratotic type:
      • often misdiagnosed as squamous cell carcinoma
      • keratinization present
      • numerous apoptotic keratinocytes
      • relatively regular cytologic features
      • abundant stroma
    • keratotic (infundibulocystic, pilar) type:
      • differentiation towards hair follicle infundibulum
      • continuity with overlying epidermis and adjacent hair follicles
      • budlike structures as well as follicular bulbs and dermal papillae
      • solid and reticulated pattern of growth
      • squamous-appearing basaloid cells with amphophilic cytoplasm
      • cysts lacking a granular cell layer filled with keratin and parakeratotic material
    • ulcerated BCCs often have superficial keratinization
    • may be pigmented (melanin) = pigmented type
      • symbiotic non-tumoral proliferating melanocytes
    • may produce mucin
      • intralobular and stromal collections (basophilic)
      • cells with a signet ring appearance
    • may have amyloid deposition (50-75%)
    • may hav e glandular pattern (adenoid type)
    • may have sebaceous differentiation
    • may be largely cystic
    • may have granular or clear cytoplasm
    • amyloid may be present in large quantities

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

CK5

 

 

CK14

 

 

 Ber-EP4

 

 

 

Molecular features:

    • X chromosome inactivation
    • PATCHED gene mutations

 

Other features:

    • rarely metastasize
    • increased risk of recurrence in sclerosing and superficial types
    • multiple BCCs in Basex syndrome and Gorlin’s syndrome (Nevoid basal cell carcinoma syndrome)
    • adverse prognostic factors:
      • histologic subtypes:
        •  infiltrative subtype
        • morpheaform (sclerosing) subtype
        • micronodular subtype
      • invasion into deep subcutaneous fat, muscle, or cartilage
      • perineural invasion
      • surgical margin positivity
      • presence of scar within tumour

 

References:

    • Essentials of AP 2006
    • Sternberg 2004