Table 3.
Clinically Relevant BCC Subtypes and Their Morphological Traits
| Clinically Relevant BCCs | Histopathology Traits |
|---|---|
| Nodular | Deep dermis extension of malignant basaloid cells arranged as large nests/islands with peripheral palisading and central, disorganized cell arrangement with apoptotic cells; tumor-stroma separation (clefts), mucoid or myxoid stroma with spindle cells (sometimes with a keloidal or collagenous aspect), ± amyloid deposits secondary findings: centrally located mature keratin areas (keratotic), cystic degeneration (cystic/nodulocystic), cribriform display of tumor cells (adenoid) |
| Superficial | Superficial dermis extension of malignant basaloid cells connected to the epidermis and arranged as small islands/lobules with peripheral palisading, with myxoid stroma and a lichenoid, chronic, band-like inflammatory infiltrate ± multicentric tumor ± associated patterns: micronodular, nodular, or infiltrating |
| Infiltrating | Deep dermal or hypodermal small/thin irregular islands/nests/chords of malignant tumor cells (1 to 8 cells in thickness), sometimes angulated with apparent permeating invasion pattern, bordered by a narrow margin of stroma, parted by normal collagen, rarely with tumor-stroma clefting |
| Infundibulocystic (with adnexal differentiation) | Has follicular, apocrine, eccrine or sebaceous gland differentiation matrical differentiation = presence of shadow cells infundibulocystic variant = small infundibular cyst-like spaces in the basaloid nodules sebaceous differentiation = mature sebocytes eccrine/apocrine sweat gland differentiation = ductal structures (+ decapitation secretion = apocrine differentiation) |
| Basosquamous/metatypical | Features common to both BCC and squamous cell carcinoma, with transitioning zones in-between tumor nests of basaloid cells are intermingled with eosinophilic, atypical squamous cells which are focally or diffusely distributed in the tumor mass highly cellular stroma (most often), fibrotic |
| Fibroepithelial (fibroepithelioma of Pinkus/Pinkus tumor) | Narrow strands of intermingling malignant basaloid cells set in a reticular pattern, with epidermal link, inside a fibroblastic stroma. ± basaloid islands (rarely) |
| With sarcomatoid differentiation (metaplastic carcinoma) | Malignant basaloid cells resting in a sarcomatous stroma with variable histology the stromal malignant mesenchymal component: leiomyosarcoma, osteosarcoma, chondrosarcoma, rhabdomyosarcoma, pleomorphic undifferentiated sarcoma. |