Cytologic features of metastatic sebaceous carcinoma: report of two cases with comparison to three cases of basal cell carcinoma.

The cytologic findings of two cases of metastatic sebaceous carcinoma are described and compared to three cases of locally recurrent basal cell carcinoma. Morphological findings for sebaceous carcinoma in fine-needle aspiration biopsy (FNAB) smears included cellular, loosely cohesive cell clusters with central necrosis, squamous pearl formation, and adjacent keratin debris. The tumor cells had moderate amounts of vacuolated cytoplasm, round to oval vesicular nuclei with clumped chromatin, nucleoli, some nuclear overlap, and numerous mitotic figures. An interesting finding was the presence of numerous multinucleated giant cells, probably responding to extravasated lipid or keratin material. In contrast, the FNAB smears of basal cell carcinoma typically were less cellular, with more tightly cohesive and smaller clusters of uniform hyperchromatic basaloid cells with high nuclear to cytoplasmic ratios, and a narrow rim of cytoplasm without vacuolization. The morphologic features of sebaceous carcinoma in FNAB smears appear to be distinct from those of basal cell carcinoma. FNAB can be a useful preoperative diagnostic technique to distinguish these two cutaneous malignancies.