Pigmented basal cell carcinoma: Cytological diagnosis and differential diagnoses
A 55-year-old female presented with a painless, non-hairy mole on the dorsal aspect of left thigh which had progressively increased over a period of 5 years. Local examination revealed a hyperpigmented polypoid swelling measuring 3 × 2 × 2 cm. It was firm, non-tender and the surface was focally ulcerated with bleeding points []. General physical examination and systemic examinations were normal. There was no regional lymphadenopathy. FNA from the swelling yielded a brownish tinged hemorrhagic aspirate. Smears prepared were highly cellular showing many syncytial branching epithelial fragments laid in a clean background, with few having club-shaped edges. The cells were small basaloid, having scant cyanophilic cytoplasm, indistinct cell borders, and rounded hyperchromatic nuclei showing mild anisonucleosis, coarse granular chromatin and inconspicuous nucleoli. Occasional mitotic figures were seen. At places the fragments showedsmooth external contours with peripheral palisading of the nuclei. Many epithelial fragments showed cells embedded in abundant pink basement membrane like matrix. Fair amount of blue-black pigment was seen in the cellular fragments as well as in the macrophages scattered in the background []. This pigment stained positive for Masson's Fontana stain. A cytological diagnosis of pigmented basal cell carcinoma was offered and excision biopsy advised.\nExcision with 1 cm margin was performed under aseptic conditions. Gross specimen consisted of a skin covered polypoidal tissue measuring 3 × 2 × 2 cm. the cut surface was solid, firm, grey white with areas of brown-black pigmentation. Overlying skin was focally ulcerated with presence of hemorrhagic crusts.\nMicroscopic examination revealed a circumscribed dermal tumor, arising from the base of the epidermis, consisting of small basaloid cells exhibiting varied morphology. Predominant pattern was adenoid-basal with the tumor islands containing intertwining strands of epithelial cells forming gland-like structures at places (that contained loose mucoid stroma within them) []. Other patterns included micronodular; infundibulocystic and fibroepithelioma-like []. The cells were showing peripheral palisading at places. Some of the tumor cells showed melanin pigment production along with abundant melanin pigment in the melanophages present in the stroma surrounding the tumor cells. Occasional mitotic figures were seen however there was no necrosis, perineural/lymphovascular invasion. All surgical margins were free of tumor. On immunohistochemistry, the tumor cells were positive for Bcl-2, CD 10 and Ber EP-4 [], while EMA and HMB-45 was negative. S-100 was positive in the pigmented cells and melanophages while it was negative in rest of the cells. A final diagnosis of pigmented basal cell carcinoma (mixed histology) was rendered. The patient is well 6 months after the surgical excision with no recurrence.