Case Report: Infiltrative granular cell basal cell carcinoma of the nasal ala: a diagnostic pitfall associated with focal PRAME immunoreactivity in a small biopsy

Granular cell basal cell carcinoma (GCBCC) is a rare histologic variant of basal cell carcinoma (BCC) that may mimic other granular cell lesions and melanocytic neoplasms. A 57-year-old woman presented with an ulcerated lesion on the left nasal ala. Biopsy showed infiltrative BCC with prominent granular cell change. Tumor cells were immunoreactive for BerEP4, CD10, p40, and CK5/6 and negative for S100. Focal PRAME immunoreactivity was also present in the biopsy; however, because SOX10 and Melan-A were not performed and serial-section correlation was unavailable, its cellular source could not be established, and colonizing melanocytes could not be excluded. The patient subsequently underwent Mohs micrographic surgery. Frozen sections from all four submitted margins were negative for carcinoma, and final pathology supported BCC, with a maximum horizontal tumor extent of approximately 6 mm, an invasion depth of approximately 1.2 mm, and no lymphovascular or perineural invasion. Focal PRAME immunoreactivity in a small biopsy should therefore be interpreted cautiously and only in conjunction with morphology and lineage-specific immunohistochemistry.