Image Quiz: Cytology-A mysterious temporal mass after limb amputation

Benign epithelial tumor is correct!

The extremely tight cohesiveness of these cells and their tendency to form sheets and trabecular structures, with few cells free in the background, identifies them as epithelial cells. Their uniformity, with minimal anisocytosis (variation in cell size), little anisokaryosis (variation in nuclear size), and no visible nucleoli, makes it likely that this is a benign tumor. These cells have a high nuclear-to-cytoplasmic ratio, with only a thin rim of lightly basophilic cytoplasm separating the nuclei. These features are suggestive of a basilar-type tumor arising from either the basal cell layer of the epidermis (basal cell tumor) or from a hair follicle. In this case, histologic examination of a biopsy sample revealed a trichoblastoma, a benign follicular tumor.