Trichoblastoma arising within an apocrine poroma.

A poroma is a benign neoplasm composed of poroid and cuticular cells and is thought to derive from the eccrine duct. Several recent reports have described cases with sebaceous, follicular, and apocrine differentiation, suggesting a possible apocrine origin, however. Trichoblastoma is a rare benign tumor composed of germinative cells related to the folliculosebaceous-apocrine unit. We report a unique case of a trichoblastoma arising within a poroma with apocrine and sebaceous differentiation. To our knowledge, this exceptional association has not been described previously and may support the theory of the apocrine origin of poromas.