Abstract
We report two cases of trichoblastoma with significant keratin 20 positive cells. One patient was 21-year-old female who had a pinkish nodule and a subcutaneous nodule on her right neck. It presented a “showman-like” appearance. The other patient was 73-year old male who had a brownish nodule with a small, brown-to-purple papule on its top. It presented a “nipple-like” appearance. Both cases showed the “pop-put” phenomenon when surgical resections were performed. Histologically, both tumors were symmetrical and well circumscribed. There were numerous aggregations of germinative cells in the dermis to the subcutis. Immunohistochemically, these tumors showed large numbers of keratin-20 positive cells in the aggregations. We also examined five cases of nodular basal cell carcinoma. None of these were positive for keratin-20. The significance of keratin 20-positive cells in trichoblastoma and their usefulness for differentiation between trichoblastomas and basal cell carcinomas were discussed.
