Huge Trichilemmal Carcinoma With Metastasis Presenting With Two Distinct Histological Morphologies: A Case Report

BACKGROUND: Trichilemmal carcinoma (TC) is a rare malignancy of cutaneous adnexal carcinoma, with only 136 cases reported in the literature to date. It usually has an indolent course and benign clinical evolution, and only four cases with regional and distant metastasis have been reported. Tumor cells present with the characteristics of trichilemmal differentiation on both histological and immunohistological examination. CASE PRESENTATION: We report a case of TC on the scalp with an aggressive course and metastasis to the ipsilateral neck. Moreover, the lesions presented with two distinct histological morphologies. CONCLUSION: Despite an indolent course and benign clinical evolution, TC has the potential for local invasion and recurrence, which implies that accurate early diagnosis and careful follow-up are very important for these patients. More than one specimen should be obtained for histopathological examinations when the lesion is very large and characterized by different morphologies.