Basal cell carcinoma misdiagnosed as trichoepithelioma.

Trichoepithelioma is a benign hair follicle tumor that can undergo malignant transformation into basal cell carcinoma in rare cases. Due to the similar clinical and histological features of trichoepithelioma and basal cell carcinoma, distinguishing between these types of tumors can be a diagnostic challenge. Punch biopsy obtains only a small sample of the entire lesion, and thus inherently involves a risk of misdiagnosis between histologically similar diseases. Therefore, if the possibility of misdiagnosis can reasonably be suspected, clinicians should conduct an excisional biopsy or immunohistochemical staining (e.g., CD10 and Bcl-2) to ensure an exact diagnosis. Although trichoepithelioma is benign, the surgical excision of solitary trichoepithelioma should be considered in order to avoid the possibility of malignant transformation, which has occasionally been documented for multiple familial trichoepitheliomas. Herein, we report a case that was initially misdiagnosed as trichoepithelioma before ultimately being diagnosed as basal cell carcinoma through excision and immunohistochemical staining.