Melanotrichoblastoma misdiagnosed as basal cell carcinoma: a case report

Melanotrichoblastoma (MTB) is an exceptionally rare benign adnexal tumor with follicular differentiation. Its clinical and dermoscopic resemblance to pigmented basal cell carcinoma (BCC) often leads to misdiagnosis.

A 51-year-old male presented with a slow-growing, blue-black nodule on the right canthus that had been present for five decades, with recent central ulceration. Dermoscopy revealed homogeneous pigmentation with atypical blue-white areas and dilated vessels, suggestive of BCC. Histopathological examination showed well-demarcated dermal nests of basaloid cells with peripheral palisading and stromal pigment deposition. Importantly, retraction clefts were absent, a key feature distinguishing MTB from BCC. The lesion was completely excised, with no recurrence after two years.

This case highlights the diagnostic challenge of MTB. Histopathology remains the gold standard for differentiation, wherein the absence of retraction clefts serves as a pivotal diagnostic clue. Increased awareness of MTB is essential to avoid misdiagnosis and ensure appropriate, conservative management.