# Melanotrichoblastoma misdiagnosed as basal cell carcinoma: a case report

## TL;DR

A rare skin tumor called melanotrichoblastoma was mistaken for a different type of cancer, but was correctly identified through detailed tissue analysis.

## Contribution

This case report clarifies the diagnostic distinction between melanotrichoblastoma and basal cell carcinoma using histopathological features.

## Key findings

- Melanotrichoblastoma can resemble basal cell carcinoma clinically and under dermoscopy.
- Absence of retraction clefts in histopathology is a key feature distinguishing melanotrichoblastoma from basal cell carcinoma.
- Complete excision of the tumor led to no recurrence after two years.

## Abstract

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.