# Basal Cell Carcinoma with Sarcomatoid Differentiation—A Rare Type and Its Possible Origin

## TL;DR

A rare case of basal cell carcinoma with sarcomatoid features is described, highlighting the need for detailed histological and immunohistochemical analysis.

## Contribution

This case report presents a rare instance of basal cell carcinoma with sarcomatoid differentiation and suggests possible epithelial–mesenchymal interactions in its origin.

## Key findings

- Histopathological and immunohistochemical analysis confirmed the presence of sarcomatoid differentiation in a basal cell carcinoma.
- The proximity of sarcomatoid cells to basaloid cells suggests potential epithelial–mesenchymal interactions in tumor development.
- The case emphasizes the importance of thorough evaluation for accurate diagnosis of rare tumor types.

## Abstract

Background: We present an interesting case involving a tumour comprising both basal cell tumour cells and sarcomatoid tumour cells. An 86-year-old woman presented with an erythematous lesion on her left cheek. Clinical and dermoscopic findings suggested BCC. Complete excision and histopathological examination revealed a BCC with a separate proliferation of atypical spindle and epithelioid cells. Immunohistochemical staining supported the diagnosis, with basaloid cells positive for CK5/6 and Ber-EP4 and sarcomatoid cells positive for CD10 and vimentin. Results: Histology and immunohistochemistry confirmed a basal cell carcinoma with sarcomatoid differentiation. The close proximity of sarcomatoid cells to the BCC component suggests a potential role of epithelial–mesenchymal interactions in tumour development. Further investigations into the exact origin of this tumour are required. Conclusion: Basal cell carcinoma with sarcomatoid differentiation is rare. This case highlights the importance of thorough histological and immunohistochemical evaluation. Further studies are necessary to better understand the pathogenesis of such collision tumours.