Sclerotic Epithelioid Dermatofibroma With Cytokeratin Expression

Area of Science:

• Dermatopathology
• Oncology
• Histology

Background:

• Dermatofibromas are common benign skin lesions with diverse histological presentations.
• The sclerotic and epithelioid variant is exceptionally rare, with limited documented cases.

Purpose of the Study:

• To report the first case of sclerosing epithelioid dermatofibroma with diffuse cytokeratin and p40/p63 expression.
• To highlight the importance of recognizing this atypical immunophenotype to prevent misdiagnosis.

Main Methods:

• Histopathological examination of a 1-cm erythematous plaque on the chest.
• Immunohistochemical analysis of neoplastic cells for various differentiation markers.

Main Results:

• The lesion showed epithelioid cells amidst hyalinized collagen bundles.
• Immunohistochemistry revealed positivity for factor XIIIa, CD68, vimentin, cytokeratins (AE1/AE3, CK8/18), p40, and p63.
• Negative markers for muscle, vascular, melanocytic, and neural differentiation were noted.

Conclusions:

• This is the first reported sclerosing epithelioid dermatofibroma with diffuse cytokeratin and p40/p63 expression.
• The aberrant immunophenotype may mimic malignant neoplasms like sarcomatoid squamous cell carcinoma or epithelioid sarcoma.
• The observed expression pattern likely represents phenotypic plasticity, not true epithelial malignancy.