Epithelioid Fibrous Histiocytoma: A Concise Review

Area of Science:

• Dermatopathology
• Molecular pathology
• Oncology

Background:

• Epithelioid fibrous histiocytoma (EFH) is a rare skin neoplasm.
• EFH is often considered a variant of dermatofibroma but exhibits distinct epithelioid morphology.
• The molecular relationship between EFH and dermatofibroma is poorly understood.

Purpose of the Study:

• To investigate the molecular underpinnings of Epithelioid Fibrous Histiocytoma (EFH).
• To determine if EFH is a distinct entity from benign fibrous histiocytoma (dermatofibroma).
• To identify potential diagnostic molecular markers for EFH.

Main Methods:

• Molecular studies including analysis of gene rearrangements.
• Comparison of molecular findings in EFH versus benign fibrous histiocytoma.
• Histopathological evaluation of EFH for diagnostic mimicry.

Main Results:

• Recurrent anaplastic lymphoma kinase (ALK) gene rearrangements were identified in EFH.
• These ALK gene rearrangements have not been previously described in benign fibrous histiocytoma.
• EFH exhibits cytomorphology that can mimic vascular and melanocytic neoplasms.

Conclusions:

• The presence of ALK gene rearrangements highlights the biological uniqueness of EFH.
• EFH may represent a distinct entity separate from benign fibrous histiocytoma.
• Molecular findings, particularly ALK rearrangements, can serve as a diagnostic tool to differentiate EFH from its mimics.