Epithelioid Fibrous Histiocytoma (EFH) With Rare PPFIBP1-ALK Fusion: A Predominantly Spindle Cell Variant Within the Emerging Spectrum of Myxoid Spindle Cell EFH

TL;DR

This paper describes a rare case of a benign tumor with a specific genetic fusion and spindle cell features, expanding the known spectrum of a recently identified tumor type.

Contribution

The paper presents a rare PPFIBP1-ALK fusion case in a spindle cell variant of EFH, contributing to the emerging classification of myxoid spindle cell EFH.

Findings

A 56-year-old male had a spindle cell variant of EFH with PPFIBP1-ALK fusion.

Immunohistochemistry showed ALK and other marker expressions consistent with EFH.

The case is classified within the myxoid spindle cell EFH spectrum (SAMS).

Abstract

Epithelioid fibrous histiocytoma (EFH) is a benign fibrohistiocytic neoplasm characterized by morphologic heterogeneity and recurrent anaplastic lymphoma kinase (ALK) gene rearrangements. We present a rare case of EFH located on the lateral neck of a 56-year-old male patient, demonstrating a predominantly spindle cell morphology. Immunohistochemical analysis revealed granular cytoplasmic positivity for ALK, along with expression of CD68, CD4, epithelial membrane antigen, caldesmon, and smooth muscle actin. Next-generation sequencing confirmed the presence of a rare PPFIBP1-ALK fusion. The presented case highlights a predominantly spindle cell variant of EFH and suggests inclusion within the recently described myxoid spindle cell EFH spectrum, which encompasses the superficial ALK-rearranged myxoid spindle cell neoplasms (SAMS).

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