Epithelioid Fibrous Histiocytoma With an ETV6::NTRK3 Fusion in a Child: A Case Expanding the Spectrum of Receptor-Tyrosine Kinase Driven Epithelioid Fibrous Histiocytoma.
Bindu Challa, Rana Naous, Richard Kirschner et al.
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Case in brief
A 9-year-old girl presented with a 1.5 cm lesion on the right lateral chest wall. Histology showed a dermal nodule extending to the dermo-epidermal junction and into subcutis, composed of bland epithelioid and histiocytoid cells with a vaguely whorled pattern, prominent vessels, and focal myxoid stroma. There was no significant atypia, mitotic activity, or necrosis. Immunohistochemistry supported epithelioid fibrous histiocytoma (EFH), and targeted fusion analysis identified ETV6::NTRK3. The abstract does not report treatment or clinical outcome.
What made this case unusual
The tumor had classic EFH morphology but an ETV6::NTRK3 fusion, adding to the recognized molecular heterogeneity of EFH beyond its more typical ALK rearrangements.
Diagnostic / clinical pearl
EFH morphology is not limited to tumors with ALK rearrangements; targeted fusion analysis can identify other receptor tyrosine kinase fusions, including ETV6::NTRK3.