Case Number : Case 2925 - 22 September 2021 Posted By: Saleem Taibjee

Neural vs. Myofibroblastic tumor, may be hyalinized myofibroma? Dermal Nodular Fascitis?

Epithelioid Fibrous Histiocytoma. ALK? Typical hyalinized stroma of older lesions and typical epidermal collarette

There are cellular and myxoid zones with spindle cells vaguely showing nested or whorled pattern. I think that this will require a battery of IHC stains. Mixed type of neurothekeoma comes to my mind.

Could this be a newly described spindle cell variant of epithelioid cell histiocytoma (spindle cell histiocytoma). IHC is needed. 

Kazlouskaya V, Ho J, Jedrych J, Karunamurthy A. Spindle cell variant of epithelioid cell histiocytoma (spindle cell histiocytoma) with ALK gene fusions: Cases series and review of the literature. J Cutan Pathol. 2021 Jul;48(7):837-841

Yes, absolutely spot on ... this is epithelioid fibrous histiocytoma, and I think could be justifiably deemed an example of the spindle cell variant. The ALK immunostain (positive) is shown below. There are frequently misdiagnosed as haemangiomas or melanocytic lesions clinically. The thigh seems to be a common anatomical site.

BW Saleem