Florid Proliferation of Hyalinized Vessels in a Spermatic Cord STAT6 Positive Solitary Fibrous Tumor and Its Potential Clinical Implications

Abstract

A solitary fibrous tumor (SFT) arising in the paratesticular region is a rare event. Typically most SFTs present as a lung mass and have a characteristic microscopic appearance. Although uncommon, SFTs may present at just about any anatomical site. Here we present a case of a SFT arising along the right spermatic cord, with histologic features mimicking a cellular angiofibroma. We describe the diagnostic immunohistochemical markers useful for arriving at its diagnosis. We also summarize our current understanding of the structural and molecular features that make up SFTs and discuss how these features may help us better understand the pathophysiology of pluripotent mesenchymal stem cell differentiation.

Shapeshifters in Pathology: Paratesticular Solitary Fibrous Tumor Mimicking Leiomyoma

“…2 These tumors are very rare in the scrotal/paratesticular region, with only 15 cases having been reported in the literature to date. 7,8 To our knowledge a paratesticular SFT mimicking leiomyoma on morphology and IHC has not been reported. This unique finding has two possible explanations: 1) the entrapment phenomenon, and 2) tumor origin from mesenchymal stem cells disproportionately differentiating toward smooth muscle cells.…”

“…Given these facts, the possibility of diversity in the morphology of SFT ought to be kept in mind by the diagnostician, and STAT6 immunohistochemistry should be sought on spindle cell tumors where there is even the slightest suspicion of SFT, as it is highly sensitive and specific for this entity. 7,[11][12][13] One caveat to this, however, is that de-differentiated liposarcomas may also resemble SFT morphologically and may also express STAT6, but usually in a more variable, limited fashion. 14…”

“…This unique finding has two possible explanations: 1) the entrapment phenomenon, and 2) tumor origin from mesenchymal stem cells disproportionately differentiating toward smooth muscle cells. 7,9,10 The first hypothesis is based on SFTs known predilection for infiltrating background tissues which in rare instances could create the appearance of heterogeneous tumor elements. This occurrence has been previously reported in the lung, with SFT surrounding islands of normal lung tissue as well as in the salivary gland, where SFT surrounded and entrapped benign ducts.…”