CD34-Positive Spindle Cell Tumor With CTNNB1 Mutation: An Unusual Spindle Cell Variant of Sinonasal Glomangiopericytoma

Abstract

Sinonasal glomangiopericytoma is an uncommon mesenchymal tumor with a perivascular myoid phenotype, which is categorized as a borderline/low-grade malignant soft tissue tumor by the current World Health Organization Classification of Head and Neck tumors. Here, we present the case of a 53-year-old woman with an unusual spindle cell morphology of sinonasal glomangiopericytoma arising in the nasal cavity, mimicking solitary fibrous tumor. Microscopically, the tumor showed a cellular proliferation of spindle cells in fascicles including a focal long sweeping arrangement or whorls, or with a storiform growth pattern, associated with hemangiopericytoma-like gaping blood vessels embedded in a fibrous stroma. This arrangement of the spindle cells faintly indicated a solitary fibrous tumor rather than sinonasal glomangiopericytoma. Immunohistochemically, the tumor was positively reactive to not only beta-catenin (in the nuclei) but also CD34, although signal transducers and activators of transcription 6 was negative. Mutational analysis using Sanger sequencing detected a CTNNB1 mutation. We finally diagnosed the tumor as a sinonasal glomangiopericytoma, showing an unusual spindle cell variant. Such unusual spindle cell morphology with CD34-immunoreactivity potentially leads to an incorrect diagnosis of solitary fibrous tumor because such prominent fascicles including long sweeping structures, reminiscent of desmoid-type fibromatosis, have scarcely been described in the literature. Hence, careful morphological scrutiny using appropriate diagnostic adjuncts is necessary for correct diagnosis.

A case report of sinonasal glomangiopericytoma: An important reminder to always collect specimen

“…GPC diagnostic reliance on SMA positivity or CD34 negativity (not tested here) can be misleading as some cases have been shown to be SMA negative, 5 or CD34 positive. 15,16 These findings indicate that a panel of IHC tests is needed, as no single marker has been found to be sufficient for definitive GPC diagnosis. 4,5,[15][16][17]…”

“…15,16 These findings indicate that a panel of IHC tests is needed, as no single marker has been found to be sufficient for definitive GPC diagnosis. 4,5,[15][16][17]…”