243 Solitary Fibrous Tumor/Hemangiopericytoma: A Case Report. (11th January 2018)

• Record Type: Journal Article
• Authors: Salib, Christian; Budhai, Alexandra; Kleinman, George
• Is Part Of: American journal of clinical pathology. Volume 149(2018)Supplement 1
• Page Start: S103
• Page End: S104
• Publication Date: 2018-01-11
• Subjects: Diagnosis, Laboratory -- Periodicals; Pathology -- Periodicals; 616.07
• DOI: 10.1093/ajcp/aqx123.242
• Languages: English
• ISSNs: 0002-9173

Abstract

Abstract: Solitary fibrous tumor/hemangiopericytoma is an increasingly recognized, combined term describing a spectrum of rare mesenchymal tumors. The term was introduced in the 2016 World Health Organization classification of tumors of the central nervous system following the discovery of a shared inversion at 12q13 between solitary fibrous tumors and hemangiopericytomas. This genomic alteration results in a NAB2/STAT6 gene fusion with resultant STAT6 nuclear expression. The resultant STAT6 immunopositivity is now necessary for diagnosis. While most commonly described in the pleura, orbit continues to be an uncommon extrapleural sites. Here, we present a case of a previously healthy 50-year-old man who presented with headache, dizziness, and a right CN IV palsy. MRI of the orbits demonstrated a large, enhancing, extra-axial mass within the right middle cranial fossa displaying marked mass effect on the adjacent temporal lobe and moderate vasogenic edema. Surgical resection revealed multiple irregular, pink-tan soft tissue fragments measuring 2 x 2 x 1.1 cm in aggregate. Microscopically, the specimen showed blood vessel proliferation with typical "stag horn" patterns. The vessels were surrounded by proliferating neoplastic round to oval cells with moderate pleomorphism, occasional nuclear atypia and high cellularity. Rare mitotic figures were seen (<5 per 10 hpf). Invasion of skeletal muscle and bone can be seen in some sections. Immunohistochemical analysis revealed the tumor cells were positive for STAT6 and CD34, with a low Ki67 mitotic index (1%-3%). This case is noteworthy for the rarity, atypically aggressive nature and presentation of this entity.