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Division
East Florida
Hospital
HCA Florida Westside Hospital
Specialty
Pathology
Document Type
Poster
Publication Date
2024
Keywords
solitary fibrous tumor, neoplasms, benign, cancerous
Disciplines
Medicine and Health Sciences | Neoplasms | Pathology
Abstract
Introduction: Solitary Fibrous Tumor (SFT) is rare, especially in locations outside the pleura, and it can mimic benign mesenchymal tumors. Misdiagnosis, leading to inadequate treatment, can increase the risk of metastasis and recurrence. Dedifferentiated SFT (DD-SFT), is the most aggressive subtype.
Case Summary: A 45-year-old male presented with a rapidly growing, non-painful, palpable, exophytic right thigh mass. CT revealed an 8 x 7.4 x 7.0 cm heterogenous mass abutting the underlying muscle. His care team made a presumptive diagnosis of sarcoma, and referred him to a local oncologic surgeon who performed a radical excision and submitted the tumor to Pathology.
Results: Histologic examination revealed a biphasic zonal tumor with an abrupt transition from one zone consistent with a conventional SFT, to a second zone resembling a high-grade sarcoma. Immunohistochemically, only the cells in the conventional SFT zone stained positive for STAT6, BCL-2, and CD34. This sharp transition from conventional SFT to high-grade sarcoma, is characteristic of a dedifferentiated SFT. RNA sequencing detected the NAB2::STAT6 [inv (12;12)(12q13.3;12q13.3)] gene fusion, a diagnostic marker for SFT.
Discussion: The fusion of NAB2 to STAT6 replaces a repressor domain with a transactivation domain and correlates with high nuclear STAT6 staining in SFTs. However, areas that progress through dedifferentiation frequently lose expression of STAT6, along with other markers such as BCL-2 and CD34.
Conclusion: Inspecting enough tissue to identify the abrupt transition in histological architecture and staining pattern, can facilitate the identification of DD-SFT, inform treatment, and provide insight into developmental mechanism behind this malignant lesion
Original Publisher
HCA Healthcare Graduate Medical Education
Recommended Citation
Bender, Robert and Ferra, Susana, "Solitary Fibrous Tumor, Not Always the Pleura, Not Always Benign" (2024). East Florida Division GME Research Day 2024. 37.
https://scholarlycommons.hcahealthcare.com/eastflorida2024/37