Case of mesenchymal tumor with the PPP6R3‐USP6 fusion, possible nodular fasciitis with malignant transformation

• Published in: Pathology international Vol. 69; no. 12; pp. 706 - 709
• Main Authors: Teramura, Yasuyo, Yamazaki, Yukari, Tanaka, Miwa, Sugiura, Yoshiya, Takazawa, Yutaka, Takeuchi, Kengo, Nakayama, Takayuki, Kaneko, Takao, Musha, Yoshiro, Funauchi, Yuki, Ae, Keisuke, Matsumoto, Seiichi, Nakamura, Takuro
• Format: Journal Article
• Language: English
• Published: Australia Wiley Subscription Services, Inc 01.12.2019
• Subjects: Case reports; Cell fusion; Cell proliferation; Disease control; Fasciitis; Fluorescence; Fluorescence in situ hybridization; Gene amplification; Gene fusion; Gene sequencing; Genetic transformation; Hybridization analysis; malignant transformation; Mesenchyme; nodular fasciitis; PPP6R3‐USP6; Regression analysis; Ribonucleic acid; RNA; RNA sequencing; Transformations; Tumors; RNA sequencing; nodular fasciitis; malignant transformation; gene amplification; PPP6R3-USP6
• ISSN: 1320-5463; 1440-1827
• DOI: 10.1111/pin.12851

Nodular fasciitis (NF) is a self‐limiting benign disease that is characterized by rapid proliferation of fibroblastic and myofibroblastic cells. The characteristic gene fusion containing the USP6 gene is a genetic hallmark of NF and MYH9‐USP6 is the most frequent fusion, suggesting that NF is not a reactive condition but a neoplastic disease. Malignant transformation of NF has been reported rarely as a single case associated with the PPP6R3‐USP6 fusion. Here we report a case of soft part tumor of which the histological feature was a typical NF but showed aggressive and non‐regressing growth with local invasion. Targeted RNA sequencing and fluorescence in situ hybridization analysis identified PPP6R3‐USP6 with gene amplification. These findings indicate that the present case is the second case of malignant NF, and we suggest potential malignant transformation in certain NF cases.