{Reference Type}: Case Reports
{Title}: Case of mesenchymal tumor with the PPP6R3-USP6 fusion, possible nodular fasciitis with malignant transformation.
{Author}: Teramura Y;Yamazaki Y;Tanaka M;Sugiura Y;Takazawa Y;Takeuchi K;Nakayama T;Kaneko T;Musha Y;Funauchi Y;Ae K;Matsumoto S;Nakamura T;
{Journal}: Pathol Int
{Volume}: 69
{Issue}: 12
{Year}: Dec 2019
{Factor}: 2.121
{DOI}: 10.1111/pin.12851
{Abstract}: 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.