Superficial malignant ossifying fibromyxoid tumors harboring the rare and recently described ZC3H7B-BCOR and PHF1-TFE3 fusions.

Ossifying fibromyxoid tumor (OFMT) is a rare soft tissue neoplasm of uncertain differentiation and intermediate biologic potential. Up to 85% of OFMTs, including benign, atypical, and malignant forms, harbor fusion genes. Most commonly, the PHF1 gene localized to 6p21 is fused with EP400, but other fusion partners, such as MEAF6, EPC1, and JAZF1 have also been described. Herein, we present two rare cases of superficial OFMTs with ZC3H7B-BCOR and the very recently described PHF1-TFE3 fusions. The latter also exhibited moderate to strong diffuse immunoreactivity for TFE3. Reciprocally, this finding expands the entities with TFE3 rearrangements. Accumulation of additional data is necessary to determine if OFMTs harboring these rare fusions feature any reproducible clinicopathologic findings or carry prognostic and/or predictive implications.