Ossifying fibromyxoid tumor (OFMT) of the soft parts is a mesenchymal neoplasm of uncertain lineage. Fibromyxoid matrix and peripheral metaplastic bone are common histological features of this type of tumor. In the present study, a case of OFMT in a 33-year-old female was reported. The patient was referred to the First Affiliated Hospital of China Medical University (Shenyan, China) in January 2018. The patient had developed a mass in the left upper arm 6 months prior to presentation, which was slowly enlarging. The tumor was 1.5 cm in diameter, with hard texture. Histologically, the tumor showed a clear boundary with no invasion into the adjacent tissue. The majority of tumor cells were round and medium-sized, with abundant pale cytoplasm, without obvious atypia and densely arranged in sheets. The tumor tissue was characterized by cartilage-like morphology and fibromyxoid and hyalinization matrix. Mitotic index was <1/10 high-power fields. Additionally, tumor cells were positive for S-100 and vimentin expression, but negative for smooth muscle actin, CD34, cytokeratin, desmin, human melanoma black 45 and melanoma A. Ki67 index was ~1%. The patient underwent surgery and the tumor was totally removed. No recurrence was observed at the final 6-year follow-up. Based on the aforementioned findings, the patient was diagnosed as typical OFMT. Slow growth and clear boundaries often suggest an indolent nature to this type of tumor. However, close follow-up should be performed due to its malignant potential.
Keywords: case report; ossifying fibromyxoid tumor; upper arm.
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