Soft tissue sarcoma with ZC3H7B::BCOR fusion in a male mimicking low-grade fibromyxoid sarcoma - A case report.

Diagnosis of soft tissue tumors is often challenging, given the large number of entities, often with non-specific or overlapping morphology. Although morphology still plays an important part in diagnostic process, additional studies including immunohistochemistry and molecular genetics are often needed to arrive at correct diagnosis. We report a case of 61-year-old male with subcutaneous tumor in right hip area, that was surgically removed. The tumor was composed of uniform bland spindle cells in mild to moderately cellular myxoid nodules, with limited areas of collagenization and the diagnosis of low grade fibromyxoid sarcoma was made. The tumor recurred 3 years after the initial diagnosis and the new sample showed a high-grade round cell sarcoma with limited residual low-grade areas and non-specific immunoprofile after extended immunohistochemical work-up. Molecular analysis demonstrated ZC3H7B::BCOR fusion. Sarcomas with ZC3H7B::BCOR fusion occurring outside of uterus are exceedingly rare. A comprehensive review of previously published cases and a short discussion about classification of the entity is provided, together with data about morphology and immunoprofile of the lesions. The case also underscores the necessity of extended work up of soft tissue tumors with unusual immunohistochemical or morphological features in order to accurately assess their biological potential.