Non-Myxoid Solid Variant of Extraskeletal Myxoid Chondrosarcoma: An Underrecognized Subtype.

Introduction: Extraskeletal myxoid chondrosarcoma (EMC) is a rare sarcoma defined by NR4A3 gene rearrangements, typically featuring uniform cells with eosinophilic cytoplasm and mild atypia, arranged in cords or clusters within a chondromyxoid stroma. A cellular variant, characterized by increased cellular density and a solid growth pattern, has been recognized.

Methods: We encountered three cases of round cell sarcomas, diagnosed as EMC based on NR4A3 or NR4A2 rearrangements.

High-Grade Sarcomatous Transformation of Hybrid Hemosiderotic Fibrolipomatous Tumor-Myxoinflammatory Fibroblastic Sarcoma with Novel Gene Fusion.

Hemosiderotic fibrolipomatous tumor (HFLT) and myxoinflammatory fibroblastic sarcoma (MIFS) are rare, locally aggressive soft tissue tumors with a predilection for distal extremities of middle-aged adults. Hybrid tumors (HFLT-MIFS) demonstrate overlapping features of both and share recurrent translocation (1;10) (p22; q24). We describe a tumor with high-grade sarcomatous transformation of a hybrid HFLT-MIFS, with a novel gene fusion, presenting as a right foot soft tissue mass in an 85-year-old woman.

Assessing the Utility of DNA Methylation Profiling in the Classification of Myogenic Sarcomas of Bone.

The diagnosis of primary leiomyosarcoma (LMS) of bone is generally established based on integrative findings of morphologic features, immunohistochemical staining, and clinical and radiological findings. There are no specific genetic alterations that can be used to confirm the diagnosis of LMS in challenging diagnoses of bone sarcomas with myogenic differentiation. In this study, we assessed the utility of a DNA methylation-based classifier as an ancillary diagnostic tool for subclassifying bone sarcomas with myogenic differentiation.