Rapidly fatal SMARCA4-deficient undifferentiated sarcoma originating from hybrid hemosiderotic fibrolipomatous tumor/pleomorphic hyalinizing angiectatic tumor of the foot

Pleomorphic hyalinizing angiectatic tumor (PHAT) of soft parts and hemosiderotic fibrolipomatous tumor (HFLT) are two rare low-grade locally recurring neoplasms with predilection for the foot/ankle. Recent studies support a close link between the two entities, and origin of PHAT from HFLT and occurrence of hybrid HFLT/PHAT have been documented. Both lesions often harbor TGFBR3 or MGEA5 rearrangements. Rare sarcomas originating from HFLT/PHAT have been reported, typically resembling myxofibrosarcoma or myxoinflammatory fibroblastic sarcoma. We describe a novel SMARCA4-deficient undifferentiated sarcoma with rhabdoid features originating from hybrid HFLT/PHAT in the foot of a 54-year-old male. The tumor pursued a highly aggressive course with rapid regrowth after resection and multiple metastases resulting in patient’s death within 5 months, despite systemic chemotherapy. Immunohistochemistry revealed SMARCA4 loss in the undifferentiated sarcoma, but not in the HFLT/PHAT. Molecular testing confirmed TGFBR3/MGEA5 rearrangements. This report expands the phenotypes of sarcomas developing from pre-existing PHAT/HFLT.

Pleomorphic Hyalinizing Angiectatic Tumor (PHAT): Review of the Literature with Case Presentation

Pleomorphic hyalinizing angiectatic tumor (PHAT) is a very rare entity of soft tissue considered a “neoplasm of uncertain behaviour of connective or other soft tissue” by the World Health Organization (2020). It develops in subcutaneous tissue of the lower extremities, more frequently in the region of the ankle and foot, and rarely as a deep-seated soft tissue mass in locations such as the perineum, buttock, arms, head and neck, and viscera. Although inconsistent cytogenetic data have been reported on PHAT so far, there are potential morphological and genetic overlaps with hemosiderotic fibrolipomatous tumor (HFLT) and myxoinflammatory fibroblastic sarcoma (MIFS). Here we report a case of PHAT at the level of the upper third of the right thigh in a 48-year-old patient and we also focus on the differential diagnoses of these entities and conduct a literature review of reported cases.

A Subcutaneous Pleomorphic Hyalinizing Angiectatic Tumor of Soft Parts of the Right Ankle: A Case Report

Abstract- Pleomorphic hyalinizing angiectatic tumor (PHAT) is a rare, slow-growing mass, which is locally aggressive and classified as tumors of borderline malignancy. In this study, we report a case of subcutaneous ankle mass in 43-year-old female since 2 years ago with a pathological diagnosis of PHAT, characterized by clusters of ectatic, fibrin-lined, and thin-walled vessels which are surrounded by a spindled or pleomorphic neoplastic stroma.