Myxofibrosarcoma Initially Presenting as a Pleomorphic Hyalinizing Angiectatic Tumor (PHAT): is PHAT a Precursor or Unique Type of Myxofibrosarcoma?

Myxofibrosarcoma (MFS) is a common soft tissue sarcoma of adults. We present an unusual case which initially showed features of a pleomorphic hyalinizing angiectatic tumor (PHAT). The lesion was characterized by abundant plump, eosinophilic cells exhibiting striking nuclear atypia, set in a dense, hyalinized stroma with a prominent, angiectatic vasculature. Rare mitotic figures were identified. These findings were felt to be most consistent with the diagnosis of PHAT. Four months after removal, local recurrence was noted, which demonstrated findings of a high grade MFS, including a cellular proliferation of pleomorphic spindle cells set in a prominent myxoid stroma. Multiple mitoses, including atypical ones, were present. In light of these findings, the original specimen was reexamined and the diagnosis was revised to high‐ grade MFS. MFS, especially low‐grade lesions, may be confused with several benign lesions. Previous cases mimicking PHAT have not been reported. We describe a unique case of high‐grade MFS which initially showed characteristic features of a PHAT, raising the possibility that MFS may occasionally arise in, or have areas that masquerade as, PHAT. It is possible that PHAT, currently considered a benign neoplasm, may actually represent a peculiar form of MFS of low malignant potential.