Pleomorphic hyalinizing angiectatic tumour of soft parts: a case report and review of the literature.

Pleomorphic hyalinizing angiectatic tumour (PHAT) is a recently described, rare, low-grade soft tissue neoplasm. The lesion is characterized by clusters of hyalinized and thrombosed ectatic vessels alternating with a variably cellular stroma composed of atypical cells, many with intranuclear pseudoinclusions. Other features are inflammatory cell infiltration, haemosiderin deposits, focal calcification and minimal to absent mitoses. No metastases have so far been described; however the local recurrence rate has been found to be high. To date, approximately 60 such cases of PHAT and its precursor, "early PHAT", have been described in the world literature. We report the first known case of PHAT from this institution which occurred in the left loin of a 77-year old woman. Three years previously, a smaller lesion excised from the same location had been called an ancient schwannoma on histology. This is the most common differential diagnosis offered for this entity even though the two differ in immunohistochemical profile. 'Early PHAT' was also identified on the periphery of the recurrent lesion.