Pleomorphic Hyalinizing Angiectatic Tumour (PHAT) of soft parts
Clinical History
The patient has a 10 year history of a mass on the dorsum of his left foot. Over the past year, the mass has been rapidly growing in size. He has had no pain and it causes no functional limitations.
Case Discussion
Pleomorphic Hyalinizing Angiectatic Tumour of Soft Parts (aka PHAT) is a rare, locally aggressive but non-metastasizing mesenchymal neoplasm. It typically presents in adults and in the subcutaneous tissue of the lower extremities, particularly the ankle and foot. Microscopically, the tumour is composed of multiple clusters of thin-walled ectatic vessels embedded in a spindled stroma. The tumour cells are spindled to pleomorphic and may contain intranuclear inclusions. There is a variable inflammatory infiltrate. Mitoses are rare and necrosis is typically absent. A unique finding is the lining of vessels with fibrin which leaks into the stroma creating large areas of hyalinization.
The slide shown highlights the vascular component.
Forse, C., Chang, M. Soft tissue, pleomorphic hyalizing angiectatic tumour of soft parts. Digital Laboratory Medicine Library, Dept of Laboratory Medicine & Pathobiology, University of Toronto. Published
. Accessed December 17, 2025. https://dev.dlml.cflabs.ca/image/soft-tissue-pleomorphic-hyalizing-angiectatic-tumour-soft-parts-lmp39546
