Pleomorphic hyalinising angiectatic tumour: Report of a rare case

ABSTRACT Soft tissue tumours are a heterogeneous group, including a few characterised by low malignant potential. The pleomorphic hyalinising angiectatic tumour (PHAT) is one such entity, which is slow growing and non-metastasising. The origin of this tumour is uncertain and has several clinical and morphological mimics. We present the case of a 65-year-old male, who was diagnosed with urothelial carcinoma, and he underwent radical cystectomy with an ileal conduit, after neoadjuvant chemotherapy. Pre-operative ultrasonography of the abdomen also showed a pedunculated soft-tissue lesion in the lower abdominal wall in the subcutaneous plane, which was excised. The histopathological examination of the excised swelling showed features of a rare soft-tissue neoplasm, i.e. PHAT. PHAT is a neoplasm primarily of adults, occurring mostly over the lower extremities. Grossly, they are circumscribed, solid firm masses with blood-filled cystic spaces. Microscopically, typical PHAT is characterised by sheet-like proliferation of the spindle or pleomorphic cells, thin-walled hyalinised ectatic and small vessels and haemosiderin laden in a myxoid extracellular matrix. They often express vimentin and CD34 and may be positive for CD99 and vascular endothelial growth factor. The absence of aneuploidy in PHAT indicates a non-malignancy. However, it is considered to be an intermediate category because of its aggressive behaviour warranting surgical excision with wide margins as treatment of choice. Awareness of the classical morphological features can prevent an erroneous diagnosis of malignancy.