A case of large renal angiomyolipoma resulted in hydronephrosis

Renal angiomyolipoma is one of the members of the perivascular epithelioid cell (PEC) tumour family. It has a characteristic triphasic morphology featuring varying proportions of dysmorphic blood vessels, smooth muscle cells, and mature adipose tissue. Large angiomyolipomas pose a risk of haemorrhagic complications.

A 47-year-old woman presented with right abdominal pain for 2 months, and radiological investigation revealed a 14.2 cm renal mass causing hydronephrosis. The symptoms persisted after arterial embolisation and hence, nephrectomy was performed. The excised renal tumour weighed 1,442 grams. There was a well-circumscribed yellow mass confined within the Gerota's fascia. Histological examination revealed a classic triphasic morphology comprising mature adipose tissue, dysmorphic blood vessels, and smooth muscle. Notably, there were post-embolisation histological changes in extensive fat necrosis and foreign body giant cell reaction. Immunohistochemically, it expressed HMB45, MelanA, and SMA, while it was negative for PAX8 and pan-cytokeratin.

We described a case of renal angiomyolipoma with classic gross appearance of adipose-rich tumour and the triphasic histological features and discussed the post-embolisation histological changes.