Myxolipoma of the renal capsule: A case report

Although lipomas are the most common mesenchymal tumors of the human body, primary intrarenal lipomas are quite rare. In this report we present a case of benign mesenchymal tumor with lipomatous and myxoid components.

A sixty one years old male patient was admitted to our outpatient clinic for a general control since he had a right radical nephrectomy operation due to renal cell carcinoma (RCC) eight years ago and he did not have any urological control for last 3 years. However the urinary ultrasound revealed a mass lesion on left kidney and then on axial contrast-enhanced computed tomography (CT) scan, there were two masses on the left kidney. In the magnetic resonance imaging (MRI), the tumor on cortex was depicted as a homogeneous low-signal intensity on the T1-weighted pulse sequence and as a heterogeneous high-signal intensity on the T2-weighted pulse sequence. In pathological evaluation, the biopsy material of the cortical mass was a tumoral lesion containing lipomatous and mixoid areas without atypia, mitosis or necrosis which was diagnosed as myxolipoma.

Myxolipoma, an uncommon type of lipoma, is a benign tumor composed mainly of fat cells with myxoid (mucus-like) components. In our case, the tumor was composed of mature adipocytes together with areas rich in mucoid substances and there were no malignant features including lipoblasts, mitosis or abundant capillary network.

Herein we present a case of a fatty tumor originating from the renal capsule with the histologic diagnosis of myxolipoma. To the best of our knowledge, myxolipoma, a very rare form of lipoma, is not reported in kidney, in the literature before.