Discussion:

Urinary bladder Xanthoma is a very rare, non-neoplastic, tumor-like lesion.

It occurs due to reactive proliferation of lipid laden macrophages.

Usually seen in patients with altered lipid metabolism in conditions like essential hyperlipidemia, primary biliary cirrhosis, diabetes mellitus etc. They can also occur secondary to local surgeries, trauma or inflammation.

Patients are usually asymptomatic or can present with symptoms like gross hematuria and lower abdominal pain.

 

Grossly, it appears as yellow flat lesion with ill defined borders.

Microscopically, xanthomas typically represent collections of lamina propria macrophages, without an associated inflammatory component or multinucleated giant cells. These histiocytic collections need to be distinguished from the benign foamy appearing urothelial cells, typically seen superficially in the normal urothelium or in the superficial urothelial layers of urothelial neoplasms (e.g. urothelial papilloma).

Bladder xanthomas also need to be distinguished from xanthogranulomatous cystitis, malakoplakia, granular cell tumour and signet‐ring cell carcinoma.

The histiocytes in malakoplakia show small basophilic extracellular or intracytoplasmic calcospherules called Michaelis-Gutmann bodies that stain positive for von Kossa stain, iron and PAS. These structures are absent in xanthoma.

In xanthogranulomatous touton-type multinucleated giant cells, plasma cells and lymphocytes are seen in addition to xanthoma cells.

Granular cell tumors can stain positive for CD 68 and S100 whereas xanthomas are CD 99 positive and S100 negative. Also, in granular cell tumor cells have eosinophilic or grey granular abundant cytoplasm and poorly defined cell borders.

Signet ring cell carcinoma has ovoid cells and peripheral crescentic hyperchromatic nucleus with infiltration into adjacent layers.

Complete surgical resection of the lesion is the main treatment.