Xp11.2/TFE3 translocation-associated renal cell carcinoma with multilocular cystic structures in an elderly patient: a case report

Background: Xp11.2 translocation-associated renal cell carcinomas (Xp11.2-RCCs) are a rare subtype of renal neoplasm. The incidence of these tumors is lower in the elderly than in children and young adults. Furthermore, there have been very few reports of Xp11.2-RCCs with multilocular cystic structures. Case: A 66-yearold Japanese female was admitted to our hospital with amultilocular cystic lesion in her right kidney. Computed tomography revealed that the lesion occupied the cortex and medulla of the upper pole of the right kidney, and partial nephrectomy was performed. Resected tissue contained a multilocular cystic tumor measuring 4.5×4.3×4.0 cm. Histologically, the cyst walls were composed of thin fibrous septa covered by a few layers of tumor cells with a clear cytoplasm. Psammoma bodies were scattered in the cyst lining. Immunohistochemically, most of tumor cells were positive for TFE3, α-methylacyl CoA racemase (AMCAR), and cathepsin K. Tumor cells also showed immunoreactivities for CD10 and cytokeratins, but were negative for carbonic anhydrase 9 and c-kit. Fluorescence in situ hybridization using a break-apart probe revealed monoalleleic TFE3 breakage. Based on these results, the tumor was diagnosed as Xp11.2-RCC, even though the patient’s age and morphological architecture were not representative. Conclusion: This case demonstrated that Xp11.2-RCCs may occur in adults with multilocular cystic structures. Retrospectively, the recognition of psammoma bodies represented an important diagnostic sign.