Introduction
Renal oncocytomas, characterized by the proliferation of oncocytes within the renal parenchyma, are typically benign tumors. Renal Oncocytomas are relatively uncommon and are usually of small size (average size 4.9 ± 2.7 cm). Cases of exceptionally large renal oncocytomas are very rare which presents a unique set of challenges in diagnosis and clinical management. Understanding and addressing these cases is of paramount importance due to the potential impact on patient outcomes and the intricate balance between diagnostic accuracy and therapeutic intervention.1, 2, 3, 4, 5
Case Presentation
A 37-year-old male patient presented with anorexia, weight loss (5kg in 1 month), generalized weakness, abdominal lump. On examination Large palpable mass occupying almost whole abdomen with firm to hard in consistency. On laboratory investigations Hemoglobin – 6.8gm%, TC – 5420 /cu.mm, Serum Creatinine – 1.02mg/dl, Serum Calcium – 1.07mmol/L. On USG abdomen there was a large irregular heterogeneous mixed solid cystic lesion noted along upper pole of left kidney which measures 199 x 142mm. On CT abdomen a large smoothly marinated, heterogeneously enhancing soft tissue density lesion is seen at upper pole of left kidney. Scattered foci of calcifications are seen within the lesion. It measures 253mm x 202mm x 185mm.After anemia correction patient underwent left open radical nephrectomy. On gross examination Weight: 5380 gm. 29.0 x 21.0 x 13.5 cm sized left kidney with perinephric fat received. On cut open there is a presence of huge mass measuring 27.0 x 19.0 x 11.5 cm sized with only 6.0 cm sized normal kidney identified at the periphery of mass. Mass is single, solid and cystic, yellowish and brownish black in color with areas of hemorrhage and necrosis. On microscopy, Sections from mass show cells with abundant acidophilic granular cytoplasm growing in nesting and alveolar pattern and at places in tubular fashion. The nuclei are small, round and regular. Focal loose fibrous and hyalinized stroma present. There are presence of areas with hemorrhage, severe necrosis and infiltration by inflammatory cells neutrophils, lymphocytes and plasma cells. Sections from perinephric fat, ureter and renal vessels are free from tumor cells. On immunohistochemistry, CK 7: negative, CD 10: focal positive, CD 117: weakly positive. So Renal Oncocytoma was diagnosed.
Discussion
According to English literature largest and heaviest Renal Oncocytoma reported is 4652 gm and the case we report is having weight of 5380 gm, is a largest Renal oncocytomas till now reported as per our knowledge. Renal oncocytomas make up approximately 7% of all primary non urothelial epithelial renal neoplasm. Typical gross features of renal oncocytoma is a tan or mahogany brown colored cut surface generally similar to normal renal parenchyma, stellate scar may be present. Microscopically, oncocytoma shows cells having abundant acidophilic granular cytoplasm, growing in nesting and tubular fashion. The nuclei are usually small, round and regular. From nuclear feature also we can differentiate oncocytoma from chromophobe renal cell carcinoma as chromophobe renal cell carcinoma has resinoid nucleus, having irregular nuclear border and perinuclear clearing. In a huge renal oncocytoma gross as well as microscopic finding differs. It may have solid and cystic areas and necrosis due to lack of blood supply in the centre of tumor. 6, 7, 8, 9, 10
Conclusion
Huge renal oncocytoma more than 5kg is very rare. Very few huge renal oncocytomas are reported in literature. Renal oncocytoma can present as solid and cystic morphology with areas of necrosis. Histology findings and immunohistochemistry confirms the diagnosis in unusual type of gross appearance. Instead of Huge size of tumor, perinephric fat may be free from tumor cells which suggest better prognosis for patient.
