Sudden onset left lower abdominal and scrotal pain.
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There is a large exophytic mass arising from the upper pole of the right kidney which measures approximately 11 x 10 x 12 cm (trans x AP x CC). A smaller lesion is seen arising from the upper pole of the left kidney measures 5 x 6 x 5 cm.
On the non-contrast study the lesions are relatively isodense to renal parenchyma. Both lesions appear fairly well circumscribed. The lesions do demonstrate contrast enhancement, although the degree of enhancement is less than the adjacent normal renal parenchyma. The large lesion on the right has central hypodensity, compatible with necrosis within the tumour. There is no calcification.
There does not appear to be any tumour extension into the right or left renal veins or the IVC. There is no local invasion into adjacent viscera or muscles. There is no hydronephrosis or obstruction.
The lung bases demonstrate cystic changes which appear paraseptal in location.
Right kidney with proximal ureter surrounded by perinephric fat (23 x 11 x 11 cm, 1140 g). The adrenal gland is also noted sitting on the perinephric fat, gold/yellow in colour. No obvious tumour masses are identified within the adrenal gland. On sectioning the kidney, there is a 11 x 11 x 8 cm orange/yellow well circumscribed tumour in the upper pole. The tumour displays areas of necrosis and foci of haemorrhage. Large 5 cm haematoma within the tumour. The remaining renal parenchyma appears hypertrophied with a dilated pelvicalyceal system and ureter, no other focal lesions.
Left renal core biopsy
Sections show epithelial neoplasm composed of a mixture of clear cells and cells with abundant eosinophilic cytoplasm. Compact crowded nests with large polygonal cells and occasional prominence of cell membranes. Granular eosinophilic cytoplasm is prominent in approximately 70% of cells with no convincing perinuclear halos. The nuclei are rounded without rasinoid forms or binucleation. Immunohistochemistry: PAX-2 positive, cytokeratin 7 positive (but not diffusely strong more suggestive of choromophobic carcinoma); negative RCC markers (vimentin, RCC antigen, CD10. This lesion (similar to the lesion in the right kidney) is difficult to accurately classify as either chromophobe carcinoma or oncocytoma because it shows overlapping morphological and immunohistochemical findings. It is best regarded as a hybrid tumour.
Birt-Hogg-Dubé syndrome is a rare syndrome typified by renal masses (often bilateral), fibrofolliculomas and lung cysts. It is inherited in an autosomal dominant pattern and it has been reported that approximately 12-34% of patients with Birt-Hogg-Dubé will develop renal tumours by the fourth and fifth decades of life.