Ann. Coll. Surg. H.K. (2000) 4, 167–168 Case report Collecting duct carcinoma presenting as a bleeding complicated renal cyst Man-Chiu Cheung ( ), 1 * Siu-Hung Lo ( ), 1 Ui-Soon Khoo ( ) 2 and Po-Chor Tam ( ) 1 1 Division of Urology, Department of Surgery and 2 Department of Pathology, University of Hong Kong Medical Centre, Hong Kong SAR. Collecting duct carcinoma is a rare type of renal cell carcinoma. It is usually diagnosed pathologically and carries a poor prognosis. Renal cell carcinoma arising within a cyst is also rare. We report a case of collect- ing duct carcinoma presenting as a giant, bleeding complicated renal cyst with minimal solid component. The patient had a relatively long survival after nephrectomy. pain and a large abdominal mass. On physical ex- amination, she was pale and a ballotable mass filling the left lumbar area was detected. Ultrasonography and abdominal computerized tomography revealed a giant cystic mass measuring 17 cm ¥ 11 cm at the lower pole of left kidney with some intramural irregu- larity (Fig. 1). Apart from microcytic hypochromic anaemia (haemoglobin, 8 g/dL), the patient’s urin- alysis and blood biochemistry were normal. Urine for cytology was negative. In view of the symptoms, exploration of the kidney was performed. Intraopera- tively, the giant renal cyst was found to be adherent to the tail of pancreas and left ureter, and was displac- ing the rest of the kidney anteriorly and upwards. When the cyst was aspirated, the fluid was found to be haemorrhagic and continuous bleeding into the cyst was noted. Therefore, a left nephrectomy was performed. Macroscopically, the renal cyst was centrally located near renal pelvis and almost entirely cystic. It had tan-coloured irregular interior lining covered with sponge-like material. The tumour was well circum- scribed without gross extension to perinephric fat. There was neither renal vein nor regional lymph node involvement. Microscopic examination showed that the wall was lined with papillary adenocarcinoma composed of fibrovascular stalks and fronds (Fig. 2). Intracellular mucin and glycogen was absent. The tumour cells stained positive for high molecular weight *Author to whom all correspondence should be addressed. Email: mccheunguro@aol.com Received 3 January 2000; accepted 29 March 2000. Introduction Collecting duct carcinoma is a rare type of renal cell carcinoma (RCC). It is believed to arise from the col- lecting tubules, rather than the proximal convoluted tubules where the usual type of RCC arises. This pos- sibility was first recognized by Mancilla-Jimenez et al. in 1976. 1 To our knowledge, less than 40 confirmed cases have been reported in the English medical literature. Collecting duct carcinoma usually presents as haematuria or an abdominal mass and affects a younger age group. It always arises as a renal mass near the inner medulla with extension into the cortex or hilar tissue, leading to distortion of pelvicalyceal system. Renal cell carcinoma arising within a solitary or multiloculated cyst is rare; 2 however, a renal cyst close to a collecting duct carcinoma has been reported. 3 We believe that our patient is the first reported case of collecting duct carcinoma present- ing in the form of a bleeding, giant complicated renal cyst alone with a minimal solid component. Case report A 46-year-old woman was referred to University of Hong Kong Medical Centre, Hong Kong, with left loin Key words: collecting duct carcinoma, renal cyst, renal tumour.