Multilocular cystic renal neoplasm of low malignant potential

Case contributed by Ammar Ashraf
Diagnosis certain

Presentation

Pain right hypochondrium. No fever, nausea or vomiting.

Patient Data

Age: 40 years
Gender: Male

A small cyst measuring 2.1 x 1.5 cm is seen along the lower medial pole of the right kidney. A few thin septations are appreciable in it. No calcifications, solid component or internal vascularity is noted. Impression: Small right renal cyst with a few thin septations (Bosniak type II).

An exophytic lesion measuring 22 x 18 mm is seen at the lower pole of the right kidney. It has an average density of 27, 37 and 53 HU on plain, arterial and portovenous phase imaging respectively. Two small cysts are seen in the liver (segment 3 & segment 7). Conclusion: Mildly enhancing exophytic cystic lesion at the lower pole of the right kidney (Bosniak type III cyst).

2012 & 2013 FU USs

ultrasound

Small right renal cortical cyst, containing a few thin septations (Bosniak type II), showing no gross interval change when compared with the previous ultrasound examination. 

A well-defined exophytic hypodensity/cystic lesion measuring about 18 x 20 mm is seen at the lower pole of the right kidney. It has an average density of 23, 45 and 52 HU on plain, arterial and portovenous phase imaging respectively. No evidence of local invasion/infiltration is seen. Two small cysts are seen in the liver (segment 3 & segment 7). Impression: Small exophytic right renal cystic lesion (Bosniak type III cyst). No gross interval change is seen in its size when compared with the previous CT scan.

Procedure: Laparoscopic right partial nephrectomy.

Gross Description: Specimen submitted in one container in formalin, labeled as right renal mass.  The specimen comprises perirenal fat and a small cystic mass. The perirenal fat measures 3 x 4 x 2 cm and weighs 15 grams. The small cystic mass measures 1.8 x 1.5 x 1.0 cm. The cystic mass on slicing shows a smooth walled cyst containing clear fluid. On careful inspection, the perirenal fat shows no localized nodularity or other identifiable pathology.  No adrenal gland is grossly identified. 

Histopathological diagnosis: Multilocular cystic renal neoplasm of low malignant potential (previously known as multilocular clear cell renal cell carcinoma). Fuhrman nuclear grade: Grade 1. Renal parenchyma excision margins: Clear. Negative for renal capsular invasion (renal capsule is attenuated but not breached). Renal vascular invasion: Not identified. Negative for perirenal fat invasion.

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