[1075] Cystic Partially Regressed Clear Cell Renal Cell Carcinoma: Clinical and Morphologic Distinction from Multilocular Cystic Renal Cell Carcinoma

Sean R Williamson, Gregory T MacLennan, Antonio Lopez-Beltran, Rodolfo Montironi, Puay Hoon Tan, Guido Martignoni, David J Grignon, John N Eble, Liang Cheng. Indiana University, Indianapolis, IN; Case Western Reserve University, Cleveland, OH; Cordoba University, Cordoba, Spain; Polytechnic University of the Marche Region, Ancona, Italy; Singapore General Hospital, Singapore, Singapore; University of Verona, Verona, Italy

Background: Extensively cystic and sclerotic clear cell renal cell carcinoma (RCC) with only a minor solid component is unusual. Diagnostic terminology for such cases can be ambiguous, leading to confusion with multilocular cystic RCC, which by definition lacks a solid component.
Design: We studied clinicopathologic features in clear cell RCCs with a solid epithelial component that precluded diagnosis of multilocular cystic RCC, yet which had predominant cystic or sclerotic components. We elected to designate these cancers as “cystic partially regressed clear cell renal cell carcinomas”.
Results: Twenty-one tumors were retrieved from patients aged 39 to 74 years (mean 58, male:female 1.6:1). Tumor size ranged from 1.0 to 17.0 cm (mean 4.7) and stage was pT1a (64%), pT1b (21%), pT2a (5%), pT2b (5%) and pT3a (5%). Fuhrman grade was 2 (52%), 1 (34%) or 3 (14%). The solid epithelial component comprised from 5 to 30% of the total tumor (median 10%), while the cystic component comprised 15 to 80% (median 60%) and a sclerotic, hyalinized component comprised 10 to 70% (median 25%). Thin fibrovascular septa lined by clear cells were almost always present (95%); aggregates of clear cells were present within the thin fibrovascular septa in 90% of cases. Broad zones of sclerosis often contained scattered clear cells (86%) and ranged in appearance from a cellular fibroxanthomatous reaction to collagenous and scar-like with a residual network of capillaries. Other features included hemosiderin deposition (76%), calcification (38%), Gamna-Gandy-like nodules (14%) and granulomatous reaction (10%). Two tumors were monitored with imaging prior to resection and showed no change in size over 1 year prior to resection. Long-term follow-up was available for 11 patients, of which none showed aggressive behavior.
Conclusions: Cystic partially regressed clear cell RCC is a unique histologic variant of clear cell RCC, composed of cysts with solid epithelial and sclerotic components that differentiate it from multilocular cystic RCC.
Category: Genitourinary (including renal tumors)

Monday, March 4, 2013 1:00 PM

Poster Session II # 163, Monday Afternoon


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