[Acquired cystic kidney disease-associated renal cell carcinoma: a clinicopathologic study of three cases]

Objective: To study the clinicopathologic, immunohistochemical (IHC), histogenetic and prognostic features of acquired cystic kidney disease-associated renal cell carcinoma (ACKD-RCC). Methods: Three cases of ACKD-RCC, including two from 401 Hospital of PLA and one from the Affiliated Hospital of Qingdao University were studied by clinical, histological and IHC analysis with review of relevant literature. Results: All the three patients were male, ranging from 46 to 78 years old. All patients had history of chronic renal failure; two patients were treated with hemodialysis for 9 years and 11 years, respectively. In two cases the tumor sizes were 2.5 cm and 3.5 cm, respectively, and the tumor border was distinct. The remaining case showed extensive renal hemorrhage with an inconspicuous mass. Microscopically, the tumor cells were arranged in cribriform, microcystic or acinar structures, with variable papillary structure in one case. Hemorrhage of varying degrees was seen in all three cases, and obvious necrosis was noted in two. The tumor cells had deeply eosinophilic cytoplasm, indistinct cell border, round or oval nuclei, and prominent nucleoli (WHO/ISUP grade 3). Mitoses were rare. Abundant oxalate crystals were seen in two cases. The renal mesenchyme of all three cases were atrophic with variable cystic changes of the renal tubules, the lining cells showed atypical hyperplasia. IHC staining showed all tumors were diffusely positive for vimentin, CD10, RCC, CAM5.2, P504s and mitochondria in the cytoplasm, and were variably positive for EMA (2/3), CK7 (1/3), CA9 (1/3) and PAX8 (3/3). All cases were negative for CD117, HMB45, Melan A and TFE3. After 3-14 months follow-up, one patient died from renal failure six months after surgery. The other two patients were alive without tumor recurrence or metastasis. Conclusions: ACKD-RCC is a very rare renal cell carcinoma. The specific cribriform structure, deeply eosinophilic cytoplasm, prominent nucleoli (WHO/ISUP grade 3), and oxalate crystals deposition, associated with the history of ACKD could aid the diagnosis. ACKD-RCC arises from the proximal renal tubule and its histogenesis might be associated with proliferation and malignant change of the atypical epithelial cells of the cystic renal tubules. ACKD-RCC may have a favorable prognosis except for tumors with sarcomatoid differentiation.