[Clinicopathological features and differential diagnosis of eosionphilic chromophobe renal cell carcinoma]

Objective: To investigate the clinicopathological characteristics of eosionphilic Chromophobe renal cell carcinoma (eChRCC), and differences in morphology, immunophenotype and clinical prognosis betweeneChRCC, renal oncocytoma(RO) and classic Chromophobe renal cell carcinoma (cChRCC). Methods: The clinicopathologic data of 17 patients diagnosed as eChRCC from the Affiliated Hospital of Qingdao University (13 cases) and 971 Hospital of PLA Navy (4 cases) from October 2006 to February 2019 were collected. Immunohistochemical analysis was carried out to compare the immunophenotypes between 17 cases with ChRCC, 27 cases with RO and 30 cases with cChRCC. Resuls: Among the 17 patients, seven were males and ten were females, and the age ranged from 40 to 75 years (median 54 years). Clinically, 15 cases of 17 were found accidentally by physical examination. The tumor size ranged from 1.8 cm to 10.0 cm (average 5.7 cm) and the cut surface of 15 cases were solid, one case was solicl and cystic, and one was cystic. Most showed gray to red, and partially soft, gray to yellow appearances. Microscopically, most tumors presented solid growth pattern with vary number of alveolar structures (12 cases). Some were predominately characterized by cystic structure (3 cases), alveolar structure(1 case) and microcapsule structure (1 case). There were boundaries with varying degrees of clarity between tumor cells in 16 cases. The cytoplasm of tumor cells was eosinophilic and the nuclei were small round or irregular with focal perinuclear haloes in 14 cases. Large polygonal cells with light-stained cytoplasm appeared focally in 9 cases, and edematous areas with scarce tumor cells were found in 4 cases. Among 7 cases, 4 cases focally invaded peripheral renal parenchyma, 2 cases invaded adipose tissues outside the renal capsule, and 1 case presented invasion of renal sinus. Immunohistochemically, all cases were moderate to strong positive for EMA and claudin-7. CK7, CD117 and Ksp-cad were highly expressed with the expression rates of 12/17, 15/17, 14/17, respectively. Cyclin D1, AMACR, CD10, S100A1, and RCC were rarely expressed with the expression rates of 4/17, 3/17, 4/17, 1/17 and 1/17, respectively. On the contrary, all cases were negative for vimentin, CAⅨ, HMB45 and Melan A. The Ki-67 proliferation index of the 17 cases was 1%‒5%. Follow-up data were available for all 17 patients from 7 to 154 months. Among them, 15 patients were alive without tumor recurrence or metastasis, one patient died of pulmonary metastasis after 31 months of surgery and one patient died of hepatic metastasis after 38 months of surgery. Conclusion: eChRCC has overlapping morphology and immunophenotype with RO. eChRCC is characterized by solid nest or alveolar structure, distinct border between tumor cells, perinuclear halos and lacking of interstitial looseness and edema. Scattered large polygonal cells with light-stained cytoplasm in tumor tissue play a significant role in the diagnosis of eChRCC. The positive expression of CK7, CD117, claudin-7 and Ksp-cad, and negative expression of cyclin D1, S100A1 are helpful to the diagnosis and differential diagnosis of eChRCC. The prognosis of eChRCC after complete surgical resection is excellent and few cases may have long-term metastasis. There is no significant difference in prognosis between eChRCC and cChRCC, but eChRCC shows better outcome than RO.