[Chromophobe renal cell carcinoma: a clinicopathologic study and immunophenotypes of 42 cases].

OBJECTIVE: To study the clinicopathologic features, immunohistochemical profiles and prognosis of chromophobe renal cell carcinoma (ChRCC).

METHODS: Forty-two cases of ChRCC were retrieved from the archival files of the Affiliated Hospital of Qingdao University, 401 Hospital of PLA and Qingdao Municipal Hospital from 2003 to 2011. The clinical and pathologic features of the tumors were reviewed. Hale colloidal iron staining was performed and EnVision immunohistochemistry was used to detect the expression of a series of immunologic markers. Forty cases of clear cell renal cell carcinoma and 10 cases of renal oncocytoma were selected as controls.

RESULTS: The patients included 17 males and 25 females. The age of patients ranged from 39 years to 78 years (median age = 57 years). On gross examination, the tumors ranged from 2 cm to 19 cm in greatest dimension (mean size = 7.3 cm). Histologically, the tumors were mainly composed of solid sheets, acini or tubules of malignant cells. The tumor cells contained clear finely reticular ("chromophobe") and eosinophilic cytoplasm with perinuclear clearing. The nuclear outline was irregular and wrinkled. Nucleoli were inconspicuous and mitotic figures were barely seen. Hale colloidal iron stain was positive in all cases. Immunohistochemically, the tumor cells were variably positive for EMA (100%, 42/42), CK7 (95.2%, 40/42), Ksp-cad (92.9%, 39/42), CK18 (88.1%, 37/42), CD117 (61.9, 26/42), CD10 (31.0%, 13/42) and PAX2 (28.6%, 12/42). They were negative for vimentin, CA IX and TFE3. The follow-up period in 31 patients ranged from 2 to 77 months (average duration = 29 months). Three patients died of tumor metastasis 3, 8, 13 months respectively after the operation. Twenty-eight patients were still alive without evidence of tumor recurrence.

CONCLUSIONS: ChRCC predominantly occurs in middle-aged and elderly patients. It often carries a favorable prognosis. The presence of plant cell-like morphology, pale cells with uniform reticular microvesicular appearance and perinuclear clearing are characteristic histologic features. The diffuse positivity for Hale colloidal iron stain and EMA/CK7/Ksp-cadherin/CD117-positive immunoprofiles are also useful in differential diagnosis.