[Eosinophilic solid and cystic renal cell carcinoma: a clinicopathological analysis of four cases]

Objective: To study the clinicopathological characteristics and prognosis of eosinophilic solid and cystic renal cell carcinoma (ESC RCC). Methods: The clinical pathologic data of 4 cases of ESC RCC diagnosed and treated from 2017 to 2019 at the Second Hospital of Longyan City, the Second Affiliated Hospital of Fujian Medical University, and the Zhangzhou Municipal Hospital were collected. The expression of different antibodies was detected by immunohistochemistry, and the diagnosis and differentiate diagnosis were investigated. Results: The 4 ESC RCC cases included 2 males and 2 females, the average age of these patients was 40 years, ranged from 31 to 51 years. The tumors were composed of solid area mixed with giant vesicles and microcapsules of varying sizes. The cyst cavity was lined by neoplastic cells with voluminous eosinophilic cytoplasm and hobnail arrangement. The solid area appeared as diffuse flaky, dense acinar or nested arrangement, the local area was island-shaped and tubular, mixed with a small amount of histiocytes and lymphocytes. Neoplastic cells contained voluminous eosinophilic cytoplasm with obvious fine or coarse particles, eosinophilic globules in part of the cytoplasm, and intracytoplasmic vacuoles in some areas. Immunohistochemical results showed that tumor cells were CK20 expressed (3/3, 2 cases were sparsely positive and 1 case was patched strongly positive), Vimentin (4/4) and CD10 (4/4) sparsely positive, while Actin, HMB45, Melan-A, CD117 and CK7 were negative in all cases. Ki-67 proliferation index was about 1%. Two cases were followed up and the progression free survival were 18 and 24 months, respectively. Conclusions: ESC RCC has unique histomorphological manifestations, CK20(+ ) and CK7(-) are helpful for its diagnosis, and it has common molecular karyotype changes, supporting it as a unique tumor entity. The overall prognosis of the patient is good.