Primary carcinoid tumor of the kidney with estrogen and progesterone receptor expression.

Primary carcinoid tumors are uncommon neoplasms in the kidney. The current study presents a case of primary carcinoid tumor of the kidney in a 49-year-old female who suffered from painless gross hematuria for half a month. Left hydronephrosis, a horseshoe kidney and a space-occupying lesion of the left ureter were found by abdominal computed tomography scans and ultrasonic testing. Surgery was performed and an oval tumor was found under the left ureter; the tumor and left kidney were excised completely. The neoplasm was composed of solid nests of cells, trabeculae, adenoid structures and anastomosing cords in a loose and myxoid background. The tumor cells, which were consistent in volume, exhibited centrally oval nuclei with inconspicuous nucleoli, and eosinophilic finely granular cytoplasm. Upon immunohistochemical staining, the neoplastic cells were positive for AE1/AE3, vimentin, synaptophysin, chromogranin A, estrogen receptor and progesterone receptor, while being negative for epithelial membrane antigen, inhibin A, cluster of differentiation (CD)99, S-100 and CD10. Based on the histological characteristics, a diagnosis of primary carcinoid tumor of the left kidney was formed. The patient did not receive further treatment. The total follow-up period was 18 months after the surgery and repeated imaging examinations every 6 months revealed no recurrence.