Primary small cell neuroendocrine carcinoma combined with squamous carcinoma of the ureter after renal transplantation: a rare case report.

A 47-year-old female presented with a 1-month history of painless gross hematuria after undergoing kidney transplant 4 years. Computed tomography revealed mass-like soft tissue density in the middle-lower portion of the right autologous ureter, which was up to the upper margin of the fourth lumbar vertebra, down to the distal ureter near the entrance of the bladder. The patient underwent right autologous nephroureterectomy resection. Gross examination showed a white, partly yellow mass in the middle-lower portion of ureter. Light microscopy showed a small cell neuroendocrine carcinoma (SCNEC) admixed with squamous carcinoma, invading the ureter wall to periureteric fat tissue, and there was invasion of the lymphatic and renal portal vein. The SCNEC was diffusely positive for CD56 and syn, and squamous carcinoma was positive for P40, P63 and CK5/6. Ureteral SCNEC is a rare malignant tumor with high invasiveness and poor prognosis. Diagnosis mainly depends on pathologic morphology and immunohistochemical markers. Positive neuroendocrine markers are one of the important references for this tumor. Surgical treatment and postoperative radiotherapy and chemotherapy are the main treatments according to cases reported.