Small cell neuroendocrine carcinoma of the bladder with synchronous Warthin's tumor of the parotid gland: A rare case and overview of the literature

Introduction. Neuroendocrine tumors (NETs) develop from the epithelium rich in enterochromaffin cells. NETs most commonly originate from the gastrointestinal and respiratory tract. NETs rarely occur in the urinary bladder. Synchronous tumor is defined as having two different tumors growing at the same time in an organ. NETs are frequently associated with synchronous or metachronous second-primary malignancies. In this paper, we describe a synchronous tumor: a small cell neuroendocrine carcinoma (SCNEC) of the bladder and a Warthin's tumor (WT) of the parotid gland, both of which are highly rare in the literature. Case report. A 79-year-old male patient was admitted to the hospital with gross hematuria and nodular mass involving the wall of the urinary bladder. The bladder neck resection and transurethral bladder resection (TURB) were performed. The tumor consisted of small, uniform, round, and spindled-shaped cells with chromatin dark nuclei and numerous mitotic figures. The cells were immunoreactive for CD56, synaptophysin (diffuse), and keratin (focal). The diagnosis of SCNEC with focal urothelial carcinoma in situ component was established. PET-CT was performed for staging purposes, and it showed a residual/recurrent tumor behind the lumen of the bladder floor and two nodular lesions with metabolic activity in the left parotid. After the biopsy of the parotid gland, it was diagnosed as WT. No metastasis of SCNEC was found at the time of diagnosis, and the patient received four cycles of induction chemotherapy (Etoposide combined with carboplatin chemotherapy) followed by chemoradiotherapy. Conclusion. In this case report, an extremely rare case of primary SCNEC of the bladder with synchronous of the parotid gland is presented, along with a discussion on the clinical presentation, immunohistochemical and cytomorphological characteristics, management, biological behavior, and prognosis.