Metastatic small cell neuroendocrine carcinoma of the pelvic floor

Abstract

A 80-year-old woman with history of cervical carcinoma (treated with hysterectomy and radiotherapy 44 years ago) and urothelial carcinoma of the bladder (treated with cystectomy 2 years ago) underwent fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (F-FDG-PET/CT) for oncologic follow-up. F-FDG-PET/CT showed an area of increased radiopharmaceutical uptake corresponding to a 5 cm mass in the left pelvic floor and multiple hypermetabolic areas in the skeleton without significant abnormalities at the co-registered CT (Fig. 1a–e). These findings were suspicious for relapse of urinary bladder carcinoma. Due to the increased chromogranin-A serum levels (800 U/L), the patient underwent somatostatin receptor scintigraphy with Indium111-pentetreotide (In-SRS) in the suspicion of a neuroendocrine tumor. In-SRS revealed multiple areas of increased radiopharmaceutical uptake corresponding to the F-FDG-PET/CT findings in the pelvic floor and the skeleton, suggesting their neuroendocrine origin. Based on these imaging findings, the patient underwent biopsy of the pelvic mass. Histology was suggestive for a small cell neuroendocrine carcinoma (SCNEC) (Fig. 1f–h). The final diagnosis based on pathology and imaging findings was SCNEC of the pelvic floor with bone metastases; thus, the patient was addressed to chemotherapy. SCNEC is a very aggressive neoplasm usually arising from the lung, but the primary site may be rarely and virtually located in any organ [1]. In particular, to date, no cases of SCNEC arising from the pelvic floor are described in the literature. We could hypothesize that the neuroendocrine carcinoma described in our case may be derived from neuroendocrine cells in the peritoneum. Little has been published regarding the imaging features and metastatic patterns of extrapulmonary SCNEC [2]. Previous reports demonstrated that F-FDG-PET/CT could provide relevant information in patients with extrapulmonary SCNEC located in different anatomical sites, including the pelvic organs [3]. In our case, F-FDG-PET/ CT has been very useful in detecting and staging this extremely rare extrapulmonary SCNEC mimicking a relapse of urinary bladder carcinoma.