of a 27-year-old man with a 38 cm primary retroperitoneal teratoma (RT) with well differentiated NET and presence of erectile-type tissue.
CASE REPORTA 27-year-old male presented with COVID-19 related symptoms. Chest imaging obtained during work up revealed a retroperitoneal mass. He reported an increase in abdominal girth, but denied pain, gastrointestinal symptoms, or weight change. Past medical history and family history were unremarkable. On exam, he had a large, firm, palpable left sided abdominal mass. Scrotal exam was unremarkable with no palpable testicular masses. Preoperative tumor markers were not obtained. On CT, the mass was 30 cm in greatest dimension with solid and cystic areas, and located in the retroperitoneum, anterior to the left kidney and displacing the left ureter anteriorly.(Figure 1). The tumor was believed to be a sarcoma prior to resection.The patient subsequently underwent an open, transperitoneal excision of the retroperitoneal tumor. A midline incision extending from his xiphoid to his pubis was utilized. Despite the tumor's proximity to the spleen and inferior mesenteric artery, all structures were able to be dissected free and spared. With the help of a ureteral stent, the left ureter was identified anterior to the mass and was also dissected free without injury. Parasitic vessels arose directly from the aorta and implanted into the medial tumor. These were effectively ligated with bipolar diathermy (Figure 2). Recovery was uneventful and he was discharged on postoperative day 3.Gross examination of the excised tumor revealed a multilocular solid and cystic mass, 38 cm in largest dimension, primarily comprised of yellow adipose tissue with cystic areas containing thick, yellow grumous brown-tan keratinous material. Hair, bone, and cartilage were also identified. Histologic examination revealed tissue derived from all three germ layers with epidermal (squamous and columnar epithelium lined cysts), mesodermal (adipose, cartilage, bone, and fibrous tissue), and endodermal elements (gut epithelium). There was notably vascular tissue resembling erectile tissue identified. Two foci incidentally identified on histology were comprised of well-differentiated neuroendocrine cells that showed diffuse immunocytochemical expression of synaptophysin, chromogranin, SATB2, and CDX2 without pancreatic polypeptide, glucagon, or somatostatin, a pattern of staining resembling NET of distal small bowel/appendiceal NET. The Ki-67 proliferation index demonstrated nuclear staining in 2% of cells (Figure 3). There was no gross or histologic evidence of a background supernumerary testis. These findings along with the imaging findings are consistent with well differentiated enterochromaffin cell NET, grade 1 arising in a primary retroperitoneal mature cystic teratoma.Postoperative tumor markers were within normal limits (alpha fetoprotein [AFP], betahuman chorionic gonadotropin [bhcg]). Post-operative scrotal ultrasound was negative. Plasma 5-HIAA was obtained due to NET finding and within normal limits. Tum...