Clinicopathological Spectrum of Primary and Metastatic Neuroendocrine Neoplasms

Introduction Neuroendocrine neoplasms (NENs) are a heterogeneous group of tumors with histological features varying from well-differentiated neuroendocrine tumors (WDNETs) to poorly differentiated neuroendocrine carcinomas (PDNECs). In this study, we investigated the clinicomorphological spectrum of NENs including tumor grade, site of origin, and metastasis. Methods We retrospectively studied 125 cases of NENs (at the Department of Histopathology, Liaquat National Hospital and Medical College, Karachi) between the years 2014 and 2020. Slides of these cases were retrieved from the departmental archives and were evaluated for the tumor type, grade, and site of origin. Results The mean age of the patients was 51.25±16.10 years. Overall, the liver was the most common site of the tumor (27.2%), followed by the small bowel (15.2%). Grade 2 was the most common tumor grade (40.8%), and most of the tumors were primary (68.8%). A total of 84.8% of the tumors were WDNETs/carcinoids, while 15.2% were PDNEC. The small bowel was the most common site of primary NENs, followed by the stomach and lung. Among primary neuroendocrine tumors, patients with PDNEC were significantly noted to have a higher mean age than WDNET/carcinoid. Similarly, PDNEC had a higher ki67 index than WDNET/carcinoid. For metastatic NENs, the liver was the most common site of metastasis (71.8%) with the GI/pancreatobiliary tract being the most common primary site of origin (51.3%). Tumors with primary lung origin were found to have a higher tumor grade than primary GI/pancreatobiliary tract origin NENs (p<0.0001). Conclusion In this study, we found that the small intestine and liver were the most common sites for primary and metastatic NENs, respectively. Moreover, primary PDNECs were associated with a higher mean age than WDNETs. Alternatively, metastatic NENs with primary lung origin had a higher tumor grade than primary GI/pancreatobiliary tract origin.