Two cases of lung neuroendocrine carcinoma with carcinoid morphology

Abstract

Background The category of grade 3 neuroendocrine tumor (NET G3) was newly introduced in the 2017 World Health Organization (WHO 2017) classification of neuroendocrine neoplasms of the pancreas. Pancreatic NET G3 shows a carcinoid-like morphology with high proliferative activity and the prognosis is intermediate between NET G2 and neuroendocrine carcinoma. There is no category corresponding to NET G3 in the current WHO 2015 classification of lung tumors. Herein, we report two cases of lung neuroendocrine carcinoma with carcinoid morphology that correspond to NET G3. Case presentation Case 1: An abnormal chest shadow was detected in a 78-year-old female never-smoker during a routine medical examination. She was asymptomatic. The radiological assessment revealed a mass in the peripheral S4 segment of the right lung. She underwent right middle lobectomy for the mass preoperatively diagnosed as non-small cell lung carcinoma. Postoperative histological examination revealed a neuroendocrine tumor with carcinoid morphology and a mitotic count of 15/2 mm2. Case 2: An abnormal chest shadow was detected in a 74-year-old female never-smoker undergoing follow-up for another disease. She was asymptomatic. The radiological assessment revealed a mass in the peripheral S3 segment of the right lung. She underwent right upper lobectomy for the mass suspected to be lung carcinoma. Postoperative histological examination revealed a neuroendocrine tumor with carcinoid morphology with mitotic count of 13/2 mm2. Both of these tumors showed carcinoid morphology but with a mitotic count exceeding 10/2 mm2; thus, we diagnosed them as small cell lung carcinomas according to the current WHO 2015 classification. Conclusions Our tumors occurred in female never-smokers and their histology showed carcinoid morphology without extensive necrosis. Moreover, proliferative abilities of them were extremely low compared to small cell lung carcinoma. The clinical and pathological features of our tumors appeared to be different from those of small cell lung carcinoma. Although there is no category corresponding to NET G3 in the current classification of lung tumors, we consider that our tumors may correspond to NET G3 and identification of this subset is relevant for therapeutic management.

The 2021 WHO Classification of Lung Tumors: Impact of Advances Since 2015

“…Carcinoid Tumors With High Proliferation. In recent years, several papers have reported small series of NENs, 143,147,[149][150][151][152][153][154][155] characterized by the welldifferentiated, organoid morphology of carcinoids, but an elevated proliferative activity as documented by a mitotic count exceeding 10 per 2 mm 2 , thus meeting the criteria for a diagnosis of LCNEC rather than carcinoid (Fig. 6A).…”

The Ki-67 antigen in the new 2021 World Health Organization classification of lung neuroendocrine neoplasms

“…In the new 2021 edition of WHO classification on lung tumors, it was recognized that there is an emerging group of primary pulmonary atypical carcinoids with elevated mitotic counts and/or Ki-67 proliferation rates. However, there was insufficient data to define diagnostic criteria for a specific entity and the use of NET G3 was regarded as premature 53 , 67 , 69 , 70 , 74 , 75 . The existence of proliferating carcinoids is likely to be an underrecognized phenomenon in thoracic pathology, with instances documented in the lung 55 , 68 , 75 and the thymus 76 , 77 .…”

Specific Genomic Alterations in High-Grade Pulmonary Neuroendocrine Tumours with Carcinoid Morphology

“…This entity was also observed in a recent large study of stage IV carcinoids, accounting for 27% of the samples [8]. There is still no consensus concerning the name of this entity and the terms "high-grade lung carcinoids," "grade 3 atypical carcinoids," "high-grade lung NET," "lung NET G3," "lung well-differentiated neuroendocrine neoplasms with a Ki-67 > 20%," "lung carcinoid with a Ki-67 > 20%," or "high-grade NEC of the lung with carcinoid morphology" have been discussed [6,[9][10][11]. In the digestive system, a similar subgroup of proliferative well-differentiat-ed NETs was recently recognised in the 2017 WHO classification of pancreatic and 2019 WHO classification of digestive neuroendocrine neoplasms (PanNEN and DigNEN), named well-differentiated neuroendocrine tumours of grade 3 (NET G3).…”