Introduction: Pulmonary neuroendocrine tumors (pNETs) are difficult to classify. We performed a population-based analysis to investigate the application of pNET nomenclature in daily pathology practice.
Methods: Conclusions from pathology reports (2003-2012) describing carcinoids, (large cell) neuroendocrine carcinomas (NECs), and carcinomas with neuroendocrine features/differentiation were retrieved from the Dutch Pathology Registry by queries on location and diagnosis and screened for terminology. Cases with a nonpulmonary or unknown origin and small cell lung cancer were excluded. Diagnoses were clustered into subgroups and the retrieved terminology was compared with the 2015 World Health Organization (WHO) diagnoses. By means of an online questionnaire, interpretation of the non-WHO nomenclature retrieved from pathology reports was evaluated (by 35 physicians and 19 pathologists).
Results: A total of 3216 unique pathology report conclusions with 55 different pNET diagnoses (n = 3052) and 20 uncertain diagnoses (n = 164) were analyzed. Non-WHO nomenclature was used in 15% of diagnoses (n = 488). Diagnoses could be clustered into carcinoids (n = 1086), NEC (n = 1316), carcinomas with neuroendocrine features/differentiation (n = 624), and unspecified pNETs (n = 26). Non-WHO nomenclature within these clusters was found for 7% of carcinoids, 20% of NECs, 13% of carcinomas with neuroendocrine features/differentiation, and 100% of unspecified pNETs and was observed more often in conclusions regarding biopsy or cytological specimens (62% and 12%) compared with resection specimens (26%). Analysis of the questionnaire results revealed that 4 of 19 diagnoses based on non-WHO nomenclature were uniformly interpreted (>50% agreement) by physicians, as were 10 of 19 diagnoses by pathologists.
Conclusions: In 15% of pNETs other than small cell lung cancer, a non-WHO nomenclature diagnosis was provided, more frequently on the basis of smaller specimens. The interpretation was different between physicians and pathologists. Application of uniform nomenclature among all clinicians is advocated.

Carcinoids, Diagnosis, LCNEC, Nomenclature, Pulmonary neuroendocrine tumors,
Journal of Thoracic Oncology
Department of Pathology

Derks, J.L, van Suylen, R-J, Thunnissen, E, den Bakker, M.A, Smit, E.F, Groen, H.J.M, … Dingemans, A.M.C. (2016). A population-based analysis of application of WHO nomenclature in pathology reports of pulmonary neuroendocrine tumors. Journal of Thoracic Oncology, 11(4), 593–602. doi:10.1016/j.jtho.2015.12.106