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Table 1 1999 WHO criteria for diagnosis of NE tumors

From: Genetic and Molecular Coordinates of Neuroendocrine Lung Tumors, with Emphasis on Small-cell Lung Carcinomas

Histologic Type Criteria
Typical carcinoid Carcinoid morphology, ≥0.5 cm, <2 mitoses/2 mm2 (10 HPFs), without necrosis
Atypical carcinoid Carcinoid morphology, 2–10 mitoses/2 mm2 (10 HPFs), and/or necrosis
Large-cell NE carcinoma NE morphology (organoid nesting, palisading, rosettes, trabeculae), ≥10 mitoses/2 mm2 (10 HPFs), large zones of necrosis, cytologic characteristics of a NSCLC, positive immunohisto-chemical staining for one or more NE markers, and/or NE granules by electron microscopy
Small-cell carcinoma Small size and specific cytologic characteristics, ≥11 mitoses/2 mm2 (10 HPFs), large zones of necrosis
  1. Abbreviations: HPF, high power fields; NE, neuroendocrine.