Typical carcinoid
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Carcinoid morphology, ≥0.5 cm, <2 mitoses/2 mm2 (10 HPFs), without necrosis
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Atypical carcinoid
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Carcinoid morphology, 2–10 mitoses/2 mm2 (10 HPFs), and/or necrosis
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Large-cell NE carcinoma
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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
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Small-cell carcinoma
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Small size and specific cytologic characteristics, ≥11 mitoses/2 mm2 (10 HPFs), large zones of necrosis
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