What are the histologic patterns of carcinoid tumors?

Updated: Feb 12, 2019
  • Author: Cameron K Tebbi, MD; Chief Editor: Max J Coppes, MD, PhD, MBA  more...
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Upon histologic examination, carcinoid tumors have 5 distinctive patterns: (1) solid, nodular, and insular cords; (2) trabecular or ribbons with anastomosing features; (3) tubules and glands or rosettelike patterns; (4) poorly differentiated or atypical patterns; and (5) mixed patterns. A combination of these patterns is often observed. Tubules can contain mucinous secretions, and individual tumor cells can contain mucin-positive material, which includes the various acidic and neutral intestinal mucin. Tumors rarely have eosinophilic stroma. Capillaries are often prominent. Cells are uniformly round or polygonal with a central nucleus and punctate chromatin as well as small nucleoli and infrequent mitosis. The cytoplasm can be slightly acidophilic, basophilic, or amphophilic. Eosinophilic granules may be present. Immunohistochemically, these tumors have a strong positive reaction to keratin and neuroendocrine markers. These include chromogranin and synaptophysin.

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