Neuroendocrine Tumors

Carcinoid tumor

Tumors have:

  • Ribbon or sheet architecture
  • Polygonal cells
  • Moderate cytoplasm
  • Regular nuclei
  • Finely stippled chromatin
  • Small nucleoli
  • Delicate capillary stroma
  • <2 mitoses/10 HPF
  • Chromogranin +

Tumorlet = minute carcinoid < 0.5 cm diameter in lung periphery

Neurosecretory granules

By EM, many dense-cored, membrane-bound granules are found in the cytoplasm (arrows).

Atypical carcinoid tumor (well-differentiated neuroendocrine carcinoma)

Tumors have:

  • Ribbon or sheet architecture
  • Nuclei resemble carcinoid tumors but show hyperchromatism, some irregularity in shape
  • Moderate cytoplasm
  • Focal necrosis (left)
  • 2-10 mitoses/HPF

Prognosis is intermediate between carcinoid tumors and small cell tumors.

See also Case 7 and Case 13

Small cell carcinoma

Tumors have:

  • Sheets of cells
  • Cells with scant cytoplasm
  • Molded nuclei
  • Uniform fine chromatin,
  • "Absent" nucleoli
  • >10 mitoses/10 HPF
  • Necrosis (not shown)
  • Few dense-cored granules by EM

See also Case 23

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