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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