Histologic changes: These photos taken from other cases depict additional changes typical of small cell carcinomas.

Azzopardi phenomenon: In necrotic areas of tumor, dark blue DNA liberated from dead cells sometimes coats vessel walls (arrow). The tumor cells surrounding the vessels show coagulative necrosis. The pink area at the lower right shows karyolysis of tumor nuclei.

Vascular invasion of tumor: The rounded nests of tumor with central necrosis (arrow) lie in a distended vein. Such tumor may be disseminated systemically.

Spindled cells: Here, tumor cells show elongation or spindling of nuclei, a common feature of all types of neuroendocrine tumor from tumorlet to small cell carcinoma. The small, dark nuclei represent dying tumor cells, mitotic figures, or lymphocytes.

Clinical summary Image 5

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