Fig. 3.

Histologic features of NECs of the pancreas [H&E stain (a–c), and Ki67 (d–f), respectively]. The left column (a, d) is a case of WDNEC, the middle column (b, e) is of LCNEC, and the right column (c, f) is of SCNEC. Morphology of WDNECs shows a close similarity to that of NET-G1/G2, characterized by monomorphic growth of tumor cells with highly preserved endocrine cell features. Although LCNECs have features of endocrine cells as well, they are distinguished from WDNECs by increased nuclear atypia, cellular pleomorphism, and the frequent presence of tumor necrosis. SCNECs are composed of small cells with dense chromatin, scarce cytoplasm, and remarkable mitotic activity. These are reminiscent of small cell carcinomas of the lung