– Well-differentiated Neuroendocrine Tumor, WHO Grade 1

– Well-differentiated Neuroendocrine Tumor, WHO Grade 2

– Well-differentiated Neuroendocrine Tumor, WHO Grade 3

COMMENT: Histologic sections of the *** biopsy show a proliferation of nests of cells with round nuclei and stippled chromatin. These cells show strong, diffuse staining with synaptophysin and chromogranin immunohistochemical stains, consistent with neuroendocrine differentiation. No necrosis or mitotic figures are identified. Overall, these findings are diagnostic of a well-differentiated neuroendocrine tumor.  A Ki67 stain shows a proliferation index of ***% (***/500 cells counted), consistent with a WHO grade of ***.

Note: If it is a biopsy, you may opt to report a “provisional” WHO grade (and defer final classification to the anticipated resection specimen).


–   Poorly-differentiated neuroendocrine carcinoma, Large cell type (see comment)

 COMMENT:  Histologic sections of the *** biopsy show infiltration by a proliferation of malignant cells with pleomorphic nuclei and often vesicular chromatin with variably prominent nucleoli. These cells have epithelioid to spindled morphology. There is extensive tumor necrosis and numerous mitotic figures are identified. Immunohistochemical stains demonstrate that the tumor cells stain with synaptophysin, consistent with neuroendocrine differentiation. There is focal staining with chromogranin. The proliferation index by Ki67 is greater than 80%.  Overall, these findings are consistent with the diagnosis of large cell neuroendocrine carcinoma.


  – Poorly-differentiated Neuroendocrine Carcinoma, Small cell type


  – Mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN)


Last updated: August 26, 2019