Table 3.

Required and recommended reporting elements for biopsies and resections of gastroenteropancreatic neuroendocrine epithelial neoplasms

	Associated Required or Recommended Immunohistochemistry
Required Data Element:
Diagnosis: well-differentiated neuroendocrine tumor or poorly differentiated neuroendocrine carcinoma	● Synaptophysin and chromogranin A to establish neuroendocrine nature (required) ● Broad-spectrum keratin to confirm epithelial nature (highly recommended in primary and regional disease and required in distant metastasis) ● p53 and Rb are recommended in the distinction of well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma
Ki-67 proliferation index (proliferation index >20% is implied for poorly differentiated neuroendocrine carcinoma and performance is not mandatory)	● Ki-67 on at least 1 block of tumor (required) ● Ki-67 on at least1 block of primary tumor and matched metastasis (recommended)
Mitotic count per 10 HPF (in biopsies with <50 HPF to assess it is reasonable to express the total number of mitotic figures in the total number of microscopic fields; for poorly differentiated neuroendocrine carcinoma a mitotic count >20 per 10 HPF is implied and performance is not mandatory)
Grade: G1, G2, or G3 (G3 is implied for poorly differentiated neuroendocrine carcinoma and need not be explicitly stated)
Data elements in College of American Pathologists Cancer Protocol: for resection specimens
Recommend Data Element:
Comment on site of origin (for metastasis of occult origin)	● Panel in a well-differentiated neuroendocrine tumor may include some combination of CDX2 for midgut origin; polyclonal PAX8 and/or PR (or islet 1 and PAX6) for pancreatic origin; TTF-1 (or OTP) for bronchopulmonary origin; and SATB2 for rectal origin ● Panel in a poorly differentiated neuroendocrine carcinoma to include TTF-1 for visceral origin and CK20 for cutaneous origin; neurofilament and strong SATB2 expression also support a cutaneous origin