colorectal neuroendocrine carcinoma

PO

Microscopic (histologic) description

 Large cell:

• Organoid arrangement of cells larger than those in small cell carcinoma, with nuclear pleomorphism and hyperchromasia, prominent nucleoli, numerous mitoses and tumor necrosis

 Small cell:

• Resembles pulmonary small cell carcinoma, with sheets and nests of small ovoid cells with minimal cytoplasm, hyperchromatic nuclei with stippled chromatin, nuclear molding with peripheral palisading, brisk mitotic activity, apoptotic cells, necrosis and vascular invasion
• No prominent nucleoli or pleomorphism
• May have Azzopardi effect (encrustation of nuclear material around blood vessels)

Differential diagnosis

 metastatic pulmonary small cell carcinoma:

• No overlying adenoma
• More likely to be TTF1 positive (J Clin Pathol 2010;63:620)

 mixed adenoneuroendocrine carcinoma (MANEC):

• Tumors with neuroendocrine and adenocarcinoma components of at least 30% each (Cancers (Basel) 2012;4:11)

 colorectal adenocarcinoma with scattered neuroendocrine cells:

• Common
• Histology resembles traditional colorectal adenocarcinoma (Arch Pathol Lab Med 1998;122:912)

See also

 colorectal carcinomas
 neuroendocrine carcinomas
 neuroendocrine tumors