In the pancreas, poorly differentiated neuroendocrine carcinomas include small cell carcinoma and large cell neuroendocrine carcinoma and are rare; data regarding their pathologic and clinical features are very limited.
One hundred and seven pancreatic resections originally diagnosed as poorly differentiated neuroendocrine carcinomas were reassessed using the classification and grading (mitotic rate/Ki67 index) criteria put forth by the WHO in 2010 for the gastroenteropancreatic system. Immunohistochemical labeling for neuroendocrine and acinar differentiation markers was performed. Sixty-three cases were reclassified, mostly as well differentiated neuroendocrine tumor or acinar cell carcinoma, and eliminated. The clinicopathologic features and survival of the remaining 44 poorly differentiated neuroendocrine carcinomas were further assessed.
The mean patient age was 59 years (range, 21–82) and the male/female ratio was 1.4. Twenty-seven tumors were located in the head of the pancreas, 3 in the body and 11 in the tail. The median tumor size was 4 cm (range, 2–18). Twenty-seven tumors were large cell neuroendocrine carcinomas and 17 were small cell carcinomas (mean mitotic rate, 37/10 HPF and 51/10 HPF; mean Ki67 index, 66% and 75%, respectively). Eight tumors had combined components, mostly adenocarcinomas. In addition, 2 tumors had components of well differentiated neuroendocrine tumor. Eighty-eight percent of the patients had nodal or distant metastatic disease at presentation and an additional 7% developed metastases subsequently. Follow-up information was available for 43 patients; 33 died of disease with a median survival of 11 months (range, 0–104); 8 were alive with disease, with a median follow-up of 19.5 months (range, 0–71). The 2-year and 5-year survival rates were 22.5% and 16.1%, respectively.
Poorly differentiated neuroendocrine carcinoma of the pancreas is a highly aggressive neoplasm, with frequent metastases and poor survival. Most patients die within less than a year. Most (61%) are large cell neuroendocrine carcinomas. Well differentiated neuroendocrine tumor and acinar cell carcinoma are often misdiagnosed as poorly differentiated neuroendocrine carcinoma, emphasizing that diagnostic criteria need to be clearly followed to ensure accurate diagnosis.