This is a poorly-differentiated neuroendocrine carcinoma of the pancreas (PNEC)
PNECs are rare cancers that occur primarily in the head of the pancreas. Similar to PNETs, most patients with NECs are middle age or older adults, but NECs are slightly more common in men. Pancreatic NECs are malignant tumors and in comparison to WD PNETs have a worse outcome. In contrast to the WD PNETs, NECs are unlikely to be functional. NECs are considered “endocrine in origin” and are positive for at least one of the neuroendocrine tumor markers (staining pattern can be patchy). It is not uncommon for chromogranin stain to be negative in these tumors. Cytomorphologically, PNECs are malignant-appearing and have a high rate of cellular turnover with brisk apoptosis, numerous mitoses and a variable degree of necrosis. In contrast to WD PNETs, PNECs are less likely to be associated with the hereditary syndromes stated in the discussion following case 1 but more likely to harbor aberrancy of P53 and Rb or Bcl-2 expression. PNECs are thought to arise in association with or from squamous cell carcinomas or adenocarcinomas. Histologic variants of NECs include large cell and small cell (although both rare, in the pancreas, the large cell is more common than the small cell variant):
- Large cell variant has large nuclei with prominent nucleoli or vesicular chromatin and abundant cytoplasm. Tumors can have organoid or diffuse growth patterns or contain palisading and pseudo-papillary configurations in various proportions.
- Small cell variant has small to medium sized cells with increased nuclear to cytoplasmic ratio and irregular nuclei with immature or finely speckled chromatin and hyperchromatic indistinct nucleoli. There is nuclear molding or smudging. Tumors may grow in sheets, ribbons or clusters.
For PNECs, biochemical abnormalities are rare, and therefore labs and 68Ga-dotatate scans are typically not indicated. However, brain MRI and PET/CT are indicated, similar to the evaluation of small cell carcinoma of other sites including lung.
Is the same staging criteria used for PNECs and WD PNETs? No. Pancreas Exocrine staging protocol should be utilized for PNEC but Pancreas Endocrine staging protocol should be utilized for WD PNETs.
Patient 2 completed 6 cycles of cisplatin and etoposide following his Whipple. Fifteen months later, surveillance imaging revealed asymptomatic liver metastases. Image-guided biopsy proved recurrent poorly-differentiated neuroendocrine carcinoma in the posterior segment of the right hepatic lobe (max dimensions of 4.0 and 2.8 cm).