Long Survival and Prolonged Remission after Surgery and Chemotherapy in a Metastatic Mismatch Repair Deficient Pancreatic Neuroendocrine Carcinoma with MLH1/PMS2 Immunodeficiency and Minimal Microsatellite Shift

We describe a 62-year-old patient who underwent pancreaticoduodenectomy for a NEC located in the pancreatic head, with peripancreatic lymph node metastases. Tumor necrosis was prominent and the Ki67 proliferative index was 60%. One year after the diagnosis, the patient experienced recurrence with a left supraclavicular lymph node metastasis, which was surgically removed, followed by standard cisplatin-etoposide chemotherapy. Neoplastic cells showed combined loss of expression of MLH1 and PMS2 in both primary tumor and lymph node metastasis. Microsatellite instability (MSI) test using a mononucleotide repeats pentaplex PCR (BAT-25, BAT-26, NR-21, NR-22, and NR-24) revealed minimal mononucleotide shifts showing deletion of less than 3  bp at NR-21, BAT-26, NR-24, and NR-22 loci. MLH1 methylation analysis revealed absence of the gene promoter methylation.BRAF andKRAS mutations were not detected. In gut, NECs ’ mismatch repair deficiency phenotype has been reported in about 10% of cases, and it represents an independent factor of more favorable outcome. Likewise, our patient is currently alive with a follow-up of more than 12 years after pancreaticoduodenectomy, by itself an unexpected finding for suc h an aggressive neoplasm.
Source: Endocrine Pathology - Category: Pathology Source Type: research