Background. Microsatellite instability (MSI) has emerged as a predictive biomarker for immune checkpoint inhibitor therapy. Cancer heterogeneity represents a potential obstacle for the analysis of predicitive biomarkers. MSI has been reported in pancreatic cancer, but data on the possible extent of intratumoral heterogeneity are lacking. Methods. To study MSI heterogeneity in pancreatic cancer, a tissue microarray (TMA) comprising 597 tumors was screened by immunohistochemistry with antibodies for the mismatch repair (MMR) proteins MLH1, PMS2, MSH2, and MSH6.

No abstract

Mucin 5AC (MUC5AC) is a secreted gel-forming mucin expressed by several epithelia. In the colon, MUC5AC is expressed in scattered normal epithelial cells but can be abundant in colorectal cancers. To clarify the relationship of MUC5AC expression with parameters of tumor aggressiveness and mismatch repair deficiency (dMMR) in colorectal cancer, a tissue microarray containing 1812 colorectal cancers was analyzed by immunohistochemistry. MUC5AC expression was found in 261 (15.7%) of 1,667 analyzable colorectal cancers. MUC5AC expression strongly depended on the tumor location and gradually decreased from proximal (27.4% of cecum cancers) to distal (10.6% of rectal cancers; p < 0.0001). MUC5AC expression was also strongly linked to dMMR. dMMR was found in 21.3% of 169 cancers with MUC5AC positivity but in only 4.6% of 1051 cancers without detectable MUC5AC expression (p < 0.0001). A multivariate analysis showed that dMMR status and tumor localization predicted MUC5AC expression independently (p < 0.0001 each). MUC5AC expression was unrelated to pT and pN status. This also applied to the subgroups of 1136 proficient MMR (pMMR) and of 84 dMMR cancers. The results of our study show a strong association of MUC5AC expression with proximal and dMMR colorectal cancers. However, MUC5AC expression is unrelated to colon cancer aggressiveness.

Objectives Information of the clinicopathological characteristics and outcome data of patients with adenosquamous carcinoma of the pancreas (ASCAP) remains limited. This study's aim is to describe the clinical, pathological, and molecular characteristics of 25 resected ASCAPs. Methods Of all 25 cases, patient characteristics, follow-up data, and pathological/immunohistological features were reviewed and analyzed. Results In this 3-institutional retrospective analysis of 562 pancreatic cancer patients, we identified 25 cases with histologically confirmed ASCAP (4.4%). Follow-up was available in 21 ASCAP and 50 pancreatic ductal adenocarcinoma control patients with a median overall survival of 8.2 and 21 months, respectively. Age, tumor size, localization in the tail, lymph node status, and resection margin seem to be the most significant factors of survival in our ASCAP cohort. In contrast to pancreatic ductal adenocarcinoma, positive expression of p63, keratins K5/14, and the epidermal growth factor receptor are a robust marker profile of these tumors. Conclusions Adenosquamous carcinoma of the pancreas comprises a group of neoplasms in which stage and adverse morphological features contribute to its bad prognosis. Further work must be pursued to improve detection and treatment options to reduce mortality. Specifically, differences in biology might become a target for the development of possible therapies.

Background DOG1 (ANO1; TMEM16A) is a voltage-gated calcium-activated chloride and bicarbonate channel. DOG1 is physiologically expressed in Cajal cells, where it plays an important role in regulating intestinal motility and its expression is a diagnostic hallmark of gastrointestinal stromal tumors (GIST). Data on a possible role of DOG1 in pancreatic cancer are rare and controversial. The aim of our study was to clarify the prevalence of DOG1 expression in pancreatic cancer and to study its association with parameters of cancer aggressiveness. Methods DOG1 expression was analyzed by immunohistochemistry in 599 pancreatic cancers in a tissue microarray format and in 12 cases of pancreatitis on large tissue sections. Results DOG1 expression was always absent in normal pancreas but a focal weak expression was seen in four of 12 cases of pancreatitis. DOG1 expression was, however, common in pancreatic cancer. Membranous and cytoplasmic DOG1 expression in tumor cells was highest in pancreatic ductal adenocarcinomas (61% of 444 interpretable cases), followed by cancers of the ampulla Vateri (43% of 51 interpretable cases), and absent in 6 acinus cell carcinomas. DOG1 expression in tumor associated stroma cells was seen in 76 of 444 (17%) pancreatic ductal adenocarcinomas and in seven of 51 (14%) cancers of the ampulla Vateri. Both tumoral and stromal DOG1 expression were unrelated to tumor stage, grade, lymph node and distant metastasis, mismatch repair protein deficiency and the density of CD8 positive cytotoxic T-lymphocytes in the subgroups of ductal adenocarcinomas and cancers of ampulla Vateri. Overall, the results of our study indicate that DOG1 may represent a potential biomarker for pancreatic cancer diagnosis and a putative therapeutic target in pancreatic cancer. However, DOG1 expression is unrelated to pancreatic cancer aggressiveness.