Background: The histologic diagnosis of pancreatic serous cystadenoma (SCA) is straightforward in most surgically resected specimens. However, in small biopsies, diagnosis could be challenging. Given the increased use of immunohistochemistry, we sought to investigate the expression of neuroendocrine markers in this entity and compare it with pancreatic neuroendocrine tumors (NETs).
Materials and methods: Eighteen NET and 12 SCA cases were collected from our files. The cases were stained with CD56, synaptophysin, and chromogranin A. The percentage of positive cells was recorded. A percentage greater than 10 was considered as the cutoff. Fisher exact test was used for statistical analysis.
Results: For SCA, CD56, synaptophysin, and chromogranin A were expressed in 75%, 92%, and 0% of the cases, respectively, whereas in NET they were expressed in 89%, 100%, and 83%, respectively. Therefore, only chromogranin A could differentiate between these 2 entities based on immunohistochemistry (P=0.003). The entrapped Langerhans islets in the walls of microcysts could be a pitfall.
Conclusions: Our data indicate that a significant proportion of SCA shows positive immunoreaction to CD56 and synaptophysin. Therefore, these markers should be interpreted with caution, particularly in a problematic small biopsy setting.