ABSTRACT Background Accessory spleens result from failure of splenic fusion during development and are occasionally located in the pancreatic tail, radiographically appearing as solid or solid/cystic lesions. Fine needle aspiration ( FNA ) easily identifies accessory spleens in most samples based on architecture and using CD8 to highlight splenic sinusoidal cells. However, in small samples, the architecture is not readily appreciated, and cross‐reactivity with CD8 + T‐cells can create diagnostic challenges. The purpose of the study is to evaluate the utility of steroidogenic factor 1 ( SF1 ) immunohistochemical ( IHC ) staining in identifying accessory spleens. Methods A retrospective search of FNA samples from 2010 to 2023 was performed to collect cases signed out as or consistent with intrapancreatic accessory spleen or splenule. Comparison tissue was collected from the regional lymph nodes. Tissues with no or hypocellular cell blocks were excluded from the study. IHC stains CD8 and SF1 ( EP434 ) Rabbit Monoclonal Primary Antibody were performed on the cell blocks. Results The intrapancreatic accessory spleens (13 cases) were universally positive for both cytoplasmic CD8 and nuclear SF1 in a sinusoidal pattern. The regional lymph nodes (15 cases) showed positivity for CD8 in background lymphocytes (scattered) and were universally negative for SF1. Conclusions While CD8 and SF1 are comparable in their sensitivity, SF1 has benefits in cytologic samples. As a nuclear stain, SF1 is more easily interpreted and better suited for cell transfers. SF1 also eliminates the background CD8 + T cell staining that can be present in lymphoid tissue. Overall, utilization of SF1 can be beneficial in the cytologic workup of an intrapancreatic accessory spleen.
Akinsanya et al. (Mon,) studied this question.