Accessory spleens are congenital foci of spleen tissue present in body sites outside of the normal spleen. The majority of accessory spleens are found in the splenic hilum and pancreatic tail. They are benign, often incidental findings and share similar histological characteristics to the normal spleen. When an accessory spleen is present in an unusual or rare location, it may be miscategorized, which may lead to unnecessary surgery. Here we report a 55-year-old female with a history of well-differentiated neuroendocrine tumor of the stomach who was found to have a gastric submucosal nodule during a routine upper endoscopy surveillance. Endoscopic ultrasound-guided fine-needle aspiration was performed. It is proven to be an accessory spleen on cytologic examination with immunohistochemical analysis, which showed a sinusoidal pattern of CD8. Retrospectively, we also demonstrated steroidogenic factor 1 (SF-1) expression in sinusoids of gastric accessory spleen for the first time. SF-1 exhibited similar distribution to CD8. It is imperative to provide the correct diagnosis in such cases to avoid unnecessary surgical intervention.
Takeda et al. (Thu,) studied this question.