“After traumatic splenic injury or splenectomy, small isolated spleens may develop. These implants are not limited to the left upper quadrant, and splenosis in other locations can mimic other pathologic entities. This pictorial essay presents the range of appearances of intraabdominal and pelvic splenosis.”
CT of splenosis: patterns and pitfalls.
Lake ST, Johnson PT, Kawamoto S, Hruban RH, Fishman EK.
AJR 2012 Dec;199(6)W686-93

Accessory Spleens Enhance like Normal Splenic Tissue on both arterial and venous phase images

“CT can be used to differentiate between IPAS and PanNET with good specificity and sensitivity. The IPAS mirrors the spleen’s enhancement and is usually located along the dorsal surface of the pancreas.”
Intrapancreatic Accessory Spleen: Possibilities of Computed Tomography in Differentiation From Nonfunctioning Pancreatic Neuroendocrine Tumor 
Coquia SF, Kawamoto S, Hruban RH, Fishman EK
J Comput Assist Tomogr. 2014 Nov-Dec;38(6):874-8

“Although not statistically significant, several other findings are also helpful to differentiate IPAS and neuroendocrine tumors. All IPASs in this study were located at the tip or within 3 cm of the tip of the tail of the pancreas. Therefore, if an enhancing mass is seen more than several centimeters from the tip of the tail of the pancreas, it is less likely to represent IPAS and more likely a neuroendocrine tumor.”
Intrapancreatic Accessory Spleen: Possibilities of Computed Tomography in Differentiation From Nonfunctioning Pancreatic Neuroendocrine Tumor 
Coquia SF,Kawamoto S, Hruban RH, Fishman EK
J Comput Assist Tomogr. 2014 Nov-Dec;38(6):874-8

“In cases where the reader finds the lesion as indeterminate, although most were ultimately PanNETs in our study, given the associated decline in overall reader specificity seen in our study, the CT reader should recommend confirmatory testing such as 99mTc-labeled heat-damaged red blood cell scintigraphy or MRI rather than an observation with fine needle aspiration as needed for confirmation.”
Intrapancreatic Accessory Spleen: Possibilities of Computed Tomography in Differentiation From Nonfunctioning Pancreatic Neuroendocrine Tumor
Coquia SF,Kawamoto S, Hruban RH, Fishman EK
J Comput Assist Tomogr. 2014 Nov-Dec;38(6):874-8

“Ten patients of 303 patients who underwent a distal pancreatectomy were identified with a final pathology of IPAS. The average age was 54 y, 80% were white, and 60% were male. Lesions ranged in size from 7 mm to 5.1 cm in largest diameter (mean 2.2 cm). Lesions were described as round, well-marginated, and enhancing masses within the pancreatic tail. Preoperative workup was variable in terms of imaging and laboratory testing. Diagnostic workups were examined and combined with multidisciplinary input to create a diagnostic algorithm.”
Pancreatic Incidentalomas: A Management Algorithm for Identifying Ectopic Spleens 
Baugh KA et al.
J Surg Res. 2019 Apr;236:144-152