There is a 2cm well-defined spherical structure with homogeneous enhancement and mild FDG avidity (SUV_max 1.3) located in the peritoneum of the upper anterior abdomen.

Differential diagnoses included peritoneal metastastic nodule or nodal metastasis. 

Splenunculi, or accessory spleens are common, occurring in up to 20% of the population. They may occur as single or multiple, and may occur congenitally or as a result of splenectomy or trauma. They may be overlooked during splenectomy, which is of particular clinical significance when the splenectomy was performed for a haematological disorder. In this case, the splenunculus may have occurred post splenectomy, or may have been congenital and overlooked during splenectomy.

Splenunculi are histologically and functionally identical to the spleen. They occur in the gastrosplenic ligament, around the tail of pancreas, and in the omenta and mesenteries. Splenic FDG uptake is usually mild and diffuse, equal to or less than that of liver, and splenunculi are known to follow this same pattern of uptake. Thus they are an important cause of false positive diagnosis in the assessment for malignancy, as occurred in this case. Awareness of splenunculi as a cause for focal FDG avidity is important to avoid unnecessary invasive procedures such as biopsy or surgery.