It is an accessory spleen. It is a small mass of tissue that is apart from the spleen that was formed in the development stages or due to trauma. It is better to have it removed as it may cause false medical imaging in the future diagnostics of other problems in the abdominal area.
They are found in about 10%-30% of the population, a nodule of tissue that can be in the body since embryonic growth, and be around 1 cm in diameter. They may result in errors of test reading or bring symptoms after a spleen removal. Otherwise they pose no danger.
An acessory spleen or splenule is a small nodule formed apart from spleen. Splenule is formed of same tissue as of spleen. It forms during the embryonic development. It may be confused for enlarged lymph nodes during diagnosis. Sometimes, after a therapeutic splenectomy, it may show continued symptoms.
If you have your spleen removed due to trauma or enlargement, the splenule can grow in the place of the spleen. The splenule then takes on the spleen's function, so it can be a very, very good thing! A new Spleen!