Introduction: Hamartoma of the spleen is a rare, sometimes asymptomatic similar to hemangioma benign tumor of the spleen, which, owing to the new diagnostic imaging methods, is discovered with increasing frequency. It appears as solitary or multiple tumorous lesions.
Case outline: We present a 48-year-old woman in whom, during the investigation for Helicobacter pylori gastric infection and rectal bleeding, with ultrasonography, a mass 6.5x6.5 cm in diameter was discovered by chance within the spleen. Splenectomy was performed due to suspected lymphoma of the spleen. On histology, tumor showed to be of mixed cellular structure, with areas without white pulp, at places with marked dilatation of sinusoids and capillaries to the formation of "blood lakes" between which broad hypercellular Billroth's zones were present. Extramedullary hematopoiesis was found focally. The cells that covered vascular spaces were CD34+ and CD31+ and CD8- and CD21-.
Conclusion: Hamartoma has to be taken into consideration always when well circumscribed hypervascular tumor within the spleen is found, particularly in children. Although the diagnosis of hamartoma may be suspected preoperatively, the exact diagnosis is established based on histological and immunohystochemistry examinations. Treatment is most often splenectomy and rarely a partial splenectomy is possible, which is recommended particularly in children.