"Hamartoma" of the spleen (splenoma) in children

Hamartomas of the spleen or splenomas, are uncommon benign tumorous growths in this organ which have not been well characterized in children. We report four patients, 4 to 11 years old, who had splenomegaly and splenic "hamartomas" associated with different hematologic conditions (refractory microcytic anemia, sickle cell anemia, hereditary spherocytosis, and dyserythropoietic hemolytic anemia). All patients had total splenectomy as a primary therapeutic approach or to lessen their transfusion requirements. In only one patient was a focal splenic mass identified preoperatively with contrasted computed tomography (CT) scans and magnetic resonance imaging (MRI). None of the patients showed a mass by ultrasonography. Gross examination showed enlarged spleens (315-724 g) which on cut surface revealed a single nodule in one and multiple bulging nodules in three specimens. The nodules varied from 1.3 to 7 cm and were indistinct from the surrounding nonlymphoid splenic (i.e., red pulp) parenchyma. Histology of the nodules showed red splenic pulp with variable histiocytic proliferation, focal extramedullary hematopoiesis, lympho-plasmacytosis, fibrosis, and siderotic-calcific deposits. Intranodular small T- and B-cell lymphoid aggregates but no organized secondary follicles or periarteriolar sheaths were seen. Proliferation antigen Ki-67 (Mib-1) immunostains showed a low (< 5%) proliferation index in the nodules and surrounding tissue. Reticulin stains did not show a capsule or border between the normal spleen and the nodules. The critical histologic differential diagnosis for these lesions is with benign vascular tumors. These can be identified by their more disorderly pattern, by immunohistochemistry and by their higher proliferation index. It is our contention that these splenic nodules are not true hamartomas, as they seem to result from remote ischemic or infectious/inflammatory insults, leading to the fibro-inflammatory reaction and deposition of calcium and hemosiderin that is better designated with the descriptive term of splenoma. Review of the literature and our own experience indicates that most children with splenic hamartomas or splenomas as we prefer to call them, have an underlying hematologic disorder likely made worse by a state of hypersplenism that explains the consistent improvement in the blood values after splenectomy.