Paraspinal extramedullary hematopoiesis in hereditary spherocytosis with a concurrent follicular lymphoma: case report and review of the literature.

We report an unusual case of a 70-year-old male with history of hereditary spherocytosis (HS) and secondary paraspinal extramedullary hematopoiesis with a concurrent follicular lymphoma. The lesion presented as a thoracic paraspinal mass of 9 cm, extending longitudinally between T6 and T9 vertebral bodies. Incisional biopsy revealed that this mass included mature hematopoietic tissue compatible with extramedullary hematopoiesis (EMH). The tissue also presented an extensive and diffuse infiltration by an atypical lymphoid population composed predominantly by small cells. The immunohistochemical study revealed that the atypical lymphoid population had a germinal center phenotype, consistent with the diffuse variant of follicular lymphoma (FL). The simultaneous presence of both EMH and FL in the same lesion made the interpretation and the final diagnosis of this case difficult. The presence of EMH in this clinical context may eclipse the diagnosis of the underlying lymphoproliferative neoplasm. The close association between the tumor cells and extramedullary hematopoietic tissue in the absence of lymphadenopathies or other tissue involvement suggests a relationship of this tumor with the recently described primary FL of the bone marrow.