Leukemic thyroiditis as the initial relapsing sign in a patient with acute lymphocytic leukemia and blast expression of the neural cell adhesion molecule

We report a patient with a history of T-cell ALL in remission who presented with symptoms and laboratory values consistent with subacute thyroiditis but was found to have leukemic thyroiditis as the first clinical manifestation of leukemic relapse. Bone marrow examination at this time demonstrated recurrent ALL. After successful re-induction with chemotherapy and an allogeneic bone marrow transplant this patient developed an isolated recurrence of her ALL manifested by symptomatic thyromegaly and a new mediastinal mass that was treated with irradiation. Despite no medullary recurrence of ALL, the patient developed pleuritic chest pain and shortness of breath and succumbed to pericardial extramedullary leukemia 9 months later. This to our knowledge is the third reported case of symptomatic ALL involvement of the thyroid gland and the first to be confirmed histologically. Furthermore, this patient had blast expression of the neural cell adhesion molecule (CD56), a cell surface marker that has not been studied in ALL but has previously been identified as a risk factor for extramedullary leukemia (EML) in acute non-lymphocytic leukemia. The authors hypothesize that CD56 expression in this patient might have contributed to her predisposition to EML.