Massive Thymic Hyperplasia Mimicking Lymphoma: A Case Report and Review of Literature

Abstract

Purpose: A case of massive thymic hyperplasia presenting as a large anterior mediastinal mass is
reported. Patient: A 4-year-old Thai boy presented with an acute febrile illness and respiratory
symptoms and later transferred to our institute when an anterior mediastinal mass with right upper
lung infiltration was detected in chest roentgenogram. Results: A computed tomography scan of
the chest revealed a large homogenous anterior mediastinal mass. All laboratory studies for the
patient including routine hematology, chemistry studies as well as biological tumor marker studies
such as alpha- fetoprotein, beta- human chorionic gonadotropin and lactic dehydrogenase were
within normal limits. A bone marrow aspiration showed no evidence of malignancy. The diagnosis
was made by an open incision biopsy, which showed normal thymic tissue. The patient was
discharged without any medication and asked to follow-up three weeks later. On his return, his
thymic image showed a spontaneous resolution in size. Conclusions: Massive thymic hyperplasia
is a rare cause of mediastinal mass during the first two decades of life, however, should be consid-
ered in the differential diagnosis especially if there is no evidence of mass compression or any
positivity of tumor markers.