title: Tumor-like massive thymic hyperplasia in childhood: a possible defect of T-cell maturation, histological and cytoenzymatic studies of three cases.
abstract: Contrary to the transitory, enlarged thymic shadow commonly observed in babies, tumor-like Massive Thymic Hyperplasia (MTH) is seldom encountered in infancy and even more rarely in children over 4 years. We present three cases of MTH affecting 10, 5 and 11 years old girls in whom the tremendous enlargement of the thymus (3 to 4 times the normal) led to consideration of a diagnosis of a genuine tumoral process and to either biopsy or surgical removal of the thymic mass. Optical histological examination showed a perfectly normal thymic tissue and indicated that MTH was linked with a simple and homogeneous hyperplasia of the lymphoid cells. Using the dot-like acid alpha-naphtyl acetate esterase (ANAE) as a marker of mature T cells, quantitative and comparative cytoenzymatic studies revealed a definite reduction of ANAE +, mature T cells in the cortical and medullary areas in MTH (p less than or equal to 0.001). These findings suggest that MTH represents an intrathymic accumulation of immature T cells, a condition which may express a failure of cell differentiation perhaps connected with some thymic hormonal insufficiency.
mesh_terms: D002454:Cell Differentiation; D002648:Child; D002675:Child, Preschool; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D009283:Naphthol AS D Esterase / Q000378:metabolism; D013601:T-Lymphocytes / Q000201:enzymology / Q000473:pathology*; D013952:Thymus Hyperplasia / Q000201:enzymology / Q000473:pathology*
chemical_list: D009283:Naphthol AS D Esterase