thymic hyperplasia

thymic hyperplasia

A generic term for an increase in size and weight of the thymus, which may be true hyperplasia (e.g., rebound hyperplasia post-chemotherapy) or “pseudohyperplasia”, in which the normal architectural is maintained with a marked increase in germinal centres, often associated with autoimmune disease (in particular myasthenia gravis).
References in periodicals archive ?
Histologically, thymic hyperplasia can be divided into two distinct types: true hyperplasia and lymphoid (follicular) hyperplasia.
The chemical shift ratio (CSR) may be used to compare relative changes in the signal intensity of thymic tissue, relative to the paraspinal muscles, in opposed-phase and in-phase images: This method is useful in differentiating thymic hyperplasia from a neoplasm when encountering a mass in the anterior mediastinum.
It has been suggested that certain fat-suppression MRI techniques, namely chemical shift imaging, are useful in differentiating thymic hyperplasia from other solid thymic lesions.
Since thymic hyperplasia contains fat, the CSR is higher.
For example, thymic extension into the superior mediastinum in patients with thymic hyperplasia and neurofibromas can both show FDG-avidity on the PET scan (Figure 18).
Thymic hyperplasia is not an ordinary manifestation of Graves disease (GD).
Thymic hyperplasia related to GD was suggested, and follow up was recommended.
The etiologic role of GD in thymic hyperplasia is not clear.
The differential diagnosis includes thymoma, massive thymic hyperplasia, teratoma, thyroid goiter, and lymphoma.
The normalization of lymphocytosis that occurs with resection of both massive thymic hyperplasia and thymolipoma lends some credibility to this theory.
Ectopic thymic tissue, like its normal counterpart, may also undergo transformation to thymic hyperplasia or even thymic neoplasms.
True thymic hyperplasia is diagnosed when there is >50% increase in thymic volume over baseline, usually within a year of the stress period, with preserved microscopic features.