Diffuse thymic fibrosis: histologic pattern of injury or distinct entity?

Area of Science:

• Pathology
• Immunology
• Thoracic Medicine

Background:

• Primary thymic fibrosis, without other thymic lesions like neoplasms or cysts, is uncommon.
• This condition presents a diagnostic challenge due to its rarity.

Purpose of the Study:

• To describe the clinical and histological features of primary extensive thymic fibrosis.
• To investigate potential associations with IgG4-related sclerosing disease.

Main Methods:

• Retrospective analysis of six cases of primary extensive thymic fibrosis.
• Histopathological examination including assessment of collagen deposition, inflammatory infiltrates, and IgG4-positive plasma cells.
• Review of clinical data, imaging, and intraoperative findings.

Main Results:

• Six cases (3 male, 3 female, mean age 48) of primary extensive thymic fibrosis were identified.
• Lesions were confined to the anterior mediastinum and showed diffuse fibrosis, lymphoplasmacytic infiltrates, and thymic atrophy.
• One case exhibited features overlapping with IgG4-related sclerosing disease, including rare IgG4-positive plasma cells and phlebitis.

Conclusions:

• Primary extensive thymic fibrosis is a distinct entity with potential overlap with IgG4-related sclerosing disease.
• The etiology remains undetermined, but altered immunity or infection may be implicated.
• Further research is needed to elucidate the pathogenesis and clinical significance of this rare condition.