Diffuse Thymic Fibrosis Histologic Pattern of Injury or Distinct Entity?

Department of Pulmonary and Mediastinal Pathology, Armed Forces Institute of Pathology, Washington, DC 20306, USA.
The American journal of surgical pathology (Impact Factor: 5.15). 02/2010; 34(2):211-5. DOI: 10.1097/PAS.0b013e3181c91301
Source: PubMed


Thymic fibrosis in the absence of another primary thymic lesion, such as a neoplasm or cyst, is unusual. We identified 6 cases of primary extensive thymic fibrosis that developed in 3 men and 3 women, aged 28 to 60 years, mean 48 years. Patients had limited or no symptoms. Two patients had dyspnea and 1 had cough and hemoptysis. One female patient had myasthenia gravis. The lesions measured 3.5 to 17 cm in greatest dimension, mean 8 cm, and were confined to the anterior mediastinum as determined by imaging, intraoperative notes, and/or gross examination. All cases showed diffuse fibrosis with variable collagen deposition, lymphoplasmacytic infiltrates, and involution/atrophy of thymus. One case had rare IgG4-positive plasma cells and focal obliterative phlebitis. The histology showed overlap with that of IgG4-related sclerosing disease, which to our knowledge has not been documented earlier in this location. Although the etiology of the lesions is undetermined, altered immunity and/or infection may play a role.

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    ABSTRACT: The paper describes a case of generalized lymphadenopathy clinically recognized as malignant lymphoma in a 59-year-old woman. Her death occurred from bilateral pneumonia. Autopsy also showed a tumor-like mass in the thymus. On histological examination, the lymph nodes, thymus, and spleen exhibited an intensive polyclonal IgG4+ plasma cell infiltration. Lymphoid plasma cell infiltration with increased count of IgG+ plasma cells, progressive sclerosis, and phlebitis obliterans were found in the pancreas and peripancreatic adipose tissue, liver, kidney, epicardium, thyroid, pituitary, skin, and other organs. The case was regarded as IgG4-related sclerosing disease manifesting itself as lymphadenopathy and thymus enlargement.
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