Marginal zone B-cell lymphoma: lessons from Western and Eastern diagnostic approaches.

Immunoglobulin G4 Thymic Tumor.

Among mediastinal masses, about half are primary tumors in the anterior mediastinum, both benign and malignant. A variety of nonneoplastic lesions (developmental, inflammatory, reactive) can present as a localized mass in this compartment involving the thymus. Ectopic/embryonic remnants also occur in the prevascular compartment of the mediastinum. Rare tumors may develop from each of the multiple tissue types located in this vital area. The purpose of this chapter is to provide a short morphologic/photographic overview of lymphomas and of other rare tumors of mesenchymal type and of germ cell tumors occurring in the thymus or in the anterior mediastinum area. Selected examples of pseudotumors will also be shown. Specific differential diagnostic points are provided, both for “solid” tumors and for hematological malignancies. The main immunohistochemical characteristics of neoplastic/nonneoplastic pathology and updated specific references are discussed.

Lymphomas and Other Rare Tumors of the Thymus

CD30, also known as TNFRSF8 (tumor necrosis factor receptor superfamily member 8), is a protein receptor that is heavily glycosylated inside the Golgi apparatus, as well as a tumor marker that is found on the surface of specific cells in the body, including certain immune cells and cancer ones. This review aims to shed light on the critical importance of CD30, from its emergence in the cell to its position in diagnosing various diseases, including Hodgkin lymphoma, where it is expressed on Hodgkin and Reed–Sternberg cells, as well as embryonal carcinoma, anaplastic large cell lymphoma (ALCL), and cutaneous T-cell lymphoma (CTCL). In addition to its role in positive diagnosis, targeting CD30 has been a promising approach treating CD30-positive lymphomas, and there is ongoing research into the potential use of CD30-targeted therapies for autoimmune disorders. We aim to elaborate on CD30’s roles as a tumor marker, supporting thus the hypothesis that this receptor might be the aim of cytostatic treatment.

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The Polyvalent Role of CD30 for Cancer Diagnosis and Treatment

Thymic hyperplasia with lymphoepithelial sialadenitis-like features is characterized by thymic hyperplasia with lymphocytic infiltrates in the thymic epithelium. The lesion differs from other forms of thymic hyperplasia, including true and follicular thymic hyperplasia, in that it presents at an advanced age and has been reported to be unassociated with autoimmune diseases. We report a case of thymic hyperplasia with lymphoepithelial sialadenitis-like features in a 55-year-old male patient with a history of an immunoglobulin G4 (IgG4)-related disorder. Histologically, the resected mediastinal mass showed features consistent with those of thymic hyperplasia with lymphoepithelial sialadenitis-like features. In addition, the IgG4/IgG ratio was elevated in the polyclonal plasmacytoid infiltration. Thymic hyperplasia with lymphoepithelial sialadenitis-like features has not been reported to be associated with IgG4-related disorders; however, as shown in our report, it is crucial to include it in the differential diagnosis of a mediastinal mass in a patient with IgG4-related disorders.

Thymic Hyperplasia With Lymphoepithelial Sialadenitis-Like Features Arising in a Patient With Immunoglobulin G4-Related Disorders: A Case Report.

IgG4-related disease (IgG4-RD) is a multi-organ immune-mediated chronic fibroinflammatory condition, with unclear certain etiology. It is morphologically characterized by storiform fibrosis, dense IgG4-positive lymphoplasmacytic infiltrate, and obliterative phlebitis. It was recognized as a systemic condition as recently as 2003. IgG4-RD has been described in virtually every organ, forming sclerosing masses, and often mimicking tumors. Clinically, patients present unspecific symptoms and this condition is often recognized incidentally. The epidemiology remains poorly studied, but it has been noted that in the majority of recorded instances, patients are middle-aged men. IgG4-RD could mimic conditions other than tumors, such as infection, inflammation, or other systemic disorders. To ensure accuracy of diagnosis, an exhaustive histopathological analysis is required, together with clinical, radiological, and serological data. Thymic fibrosis in the absence of other primary thymic lesions is a very rare occurrence; in English literature only 1 case has been reported with scattered IgG4 plasma cells infiltrate and focal obliterative phlebitis. We will describe, for the first time, the case of a 49-year-old man displaying an anterior mediastinic, hilar, and intramyocardial mass simulating a sarcoidosis, with a definitive diagnosis of IgG4-related thymic fibrosis extending to the mediastinum and the heart. At the histological examination, we found many features of IgG4-RD in the thymic tissue, such as diffused storiform fibrosis, dense lymphoplasmacytic infiltrate with abundant plasma cells IgG4 positive (ratio IgG/IgG4: 40%), obliterative phlebitis, eosinophilic infiltrate, and Castleman-like lymphoid follicles. We discussed the differential diagnosis and reviewed the literature and the other cases of IgG4-related diseases that had been diagnosed in our department.

Inessa Koptseva de García

Papers

IgG4-related disease in thymus. A very rare case of chronic fibrosis mimicking sarcoidosis.