Thymic Extranodal Marginal Zone Lymphoma of Mucosa-associated Lymphoid Tissue with 8q24 Abnormality

From the archives of MD Anderson Cancer Center Castleman disease involving the thymus gland: Case report and literature review

Castleman disease is a nodal based disease and very rarely involves the thymus gland. We report a 52-year-old man who was found incidentally to have a single thymic mass by computerized tomography scan. Thymectomy was performed, and the gross specimen showed a well-circumscribed, multi-loculated cystic mass. Histologic examination showed thymus involved by Castleman disease, hyaline-vascular variant. The lesion was characterized by lymphoid follicles with wide mantle zones, variably lymphocyte-depleted germinal centers with sclerotic radial blood vessels, and prominent interfollicular/stromal changes including numerous endothelial venules with sclerotic walls and hyaline sclerosis, scattered and frequent dysplastic follicular dendritic cells and foci of dystrophic calcification. Immunohistochemical analysis showed that the follicle mantle zones were composed of numerous B-cells positive for CD20, PAX5, and IgD. Antibodies specific for CD21 and CD23 highlighted prominent follicular dendritic cell networks within follicles. There was no evidence of human herpes virus 8. We searched the literature and could identify only 10 additional cases of thymic CD. Previously reported cases included 8 unicentric and 2 multicentric, classified pathologically as plasma cell variant (n = 4), hyaline vascular variant (n = 3), and mixed (n = 3). Thymectomy, as was done in the currently reported case, most often leads to the diagnosis of Castleman disease and was a mainstay of treatment in other reported cases.

Mucosa-associated lymphoid tissue lymphoma in thymus: a SEER analysis

OBJECTIVES

The present study explores an extremely rare disease, thymic mucosa-associated lymphoid tissue (MALT) lymphoma, for its characteristics and prognostic factors by analyzing the Surveillance, Epidemiology, and End Results (SEER) database.

METHODS

From 2000 to 2018, cases with a diagnosed thymic MALT lymphoma were extracted. Clinical characteristics, treatments, and survival patterns of these cases were analyzed.

RESULTS

Thymic MALT lymphoma (n = 26) accounted for 0.09% of all MALT lymphomas. With a sex ratio of 0.53 (male/female), 68% white population was affected. Most cases were diagnosed with Ann Arbor stage I (50%), yet advanced-stage did not show worse prognosis (p = 0.236). Different treatment protocols did not influence the overall prognosis (p > 0.99). The 5- and 10- year overall survival rates were 83.1% and 78.2%, respectively. Older than 70 years may be an independent risk factor for overall survival (HR = 7.166 [95% CI 1.173-43.756], p = 0.033).

CONCLUSION

Thymic MALT lymphoma is a highly rare disease with a favorable prognosis. Ann Arbor staging might not be appropriate to classify severity of this disease or its treatment. Older people may have worse survival. A standardized treatment mode needs to be established, and surgery could remain as the mainstay.

Cutaneous mucosa-associated lymphoid tissue lymphoma complicating Sjögren's syndrome: A case report and review of literature

BACKGROUND

The association of Sjögren's syndrome (SS) and lymphoma is similar. Mucosa-associated lymphoid tissue (MALT) or extranodal marginal zone B-cell lymphoma was the most common lymphomatous histology in SS patients. MALT in SS patients is frequently located in the parotid gland, while MALT lymphoma of the skin with SS is an exceedingly rare entity that needs to be recognized.

CASE SUMMARY

A 60-year-old woman presented with a 3-year history of progressive dry mouth associated with a 1-year history of enlarging cutaneous nodules. Physical examination revealed two hard subcutaneous nodules on her right lower leg. The results of Schirmer’s test were positive, despite the absence of dry eyes. Labial salivary gland biopsy revealed lymphocytic infiltration and chronic inflammation with a focus score of 2. The patient was diagnosed with SS. She underwent resection of one cutaneous nodule, and histopathological analysis identified the nodule as MALT lymphoma. Her dry mouth symptoms improved, and the nodules decreased after 6 mo of treatment with hydroxychloroquine sulfate and chemotherapy (thalidomide, cyclophosphamide, and dexamethasone).

CONCLUSION

Lymphoma is a severe complication of SS, shown by the reported unique case of cutaneous MALT lymphoma with SS.

Characterization of molecular genetics and clinicopathology in thymic MALT lymphoma

Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) lymphoma is a type of low-grade malignant B-cell lymphoma. The aim of this study was to investigate the clinicopathological characteristics of thymic MALT lymphoma. We analyzed the clinical, morphological, immunophenotypical, cytogenetic, and molecular characteristics of 11 cases of thymic MALT lymphoma. The relevant literature was also reviewed. The median age of the 11 patients was 50 (range: 33-60). There was a female predominance with a female-to-male ratio of 10:1. Three patients presented with Sjögren syndrome, autoimmune thrombocytopenia purpura, and type B1 thymoma, respectively. Microscopically, thymic MALT lymphoma was characterized by epithelium-lined cysts that were surrounded by small lymphocytes, centrocyte-like cells, and monocytoid B-cells. Plasmacytic differentiation was observed in two cases. The tumor cells expressed CD20, CD79α, and BCL2. Clonal immunoglobulin genes were detected in all 8 examined cases. Fluorescence in situ hybridization (FISH) for 18q21 was performed in 7 cases, and no translocations involving 18q21 were found. Targeted gene sequencing was performed in five cases with available DNA samples, and TNFAIP3, CARD11, IGLL5, and CCND3 mutations were identified. Thymic MALT lymphoma is a rare type of B cell malignancy with a female predominance and excellent clinical outcomes. Molecular aberrations involving the NF-κB pathway are frequent in thymic MALT lymphoma, suggesting that dysregulation of the NF-κB pathway is an important mechanism underlying the pathogenesis of thymic MALT lymphoma.

Mediastinal Lymphoproliferative Disorders

Lymphoproliferative disorders comprise 50% to 60% of all mediastinal malignancies in both children and adults. Primary mediastinal involvement is rare (∼5%), whereas secondary mediastinal involvement by systemic disease is more common (10% to 25%). Primary mediastinal disease is defined as involvement by a lymphoproliferative disorder of mediastinal lymph nodes, the thymus, and/or extranodal mediastinal organs without evidence of systemic disease at presentation. In this review, the clinical, radiologic, histopathologic, immunohistochemical, and genetic features of some of the most characteristic mediastinal lymphoproliferative disorders are presented. The entities discussed here include: classic Hodgkin lymphoma with emphasis on nodular sclerosis and mixed cellularity types, and non-Hodgkin lymphomas, including primary mediastinal (thymic) large B-cell lymphoma, mediastinal gray zone lymphoma, mediastinal diffuse large B-cell lymphoma, thymic marginal zone lymphoma, mediastinal plasmacytoma, T-lymphoblastic lymphoma, and anaplastic large cell lymphoma. Although not a malignant process, hyaline vascular Castleman disease is also discussed here as this disorder commonly involves the mediastinum. Despite multiple advances in hematopathology in recent decades, the day-to-day diagnosis of these lesions still requires a morphologic approach and a proper selection of immunohistochemical markers. For this reason, it is crucial for general pathologists to be familiar with these entities and their particular clinicoradiologic presentation.

Primary Mediastinal Nodal and Extranodal Non-Hodgkin Lymphomas: Current Concepts, Historical Evolution, and Useful Diagnostic Approach: Part 2

Primary mediastinal non-Hodgkin lymphomas (PM-NHLs) represent ∼5% of all non-Hodgkin lymphomas (NHLs) and comprise lymphomas of B-cell and T-cell origin. PM-NHLs are defined as involvement of mediastinal lymph nodes, thymus, and/or mediastinal organs (heart, lung, pleura, pericardium) by NHL without evidence of systemic disease at presentation. The clinical scenario is variable and depends on the lymphoma subtype. The radiologic presentation is also variable ranging from a mediastinal mass with or without superior vena cava syndrome, a pleural or a cardiac mass associated with effusion, or as an effusion only. The diagnosis of PM-NHLs can only be established by microscopic evaluation, and therefore, general pathologists should be aware of these tumors and familiar with their diagnostic approach. The most common anterior mediastinal NHLs (90% to 95%) are primary mediastinal (PM) large B-cell lymphoma and T-lymphoblastic lymphoma. Thymic marginal zone lymphoma and mediastinal gray zone lymphoma are very rare. The remainder PM-NHLs involving middle or posterior mediastinum include diffuse large B-cell lymphoma (DLBCL) and rare cases of T-cell lymphoma, including anaplastic large cell lymphoma and breast implant-associated anaplastic large cell lymphoma extending to the anterior mediastinum. Primary pleural and cardiac NHLs are mostly DLBCLs. Other rare subtypes of PM-NHLs include DLBCL associated with chronic inflammation/pyothorax-associated lymphoma, fibrin-associated DLBCL (both Epstein-Barr virus positive), and pleural and/or pericardial primary effusion lymphoma (human herpesvirus-8 positive/Epstein-Barr virus positive). We review the historical aspects, epidemiology, clinicoradiologic features, histopathology, immunohistochemistry, differential diagnosis, and relevant cytogenetic and molecular features of the remaining mediastinal B-cell lymphomas, including primary thymic marginal zone lymphoma of the mucosa-associated lymphoid tissue type, other PM small B-cell lymphomas, PM plasmacytoma, and the most relevant PM T-cell lymphomas.