Low-grade B cell lymphoma of mucosa-associated lymphoid tissue in the thymus of a patient with rheumatoid arthritis

The Multifaceted Roles of B Cells in the Thymus: From Immune Tolerance to Autoimmunity

The thymus is home to a significant number of resident B cells which possess several unique characteristics regarding their origin, phenotype and function. Evidence shows that they originate both from precursors that mature intrathymically and as the entry of recirculating mature B cells. Under steady-state conditions they exhibit hallmark signatures of activated B cells, undergo immunoglobulin class-switch, and express the Aire transcription factor. These features are imprinted within the thymus and enable B cells to act as specialized antigen-presenting cells in the thymic medulla that contribute negative selection of self-reactive T cells. Though, most studies have focused on B cells located in the medulla, a second contingent of B cells is also present in non-epithelial perivascular spaces of the thymus. This latter group of B cells, which includes memory B cells and plasma cells, is not readily detected in the thymus of infants or young mice but gradually accumulates during normal aging. Remarkably, in many autoimmune diseases the thymus suffers severe structural atrophy and infiltration of B cells in the perivascular spaces, which organize into follicles similar to those typically found in secondary lymphoid organs. This review provides an overview of the pathways involved in thymic B cell origin and presents an integrated view of both thymic medullary and perivascular B cells and their respective physiological and pathological roles in central tolerance and autoimmune diseases.

MALT Lymphoma of the Urinary Bladder Shows a Dramatic Female Predominance, Uneven Geographic Distribution, and Possible Infectious Etiology

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) of the urinary bladder is an extremely rare entity accounting for 0.2% of all malignant urinary bladder neoplasms, and the diagnosis could be challenging. We present here a patient with urinary bladder MALT lymphoma and review of all published case reports in the literature. We summarized the reported immunophenotype of the neoplasm, ancillary studies, therapy, and follow-up for all 59 patients in the table. The median patients’ age was 57 years-old (range, 17 to 88), with female predominance in 50 of 59 patients representing a 1:5.6 ratio. Geographical distribution of the reported patients was as follows: 22 from Asia, of which more than a half (16) originated from Japan; 28 from Europe, of which 19 reported from the United Kingdom, and 3 patients were reported from the United States (including our patient). Twenty-three (77%) of 30 patients, for whom their clinical presentation was recorded, had symptoms of cystitis; Escherichia coli was the most common pathogen. We concluded that a prominent female predominance, uneven geographic distribution of urinary bladder MALT lymphoma, and a success of antibacterial therapy in selected cases suggest the link between urinary tract infection and urinary bladder MALT lymphoma.

Four cases of invasive anterior mediastinal tumors definitively diagnosed by the chamberlain procedure

Percutaneous needle biopsy, commonly used for a definitive diagnosis of anterior mediastinal tumors, is sometimes inconclusive because of the small size of the biopsy specimens and the histologic heterogeneity of the tumors. We herein report 4 cases of invasive anterior mediastinal tumors, in which the definitive diagnosis was made using the Chamberlain procedure. [Case 1] A 33-year-old man was found to have an anterior mediastinal tumor on chest X-ray and computed tomography (CT). The tumor was histologically diagnosed as thymic carcinoma (squamous cell carcinoma) using the Chamberlain procedure. After 3 courses of preoperative chemotherapy, the patient underwent surgery and postoperative radiotherapy. He remains well, 35 months after the biopsy. [Case 2] A 17-year-old boy was found to have a tumor in the anterior mediastinum on chest CT. His serum alpha-fetoprotein level was elevated to 2,461 ng/mL. Histological diagnosis of yolk sac tumor was confirmed using the Chamberlain procedure. He was treated with one course of chemotherapy, followed by surgery; he remains well 57 months after the biopsy. [Case 3] A 72-year-old man was found, on chest X-ray and CT, to have a left upper anterior mediastinal tumor with invasion of the subclavian vessels. The tumor was confirmed histologically as thymic (sarcomatoid) carcinoma using the Chamberlain procedure. Despite 2 courses of chemotherapy, the tumor continued to enlarge and metastasized to the lung and bone. The patient died 7 months after the biopsy. [Case 4] A 62-year-old woman under treatment for rheumatoid arthritis (RA) was found, on a chest X-ray, to have a right anterior mediastinal tumor. Histological diagnosis using the Chamberlain procedure suggested lymphoproliferative disorder, and the RA medication was discontinued. This was followed by a decrease in the tumor size and avoidance of invasive surgery. The patient remains well, 15 months after the biopsy. [Conclusion] The Chamberlain procedure proved useful for definitive diagnosis in all 4 cases of invasive anterior mediastinal tumors. We recommend the Chamberlain procedure for biopsy since it enables safe, rapid, and successful collection of tissue samples.

Primary MALT-type lymphoma of the thymus: a clinicopathological and immunohistochemical study of six cases

BACKGROUND

Six cases of primary extranodal marginal zone B-cell lymphoma of the thymus (MALT [mucosa-associated lymphoid tissue]) are described.

METHODS

The patients were all women between 48 and 59 years. Clinically, all patients, except for one, were Caucasians. Two patients had a history of autoimmune disease, while one was being investigated for such a possibility. The remaining three patients did not have a history of autoimmune disorders.

RESULTS

In those patients who had symptoms related to their anterior mediastinal masses, nonspecific symptoms, including shortness of breath and chest pain, predominated. Histologically, the tumors had the classical morphologic features of cystic and solid areas with an atypical monocytoid cellular proliferation. Immunohistochemical stains performed in all cases showed kappa monotypic expression and B-cell phenotype.

CONCLUSIONS

The current cases highlight that MALT lymphomas of the thymus can occur in a setting not related to autoimmune disease or in those not of Oriental ethnic background and that mediastinal cystic lesions require proper sampling in order to adequately evaluate the possibility of MALT lymphoma.

Mucosa associated lymphoid tissue (MALT) lymphoma of the thymus with trisomy 18

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) of the thymus is rare and little is known about its karyotype abnormality. MALT lymphoma in general shows a good prognosis, but some reports suggest that the presence of trisomy 18 predicts recurrence. Here, we report a patient with MALT lymphoma of the thymus and the left parotid gland accompanied by Sjogren's syndrome. The karyotype analysis revealed that this is the first case of thymic MALT lymphoma with trisomy 18, which we believe is worth reporting. We also review cases with thymic MALT lymphoma previously reported in the literature.

Thymic and pulmonary mucosa-associated lymphoid tissue lymphomas in a patient with Sjögren’s syndrome and literature review

Mucosa-associated lymphoid tissue lymphoma (MALToma) has been reported in several organs. Among MALTomas, thymic and pulmonary MALTomas are rare. The present report describes a patient with Sjögren's syndrome who presented thymic and pulmonary MALTomas. Although the exact pathogenetic relationship between these two tumours is uncertain, it is likely that the underlying immune dysregulation related to Sjögren's syndrome contributed to the occurrence and the unusual manifestation of MALTomas in this patient.

Micronodular thymoma: an epithelial tumour with abnormal chemokine expression setting the stage for lymphoma development

The aetiology of primary B-cell lymphomas of the thymus is enigmatic. Although thymic follicular lymphoid hyperplasia (TFH) is commonly associated with myasthenia gravis (MG), lymphoma is not a complication of this condition. The present paper reports a high frequency of monoclonal B-cell populations (6 of 18 cases; 33%) in micronodular thymoma (MNT), a peculiar thymic epithelial neoplasm with a B-cell-rich stroma, while B cells were consistently polyclonal in TFH (25 cases) and other types of thymomas (15 cases) (p < 0.001). An intratumoural lymphoma could be identified in three of the six monoclonal MNTs. Sequencing of the monoclonal IgH chain revealed partially overlapping VDJ gene usage in MNT and thymic mucosa-associated lymphoid tissue (MALT) lymphomas. The neoplastic epithelium of MNTs, but not of TFH and other types of thymoma, expressed high levels of dendritic cell, T-cell, and B-cell chemoattractants, such as CCL18, CCR6, and CCL20. It is concluded that abnormal chemokine expression in an epithelial tumour, MNT, can promote the recruitment of MALT, the emergence of monoclonal B cells, and, eventually, the subsequent development of mediastinal lymphomas. More generally, the concept that expression of a 'high-risk' spectrum of chemokines due to local or genetic factors may interfere with B-cell homeostasis and may contribute to MALT lymphoma development in chronic inflammatory states is proposed.

Extranodal Marginal Zone B-cell Lymphoma of Mucosa-associated Lymphoid Tissue (MALT Lymphoma) in the Thymus: Report of Four Cases

Mucosa-associated lymphoid tissue (MALT) lymphoma in the thymus is extremely rare, and little is known about its clinicopathological features. In this study, we examined four cases of MALT lymphoma in the thymus at our institute in terms of clinicopathological features. Most patients had autoimmune disease or hyperglobulinemia, and they also had cysts in the tumors. Both elevated serum levels of autoantibodies and the polyclonal increase in serum Ig remained almost unchanged after total thymectomy in all patients. We recommend that MALT lymphoma in the thymus should be considered in the differential diagnosis when a cystic thymic mass is found and if the patient is Asian and/or has autoimmune disease or hyperglobulinemia.

Mucosa-associated lymphoid tissue lymphoma of the thymus: a case report with no evidence of MALT1 rearrangement

We report a case of thymic mucosa-associated lymphoid tissue (MALT) lymphoma (TML) that presented as an asymptomatic mediastinal mass in a 40-year-old woman with a past history of Sjögren syndrome. This case had the characteristic clinical and pathological features of TML, as found in most of the 24 previously reported cases, i.e., autoimmune context, especially Sjögren syndrome, IgA secretion, large epithelial cysts, lymphoepithelial lesions involving residual Hassal's corpuscles, epithelial cysts, and a marked plasmacytic differentiation with IgA expression. Reverse-transcription polymerase chain reaction for t(11;18)(q21;q21) was negative, in agreement with recently published data. In this case, investigation for t(14;18)(q32;q21) using fluorescent in situ hybridization was also performed and supplied negative results. Neoplastic cells were negative for MAL, a marker of primary mediastinal large B cell lymphoma (PMBL). Altogether, these findings further support that among MALT lymphomas, TML have peculiar clinical and morphological characteristics and appear not to involve MALT1 rearrangement. They also suggest the absence of a relationship between TML and PMBL.

Extranodal lymphoma originating from mucosa-associated lymphoid tissue of the nasopharynx

Non-Hodgkin's lymphoma originating from mucosa-associated lymphoid tissue has been connected with autoimmune disease. These tumours often arise in gastric mucosa and are extremely rare in airway mucosa. Three cases of mucosa-associated lymphoid tissue lymphoma in the cavum have been reported in the literature. A 52-year-old male with rheumatoid arthritis presented with an 8-month history of nasal obstruction and recurrent nasal blood discharge. On physical examination a bulky mass was observed in the nasopharynx. CT demonstrated a soft tissue lesion in the nasopharynx without bone destruction. MRI showed a contrast-enhanced mass with extension to the left pterygoid muscle. Biopsy revealed a low-grade B-cell lymphoid tumour of the marginal zone. The patient received six cycles of cyclophosphamide, vincristine and prednisone with adriamycin treatment, together with intracranial methrotrexate as a prophylactic measure. After 48 months of follow-up there was no evidence of disease and a control MRI scan was normal. The prognosis of this type of tumour is unpredictable and there are too few cases to enable definitive conclusions to be drawn.

Primary thymic extranodal marginal-zone B-cell lymphoma of mucosa-associated lymphoid tissue type exhibits distinctive clinicopathological and molecular features

Extranodal marginal-zone B-cell lymphoma (MZBL) of mucosa-associated lymphoid tissue (MALT) arising in the thymus is rare, with the largest series in the literature including only three cases. In the present study, we investigated 15 cases of thymic MALT lymphoma to systematically characterize its clinical, histopathological, and molecular features. There was a marked female predilection (male:female = 1:4), with a mean age of 55 years at diagnosis. There was a strong association with autoimmune disease, especially Sjögren's syndrome. Histologically, the thymic lymphoma showed the characteristic morphological features of extranodal MZBL of MALT type. Cysts were common. Prominent lymphoepithelial lesions were formed by centrocyte-like cells infiltrating and expanding the Hassall's corpuscles and epithelium lining the cysts. Plasmacytic differentiation was apparent in all cases. Notably, 13 of 15 cases expressed immunoglobulin (Ig) A phenotype; IgA expression in thymic MALT lymphoma was in striking contrast with the IgM phenotype observed in most of the Sjögren's syndrome-associated MZBLs and MALT lymphomas at other sites. Epstein-Barr virus was absent, and API2-MALT1 gene fusion, a recently reported MALT lymphoma-specific gene abnormality, was not detected in any case. Although one patient died of disease 85 months after the diagnosis, other patients were alive with overall 3-year and 5-year survival rates being 89% and 83%, respectively. Among the 22 patients reported previously and in the present series, at least 17 patients (77%) were Asians. These data indicate that thymic MALT lymphoma may represent a distinct subgroup of MALT lymphoma characterized by apparent predilection for Asians, a strong association with autoimmune disease, frequent presence of cysts, consistent plasma cell differentiation, tumor cells expressing IgA phenotype, and consistent lack of API2-MALT1 gene fusion.

Primary marginal zone lymphoma of the thymus accompanied by chromosomal anomaly 46,X,dup(X)(p11p22)

We report a case of primary marginal zone lymphoma in the thymus of a 34-year-old woman. She was initially suspected of having a mediastinal plasmacytoma because of the presence of dominantly proliferating plasmacytic cells in a small fragment obtained by thoracoscopic biopsy, and an elevated level of serum monoclonal IgA. However, histology of the tissue obtained by a subsequent open surgical biopsy revealed diffuse proliferation of atypical monocytoid B-lymphocyte-like cells, which showed prominent plasmacytic differentiation and a close association with thymic epithelial cells consistent with the histology of a marginal zone lymphoma of the thymus. These lymphoma cells were positive for CD19, CD20, IgA, and kappa, and negative for CD5, CD10, and other T/NK-cell and myelomonocyte antigens. Both G-banded and spectral karyotyping analyses revealed the lymphoma cells carried a chromosomal anomaly, 46,X,dup(X)(p11p22). Although large cell type B-cell lymphoma in the thymus (mediastinal diffuse large B-cell lymphoma), which is categorized as a definite subtype in revised European-American classification of lymphoid neoplasms and the new World Health Organization classification, is not infrequent, primary marginal zone lymphoma of the thymus is extremely rare. To our knowledge, this is the first case report of primary marginal zone lymphoma of the thymus with a detailed chromosomal analysis.

Mucosa-associated lymphoid tissue of the thymus hyperplasia vs lymphoma

In the thymus, the relationship between lymphofollicular hyperplasia and mucosa-associated lymphoid tissue (MALT)-type lymphoma is uncertain. We analyzed 14 cases with a diagnosis of thymic follicular hyperplasia in patients with connective tissue disease (n = 2), myasthenia gravis (n = 11), or both (n = 1). In 11 cases, well-defined reactive lymphoid follicles were surrounded by a continuous layer of medullary epithelial cells. A polyclonal rearrangement of the immunoglobulin heavy chain gene (IgH) was observed. In 3 cases, ill-defined lymphoid follicles with sheets of centrocytic-like B cells disrupting the medullary cytokeratin epithelial network were observed on certain sections. These cells expressed the phenotypic features of memory B cells with CD20, CD79a, and bcl-2 positivity and CD5, CD10, CD23, and bcl-6 negativity, and a monoclonal rearrangement of the IgH gene was detected. Appropriate sampling, cytokeratin staining, and molecular analyses may help to identify early MALT-type lymphoma developing in the setting of thymic lymphofollicular hyperplasia.

Primary marginal zone lymphoma of the thymus

Primary low-grade B-cell lymphomas of the thymus are rare, with only 7 reported cases in the literature. We describe 3 cases of primary low-grade thymic lymphoma. All had histologic features of extranodal marginal zone lymphoma and were composed predominantly of small lymphocytes with variable components of monocytoid cells and plasma cells. Overt transformation to large cell lymphoma occurred in 1 case. The neoplastic cells were immunoreactive for the B-cell marker CD20 and were positive for bcl-2 in 2 cases. Two of 3 patients had a long-standing history of autoimmune disease. Based on these findings and those of previously reported cases, marginal zone lymphoma is the predominant type of low-grade thymic B-cell lymphoma. These tumors seem to be more common in patients with autoimmune disorders, and as observed with marginal zone lymphoma arising at other anatomic sites, they may undergo transformation to a higher grade lymphoma.

Coexisting thymic and gastric lymphomas of mucosa-associated lymphoid tissues in a patient with Sjögren syndrome

Lymphomas of mucosa-associated lymphoid tissues (MALTomas) arising from the thymus are extremely rare. In this case report, we describe a 36-year-old woman with an 11-year history of Sjögren syndrome who was found to have a thymic MALToma coexisting with a gastric MALToma. Both tumors shared similar histologic features, showing clusters of centrocytic-like B cells, lymphoepithelial lesions, and prominent plasmacytic differentiation. They also showed the following identical immunohistochemical features: CD20(+), IgA/lambda(+), CD5(-), and CD43(-). Molecular studies using polymerase chain reaction methods revealed monoclonal gene rearrangement of the immunoglobulin heavy chain in the gastric MALToma, but not in the thymic MALToma. The possible pathogenesis of this unusual case is discussed.