Primary Extranodal Marginal Zone B-cell Research Articles

Primary hepatic extranodal marginal zone B-cell mucosa-associated lymphoid tissue lymphoma treated by laparoscopic partial hepatectomy: a case report

BackgroundPrimary hepatic extranodal marginal zone B-cell mucosa-associated lymphoid tissue (MALT) lymphoma is very rare, so it is difficult to diagnose preoperatively. And there is no established treatment for hepatic MALT lymphoma. We report herein a case of primary hepatic MALT lymphoma treated by laparoscopic partial hepatectomy, and discuss the usefulness of laparoscopic hepatectomy for a rare liver tumor.Case presentationThis patient was a woman in her 60s, who was diagnosed preoperatively as having synchronous liver metastasis from sigmoid colon cancer; therefore, laparoscopic partial hepatectomy was performed. She had a good course after the operation and was discharged on postoperative day 12. However, she was diagnosed pathologically as having primary hepatic MALT lymphoma. A bone marrow biopsy was also performed, and then she was finally diagnosed as having limited-stage primary hepatic MALT lymphoma. She received no postoperative treatment and showed no recurrence for 4 years postoperatively.ConclusionsWe experienced the good result of the patient with limited-stage primary MALT lymphoma treated by laparoscopic partial hepatectomy. Liver tumors are sometimes misdiagnosed by imaging examinations alone. Laparoscopic hepatectomy has been widespread recently as a minimally invasive procedure, and it may be useful for both diagnosis and treatment.

IBCL-301 Primary Extranodal Marginal Zone B-Cell Lymphoma Located in the Lower Eyelid Case Treated With Rituximab

The majority of lymphoma cases are accompanied by painless enlargement of several cervical lymph nodes. However, its primary site may be also extranodal and unusual in some cases. Sharing an unusual case report of primary lower eyelid extranodal marginal zone B-cell Lymphoma treated with rituximab. A case report. In January 2021, a 53-year-old woman was admitted to our clinic with a subcutaneous change in her lower eyelid. The patient had a history of hypertension and had undergone IVF several years ago. There was a positive family history of cancer. There were no palpable lymph nodes in the periphery in physical examination. The hemogram and laboratory examinations were normal, as was the abdominal echo examination. An MRI scan of the cranium/orbits revealed the presence of a mass with a size of 15×8×13mm in the canthal angle/lower right cover OD, with no signs of intra-bulbar infiltration. A mass biopsy was performed, and the HP diagnosis revealed an extranodal marginal zone B-cell lymphoma (CD20+) (Bcl2+) (CD138+). Once the nature of the disease and the location of the mass had been determined, treatment with Rituximab 375mg/m2 every 28 days was planned. After 10 cycles of treatment, a PET-CT scan was performed, and a small region with low metabolic activity SUV max 3.0 was detected retrobulbar laterally on the right side. A cranial MRI scan revealed no evidence of recurrence or other pathological signs. The laboratory, abdominal, and neck echo exams were all normal. The patient's condition remains stable despite receiving rituximab 375 mg/m2 every two months, with no signs of disease and a normal MRI scan. The prognosis of this type of tumor is difficult to predict because the long-term response to the primary treatment must be closely monitored.

Poster: IBCL-301 Primary Extranodal Marginal Zone B-Cell Lymphoma Located in the Lower Eyelid Case Treated With Rituximab

Poster: IBCL-301 Primary Extranodal Marginal Zone B-Cell Lymphoma Located in the Lower Eyelid Case Treated With Rituximab

IBCL-309 Extranodal Marginal Zone B-Cell Lymphoma “Low Grade” Originating From Nasopharynx

Primary nasopharyngeal lymphoma is a very rare tumor with a variety of histopathologic subtypes, with only limited studies reported in literature. Sharing an unusual case report of primary nasopharynx extranodal marginal zone B-cell lymphoma, low-grade, as well as its diagnostic and therapeutic outcomes. A case report. A 46-year-old male was admitted to our clinic reporting nasal congestion and ear whistling. Negative history of any other chronic diseases or cancer. Physical examination revealed no pathological findings. The following were the laboratory findings: SE:4, WBC:6.3 103/mm3, Er:5.7 106/mm3, Hgb:14.6g/dl, Hct:48.6%, Plt:180×103/mm3, Mcv:85µm3, MCH:25.3pg, MCHC:29.3g/dL, Ret:3promil, and LDH:375U/l. The abdomen, axilla, and inguinal ultrasound scans were also normal, but the ultrasound scan of the neck revealed two hyperechoic nodules 23×24mm in the thyroid gland. On a CT scan of the paranasal spaces, maxillary sinusitis, nasal septum deviation, and polyposis in the nasopharynx were discovered and then a biopsy was performed on that site. The histopathology and immunohistochemistry diagnosis revealed a low-grade extranodal marginal zone B-cell lymphoma, positive on CD3, CD20, Bcl-2, CD10, Pax-5, CD23, MUM-1, CD138, and Ki-67:5 %. We decided to begin with chemotherapy rituximab, cyclophosphamide, hydroxydaunorubicin hydrochloride, vincristine, and prednisone (R-CHOP) protocol every 21 days. After four treatments, the CT scan revealed a free nasopharynx and a thyroid nodule that was partially shrunk, size 17×18mm, and then we decided to continue with four more R-CHOP treatments. A repeated CT scan revealed free paranasal spaces and in the ultrasound scan, there were still thyroid nodules 22×24mm. PET-CT examination revealed no pathological accumulations after a total of eight R-CHOP protocol treatments. For further examination, thyroid scintigraphy and cytological analysis-FNA were recommended. Thyroid hormones, anti-TPO, anti-TG, calcitonin, and CEA levels were in the norm. The patient is currently waiting for a thyroid nodule biopsy. 14 months after completing the R-CHOP treatment protocol, the patient is still in remission, with no signs of disease and a normal CT scan. This type of tumor's prognosis is difficult to predict, and there are far too few examples to draw firm conclusions.

A RARE PRESENTATION OF PRIMARY PULMONARY EXTRANODAL DIFFUSE LARGE B CELL LYMPHOMA

SESSION TITLE: Monday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Diffuse large B cell lymphoma (DLBL) is a common subtype of non-Hodgkin’s lymphoma (NHL) that usually presents with rapidly expanding lymphadenopathy. Here we present an unusual case of DLBL with a primary extra-nodal pulmonary presentation. CASE PRESENTATION: A 91-year-old female presented to her PMD for evaluation of a non-productive cough of several weeks’ duration. She had no prior history of pulmonary disease, was a never smoker, and was independent. She denied recent travel, pets, or known sick contacts and was up-to-date with pneumonia vaccinations. Complete blood counts and routine serum chemistries were unremarkable. She returned three months later with continued non-productive cough as well as generalized fatigue and intermittent chills. She was prescribed benzonatate and doxycycline for management of bronchitis. A CXR was ordered which showed a 4.5 cm right hilar opacity. CXR performed one year prior was unremarkable. She was referred for pulmonary consultation. CT chest showed a right upper lobe 4.8 x 5.9 cm mass, a left lower lobe 2.1 x 2.3 cm mass, right pleural thickening, and right cardiophrenic adenopathy measuring 2.0 x 1.2 cm. A navigational bronchoscopy with biopsy demonstrated a mass partially occluding right upper lobe bronchus and biopsy was consistent with DLBL. PET-CT revealed multiple areas of hypermetabolic activity in the abdomen, pelvis, and chest with multiple pulmonary masses, the most superior of which occluded the right upper lobe bronchus, as well as extensive pleural disease. She was started on a non-anthracycline chemotherapy regimen within two weeks of diagnosis. DISCUSSION: Primary NHL of the lung is rare, accounting for 0.4% of all malignant lymphomas. DLBL is an uncommon subtype within that group. Symptoms are non-specific, as are associated radiologic findings, making initial diagnosis difficult. Fine needle aspiration of DLBL usually obtains insufficient material to evaluate the architecture of the lymphoma for diagnosis. The majority of patients require invasive diagnostic biopsies to provide adequate tissue for evaluation. Several studies have shown that cell marker studies using bronchoalveolar lavage may be useful. Prompt initiation of treatment is necessary as DLBL of the lung has a worse prognosis than the more common MALT lymphoma of the lung. However, some studies report survival rates as high as 86% at three years for primary NHL of the lung. CONCLUSIONS: DLBL is a common NHL subtype that rarely manifests with primary pulmonary presentation masquerading as a primary lung malignancy. Given the non-specific clinical presentation, non-specific radiologic findings, and overall rarity, initial diagnosis is difficult, making prompt treatment a challenge. Further research is warranted to better diagnose and prognosticate primary DLBL of the lung. Reference #1: Teras, L. R., DeSantis, C. E., Cerhan, J. R., Morton, L. M., Jemal, A. and Flowers, C. R. (2016), 2016 US lymphoid malignancy statistics by World Health Organization subtypes. CA: A Cancer Journal for Clinicians, 66: 443-459. https://doi.org/10.3322/caac.21357 Reference #2: Kandori S, Kojima T, Nishiyama H. The updated points of TNM classification of urological cancers in the 8th edition of AJCC and UICC. Jpn J Clin Oncol. 2019; Reference #3: Kurtin PJ, Myers JL, Adlakha H, et al. Pathologic and clinical features of primary pulmonary extranodal marginal zone B-cell lymphoma of MALT type. Am J Surg Pathol. 2001;25(8):997-1008. DISCLOSURES: No relevant relationships by Joseph Berman, source=Web Response No relevant relationships by Miguel Conde, source=Web Response No relevant relationships by Kristin Fless, source=Web Response No relevant relationships by Vagram Ovnanian, source=Web Response No relevant relationships by Killol Patel, source=Web Response

Primary hepatic extranodal marginal zone B-cell lymphoma treated by surgical resection: A case report

Primary hepatic extranodal marginal zone B-cell lymphoma treated by surgical resection: A case report

Primary extranodal marginal zone B-cell lymphoma with AL amyloidosis in cerebral parenchyma in an immunocompetent patient

Herein reported is an extremely rare case of primary MALT lymphoma of cerebral parenchyma. A 79-year-old man presented with paresis. Imaging modalities identified a tumor measuring 3cm in diameter in right cerebral parenchyma. An operation completely resected the tumor. Macroscopically, the tumor was well defined, but showed mild infiltrative features. Histologically, the tumor showed proliferation of small atypical lymphocytes separated by fibrous septae with AL amyloid depositions. No apparent plasma cell differentiation was seen. The tumor cells showed monotonous appearances with hyperchromatic nuclei but without nucleoli and nuclear indentations. Immunoblastic cells were scattered. Immunohistochemically, tumor cells were positive for vimentin, CD45, CD20, CD79α, bcl-2, CD3 (focal), CD45RO (focal), CD5 (focal), CD10, CD23, bcl-6, CD138, p53, and Ki-67 (labeling=27%). The immunoblastic cells were positive for CD30. The lymphoid cells were negative for Epstein–Barr virus (EBV)-related molecules of EBV latent membrane protein-1 (LMP-1) and EBV early RNAs (EBER). They were also negative for cytokeratins AE 1/3 and CAM5.2, cyclin D1, CD34, GFAP, α-smooth muscle actin, and S100 protein. Because of the heterogeneity of tumor cells and positive AL amyloid deposition, the author diagnosed it as primary MALT lymphoma. The patient is now free from tumors. Differential diagnosis was discussed.

Primary extranodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue type in the central nervous system (MZL CNS) presented as traumatic subdural hematoma and subarachnoid bleeding – case report

The study describes a very rare case of primary extranodal marginal zone Bcell lymphoma of the central nervous system (MZL CNS) with an unusual clinical and radiological presentation mimicking subarachnoid bleeding and subdural hematoma (SDH) after head injury. The patient presented symptoms which had commenced 3 weeks earlier: a gradually-progressing headache associated with periodic right-sided cramp of the face muscles and numbness of the right upper limb. During urgent craniotomy for drainage of the presumed SDH, a tumor mass histopathologically and immunohistochemically matching marginal zone B-cell lymphoma was found. Molecular analysis confirmed monoclonal immunoglobulin heavy chain gene (IgH) rearrangement; the patient had previously suspected nodal lymphoma because of cervical lymphadenopathy, but histopathological, immunohistochemical and molecular examination excluded malignant lymphoma. The patient underwent successful radiotherapy, and achieved complete response. At present, no evidence of either systemic disease or lymph node enlargement has been found. The recognition of an indolent type of lymphoma in a rare anatomical localization is very important due to the proper management of the patient.

The Diagnosis and Management of Ocular Lymphoma

Lymphoma is the most common malignancy of the ocular adnexa. Most of the ocular adnexa lymphomas are non-Hodgkin B-cell lymphomas. The most common type of ocular adnexa lymphoma is primary extranodal marginal zone B-cell lymphoma of the MALT (mucosa-associated lymphoid tissue). Most of these neoplasms are primary extranodal lymphomas, although 10% to 32% are secondary tumors from disseminated disease. A 58-year-old woman presented for a comprehensive examination, with the chief complaint of ocular discomfort in both eyes. Anterior segment examination revealed bilateral salmon-colored lesions of the inferior and superior conjunctivae. The patient was referred for systemic evaluation and histopathology of the conjunctival lesions. She was diagnosed as having marginal zone lymphoma of the MALT and underwent radiation therapy (RT). Ocular lymphoma may present on routine examination or with mild symptoms. Although most commonly a primary extranodal neoplasm, the condition may be associated with disseminated lymphoma and requires thorough evaluation and staging of the disease for determination of appropriate treatment. The primary eye care provider plays an important role in the identification and staging of the disease, as well as managing complications from RT. It is also important to recognize that concurrent conditions requiring treatment with topical medications, such as glaucoma, may be complicated after treatment because of the inflammation and ocular surface irritation after RT. The necessity and benefit of the addition of intraocular pressure medications during that time should be measured on a case-by-case basis. Patients should be followed closely after treatment for relapse of disease and identification of complications from ocular RT.

A rare case of primary extranodal marginal zone B-cell lymphoma of the ovary, fallopian tube, and appendix in the setting of endometriosis

Extranodal marginal zone B-cell lymphomas are uncommon. Most occur in the gastrointestinal tract. Marginal zone B-cell lymphomas of the female genital tract are rare, and few cases exist of marginal zone B-cell lymphomas of the uterus, cervix, and fallopian tubes. We report the first marginal zone B-cell lymphoma of the ovary, fallopian tube, and appendix arising in endometriosis.

Clinicopathologic features of primary thymic extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue type

To study the clinicopathologic features of primary thymic extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT). The clinical and pathologic findings were evaluated in 3 cases of biopsy confirmed thymic MALT lymphoma. The clincopathologic features, treatment and prognosis were discussed and literatures reviewed. One male and two female patients presented with asymptomatic mediastinal masses with a history of Sjögren syndrome. They were aged 36, 35 and 41 years respectively, and only one patient had B symptoms. Grossly, all three tumors were encapsulated and had multiple variable-sized cysts on cut-surface. Histopathologically, the normal thymic lobular architecture was effaced by abnormal dense lymphoid infiltration. Prominent lymphoepithelial lesions were formed by centrocyte-like cells infiltrating and expanding Hassall's corpuscles and epithelial cyst lining. All cases showed apparent plasmacytic differentiation. Immunohistochemically, the tumor cells were positive for CD20, CD79a, bcl-2 and negative for CD3, CD5, cyclin D1, CD43, CD10, bcl-6, and CD23. The plasma cells showed kappa light chain restriction. Immunoglobulin heavy chain rearrangement in three cases was confirmed by PCR. All patients were at early stage and received routine chemotherapy with or without radiotherapy after surgical removal. All patients achieved complete remission with 24, 18 and 3 months follow-up, respectively. Primary thymic MALT lymphoma may be a rare distinctive lymphoma. It can be diagnosed by HE and immunohistochemical study and should be differentiated from reactive lymphoid proliferation, other types of lymphoma and mediastinal thymoma.

Primary extranodal marginal zone B-cell lymphoma of hard palate: A case report

Introduction: MALT (mucosa associated lymphoid tissue) lymphomas comprise a heterogeneous group, originally thought to be derived from the marginal zone B­cells that are found surrounding B­cell follicles and within the adjacent lymphoepithelium. They arise most commonly in extranodal organs such as the stomach, major salivary glands and thyroid. Thus, they can be precisely described as extranodal marginal zone B­cell lymphomas (ENMZL). Here, we report a case of MALT lymphoma arising in the palatal minor salivary glands. Case Report: A 55­year­old woman presented with two years history of a left posterior palatal mass. Clinical investigations of the case included computed tomography (CT) scan for the assessment of bone destruction and possible intra­maxillary extension. Histopathological features and immunohistochemistry findings were consistent with the diagnosis of extranodal marginal zone B­cell lymphoma of MALT type. The lesion was treated by complete surgical excision and followed for two years. Conclusion: Even though oral localization of ENMZL is rare, it should be included in the differential diagnosis of benign­ appearing swellings of oral cavity.

Primary extranodal marginal zone B-cell lymphoma of MALT-type involving the fallopian tube

► We experience one case of MZBL of MALT type in the fallopian tube. ► There was no remarkable inflammatory or infection sign. ► We report this case with a review of related literature.

Primary MALT-type Lymphoma of the Thymus: A Clinicopathological and Immunohistochemical Study of Six Cases

Six cases of primary extranodal marginal zone B-cell lymphoma of the thymus (MALT [mucosa-associated lymphoid tissue]) are described. The patients were all women between 48 and 59years. 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. 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. 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.

Thymic extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue: a clinicopathological and genetic analysis of six cases

We investigated six new cases of primary thymic extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) to further characterize the clinicopathological and genetic features. The male to female ratio was 1:1. One female patient had suffered from systemic lupus erythematosus. Another female patient was diagnosed with rheumatoid arthritis after thymectomy. One patient had a concurrent tumor in the eyelid. Radiologically, all tumors were located in the prevascular space and presented as asymmetric heterogeneously enhanced cystic and solid masses. MALT1, BCL10 or IGH translocations and trisomy 18 were not observed in any cases by fluorescence in situ hybridization (FISH) analysis. Trisomy 3 was detected in one patient and another showed a TNFAIP3/A20 deletion. Meta-analysis (n = 51) including the present and previously reported cases revealed that the prevalence of autoimmunity was much lower in males with thymic MALT lymphoma compared to females (33% vs. 87%, p = 0.001). Additionally, the average age of females or patients with autoimmunity was about 10 years younger than that of males or patients without autoimmunity (p = 0.003 and p = 0.008, respectively). In summary, thymic MALT lymphoma arising without underlying autoimmunity frequently involves males or older patients. Trisomy 3 and an A20 deletion might play a role in the pathogenesis of thymic MALT lymphoma.

Subcutaneous ‘lipoma-like’ B-cell lymphoma associated with HCV infection: a new presentation of primary extranodal marginal zone B-cell lymphoma of MALT

BackgroundHepatitis C virus (HCV) infection has been linked to lymphoproliferative disorders. Marginal zone B-cell lymphoma (MZL) represents one of the most frequent lymphoma subtypes associated with HCV infection. We describe an unusual subset of HCV-associated MZL characterized by subcutaneous presentation. Materials and methodsA series of 12 HCV-positive patients presenting with subcutaneous nodules that revealed lymphoma infiltration at biopsy. Molecular analysis of immunoglobulin heavy chain (IGH) gene rearrangement and FISH investigations for t(11;18)(q21;q21) and t(14;18)(q32;q21) were carried out in nine patients. ResultsThe 12 patients (median age 69.5 years), all with positive HCV serology, presented with single or multiple subcutaneous nodules resembling lipomas. Histologically the lesions showed lymphoid infiltrates, consistent with extranodal MZL of mucosa-associated lymphoid tissue (MALT). Functional IGH gene rearrangements were identified in nine tested patients, with somatic mutations in 82%, indicating a histogenesis from germinal center-experienced B cells. The t(11;18) was found in two of nine cases. Staging did not show any other lymphoma localization. In two patients, a response was achieved with antiviral treatment. Extracutaneous spread to MALT sites occurred in a case. ConclusionsOur observations expand the spectrum of HCV-associated lymphomas to include a subset of extranodal MZL characterized by a novel primary ‘lipoma-like’ subcutaneous presentation and indolent clinical course.

A minute focus of extranodal marginal zone B-cell lymphoma arising in Hashimoto thyroiditis diagnosed with PCR after laser capture microdissection: a case report

BackgroundPrimary thyroid gland lymphomas are uncommon tumours that occur in the setting of lymphocytic thyroiditis or Hashimoto's disease in almost all cases. In this condition a distinction between an inflammatory lymphoid infiltrate and a low grade lymphoma may be extremely difficult and precise criteria are necessary for a correct diagnosis.Patient and methodsWe report a case of a minute focus of primary extranodal marginal zone B-cell lymphoma (EMZBCL), incidentally discovered in a 63-year-old man with Hashimoto thyroiditis (HT) and diagnosed by means of polymerase chain reaction (PCR) after laser capture microdissection.The histological examination of surgical specimen confirmed the diagnosis of HT and showed a minute focus of dense lymphoid infiltrate (less than 4 mm in diameter), composed by centrocyte-like cells forming MALT balls. Immunoistochemistry was not useful. A microscopic focus of EMZBCL was suspected on the basis of morphological features. PCR assays revealed the rearrangement of the heavy chain of immunoglobulins only in the microdissected suspicious area, confirming the diagnosis of EMZBCL.ConclusionOur finding suggests that in cases of autoimmune thyroiditis a careful examination of the thyroid specimen is warranted, in order to disclose areas or small foci of lymphomatous transformation. Furthermore, in difficult cases with doubtful immunohistological findings, ancillary techniques, such as molecular studies, are necessary for a conclusive diagnosis.

Primary Extranodal Marginal Zone B-cell Lymphoma of the Female Genital Tract

Primary extranodal marginal zone B-cell lymphoma (EMZL) of the female genital tract is a clinical indolent disease. A 61-year-old woman presenting with vaginal prolapse underwent a vaginal hysterectomy and anterior colporrhaphy. Histological examination of the uterus revealed lymphocytic infiltration of the endometrium. The immunohistochemical profile was not in accordance with any known reactive lymphocytic proliferation. Additional polymerase chain reaction and fluorescence in situ hybridization established the diagnosis of EMZL. After staging workup, it was classified as Ann-Arbor stage 1E. Therefore, no adjuvant therapy was needed. Incidental finding of EMZL in the endometrium is exceptional. The asymptomatic presentation is according to the indolent character of extranodal marginal zone lymphoma.

Chromosome instability and translocation t(11;18) in primary gastric marginal zone B‐cell lymphoma of MALT‐type

The prognosis for patients with mucosa-associated lymphoid tissue (MALT) lymphomas is good; these tumours have usually an indolent course with overall survival rates that are greater than 80% at 5-year, but some rare cases with histological transformation in aggressive diffuse large cell lymphoma have also been diagnosed. Here, we present cytogenetic results on endoscopic bioptic material of 42 cases of primary gastric extranodal marginal zone B-cell lymphoma (EMZL) using fluorescence in situ hybridization (FISH) approach with API2, MALT1 and centromeric probes for chromosome 3 and 18, and their impact on the clinical outcome.

The Incidence and Anatomic Site Specificity of Chromosomal Translocations in Primary Extranodal Marginal Zone B-cell Lymphoma of Mucosa-associated Lymphoid Tissue (MALT Lymphoma) in North America

Several balanced translocations have been identified in extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) but there are few data regarding their frequency in different anatomic sites or the frequency of translocations involving BCL6 or kappa or lambda immunoglobulin light chain genes (IGK or IGL), particularly in patients from geographic regions other than Europe and Japan. One hundred thirty-three paraffin-embedded North American primary MALT lymphoma specimens from diverse anatomic sites were studied by fluorescence in situ hybridization (FISH) using probes for API2-MALT1, IGH-MALT1, IGH-BCL10, IGH-FOXP1, IGH, +/- centromeres 3, 7, 12, and 18, and a subset (n=74) were analyzed using FISH probes for IGK, IGL, and BCL6. Translocations were mutually exclusive and were detected in 26% of cases (17% API2-MALT1, 5% IGH-MALT1, 3% IGH-unknown translocation partner, and 1% IGH-BCL10). Aneuploidy was associated with IGH-MALT1 and IGH-BCL10 but only rarely with API2-MALT1. There was striking site specificity, with API2-MALT1 showing a marked predilection for lung and intestine, and IGH-MALT1 and IGH-BCL10 occurring almost exclusively in lung. Twenty-three percent of translocation-negative primary MALT lymphomas from diverse sites showed complete/partial trisomy 18. No MALT lymphomas with translocations involving IGK, IGL, BCL6, or FOXP1 were identified. This FISH panel detected cytogenetic abnormalities in half of all MALT lymphomas, and translocations arose preferentially in MALT lymphomas of the lung and gastrointestinal tract. Differences in incidence and anatomic site specificity of translocations between North American and non-North American cases may reflect geographic variability of infectious or other etiologic factors.