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We present a case of thoracic SMARCA4-deficient undifferentiated tumor that needed to be differentiated from malignant lymphoma owing to multiple lymph node swelling and marrow involvement. A 52-year-old man developed multiple lymphadenopathies along with anorexia, general fatigue, fever, and sweating 2 months prior to admission. 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) scan revealed a mass lesion on the right upper lung, generalized lymph node swelling, and bone metastasis, indicating the presence of suspicious lung cancer; therefore, he was referred to our hospital. Malignant lymphoma was suspected at the time of admission because of elevated levels of lactate dehydrogenase (11,977 U/l) and soluble interleukin 2 receptor (2,152 U/ml) as well as marrow infiltration of large abnormal cells. On day 11, the patient died from rapid respiratory failure. Histological and immunohistochemical features of the pleural effusion cell block led to the diagnosis of thoracic SMARCA4-deficient undifferentiated tumor. Thoracic SMARCA4-deficient undifferentiated tumor was recently introduced in the 2021 World Health Organization classification of lung tumors, with most patients being young adults with a history of heavy smoking and poor prognosis. Because of the multiple lymph node swelling and marrow involvement, this undifferentiated tumor should be distinguished from malignant lymphoma.

Myelodysplastic syndromes/myeloproliferative neoplasm (MDS/MPN) is a type of myeloid neoplasm where at least one hematopoietic lineage exhibiting cytopenia clinically coexists with other (s) exhibiting hypercytosis. There is ineffective erythropoiesis and bone marrow coexistence of at least one hematopoietic lineage morphologically characterized by dysplasia of blood cells and other (s) characterized by pronounced proliferation. At a molecular level, various abnormalities have been identified that overlap with related diseases, and a prerequisite for MDS/MPN diagnosis includes ruling out various hematopoietic tumors and reactive conditions. Therefore, a multilateral approach involving clinical findings, morphology, and molecular biology is needed. Herein, we introduce the pathological features of MDS/MPN and the relationship between molecular abnormalities and morphological characteristics.

We report a patient with hairy cell leukemia Japanese variant (HCL-Jv) that developed after radiotherapy for orbital adnexal MALT lymphoma. A 78-year-old man was diagnosed as having MALT lymphoma in the left conjunctiva in December 2003. The patient was treated by local radiotherapy and the tumor disappeared. Thereafter, he gradually developed leukocytosis and mild splenomegaly. In May 2009, the leukocyte count was 34,300 with 80% lymphoid cells. A diagnosis of HCL-Jv was made since the lymphoid cells showed a hairy morphology with round nuclei and indistinct nucleoli. These cells expressed CD11c, CD19, CD20, CD103 and showed weak reaction for tartrate-resistant acid phosphatase (TRAP). Bone marrow was infiltrated by atypical cells with an intrasinusoidal pattern. No treatment was needed as the patient was asymptomatic without anemia, thrombocytopenia or lymphadenopathy. Results of the immunoglobulin light chain expression and the heavy chain rearrangement in the tumor cells indicated that the two mature B-lymphoid neoplasms, MALT lymphoma and HCL-Jv, in this patient were derived from independent clones. This appears to be the first reported case of HCL-Jv associated with other lymphoid tumor. Further analysis is needed to clarify the risk of secondary malignancy in HCL-Jv.

A 62-year-old woman was admitted to our hospital because of gastric mucosal bleeding. Gastroendoscopy revealed a gastric tumor which was diagnosed from the biopsied specimen as diffuse large B-cell lymphoma (DLBCL). Lymphoma cells had infiltrated the bone marrow showed morphological features resembling Burkitt lymphoma (BL). Nearly 100% of the cells in the bone marrow were positive for MIB-1 immunostaining. The chromosomal study was normal. Surface marker analysis disclosed that the cells were positive for CD10, CD19, CD20 and CD25. As lymphoma cells had infiltrated the central nervous system, combined chemotherapy was performed accompanied with intrathecal administration of anticancer drugs. Although transient improvement was observed, the patient died of the advanced disease three months after admission. As we have shown here, there are some cases of DLBCL with immunohistochemical features resembling BL. Further consideration about the appropriate chemotherapy program for this type of disease might be necessary.

A 60-year-old female visited our hospital in May 2001 because of systemic lymphadenopathy. Her white blood cell count was 25,510/microliters with 93% of lymphocytes. Bone marrow aspiration revealed that 86% of nucleated cells were lymphocytes. Lymphocytes in the peripheral blood and bone marrow were positive for CD 5, 19, 20, and sIgx and negative for CD 23. FISH analysis detected the chimeric bcl 1/IgH fusion gene. Immunohistochemistry of a biopsied lymph node revealed that lymphoma cells were positive for cyclin D 1. Mantle cell lymphoma (MCL) was diagnosed at clinical stage IV A. Although a partial remission was obtained after CHOP plus rituximab therapy, the patient's disease recurred in March 2002 and she died in spite of salvage therapy including rituximab. Immunohistochemistry of the bone marrow cells after salvage rituximab therapy revealed that lymphoma cells were still positive for CD 5 and cyclin D 1, but negative for CD 20 and sIgx. We could not exactly determine how frequently CD 20 expression becomes negative in B-cell lymphomas after treatment with rituximab. We found only two reported cases that suggested rituximab down-regulated CD 20 expression in MCL. We herein describe a case of MCL with very notable clinical features.

A 61-year-old male visited his doctor in October 2000 because of a high fever. Laboratory examination revealed leukocytosis with blast-like cells and thrombocytopenia. He was referred and admitted to our hospital in November 2000. Although he had mild splenomegaly, he had no lymphadenopathy on the first admission. The white blood cell count was 10,520/microliter with 45% blast-like cells and the platelet count was 51 x 10(3)/microliters. Bone marrow aspiration revealed 82% blast-like cells, which were positive for CD5, CD10, CD13, CD19, and CD20. Immunohistochemistry of the bone marrow clot sections revealed blast-like cells were positive for CD5, but negative for TdT, CD23 and cyclin D1. We diagnosed the patient as having de novo CD5-positive diffuse large B-cell lymphoma (DLBCL) with leukemic dissemination. He obtained a complete remission after two courses of CHOP therapy. The third chemotherapy was postponed because of strangulation of the intestine. He relapsed and died in spite of the third chemotherapy. CD5-positive DLBCL is one of the established disease entities that requires an appropriate therapy regimen because it is characterized by elderly onset, extranodal involvement, and a poorer prognosis.