Objective:This study sought to examine the clinicopathological features of monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) and to discuss its differential diagnosis.Methods:A total of 36 MEITL cases, collected between June 2015 and January 2024 from the Fourth Affiliated Hospital of Soochow University and the First Affiliated Hospital, College of Medicine, Zhejiang University, were analyzed. Patients underwent immunohistochemistry, in situ hybridization for Epstein-Barr virus-encoded small RNA (EBER), and T-cell receptor (TCR) gene rearrangement testing. Clinical data, laboratory results, and follow-up information were collected for correlation analysis.Results:The cohort included 36 patients (20 males and 16 females) aged 17-76 years (median: 57 years). Tumors outside the intestine were observed in 22 cases (61%). A total of 32 patients (89%) underwent surgical intervention and/or chemotherapy, and one patient received auto-HSCT. The median follow-up duration was 11.5 months (range: 8-73 months), with a median overall survival of 6 months (range: 1-67 months) ; 34 patients died during the follow-up period. Morphologically, nine cases (25%) exhibited significant pleomorphism. Immunohistochemical analysis revealed that high expression levels of both P53 and c-Myc were correlated with atypical morphology ( P=0.003 and P=0.016, respectively). Notably, patients with high P53 expression had significantly shorter survival times than those with low P53 expression ( χ2=4.922, P=0.027), whereas survival did not differ significantly based on c-Myc expression levels ( χ2=0.034, P=0.854). Furthermore, a PD-L1 CPS score ≥10 was observed in 22 cases (68.8%). Scattered EBER positivity in background cells was identified in four cases. All tested cases (17/17, 100.0%) showed clonal TCR gene rearrangements. Conclusions:MEITL is a rare but highly aggressive lymphoma with distinct clinical and pathological features. A subset of cases may exhibit atypical morphological patterns, complicating the diagnostic process. Improving awareness of this neoplasm is helpful for early and precise diagnosis as well as the estabolishment of novel therapy regimen.

Objective:This study sought to examine the clinicopathological features of monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) and to discuss its differential diagnosis.Methods:A total of 36 MEITL cases, collected between June 2015 and January 2024 from the Fourth Affiliated Hospital of Soochow University and the First Affiliated Hospital, College of Medicine, Zhejiang University, were analyzed. Patients underwent immunohistochemistry, in situ hybridization for Epstein-Barr virus-encoded small RNA (EBER), and T-cell receptor (TCR) gene rearrangement testing. Clinical data, laboratory results, and follow-up information were collected for correlation analysis.Results:The cohort included 36 patients (20 males and 16 females) aged 17-76 years (median: 57 years). Tumors outside the intestine were observed in 22 cases (61%). A total of 32 patients (89%) underwent surgical intervention and/or chemotherapy, and one patient received auto-HSCT. The median follow-up duration was 11.5 months (range: 8-73 months), with a median overall survival of 6 months (range: 1-67 months) ; 34 patients died during the follow-up period. Morphologically, nine cases (25%) exhibited significant pleomorphism. Immunohistochemical analysis revealed that high expression levels of both P53 and c-Myc were correlated with atypical morphology ( P=0.003 and P=0.016, respectively). Notably, patients with high P53 expression had significantly shorter survival times than those with low P53 expression ( χ2=4.922, P=0.027), whereas survival did not differ significantly based on c-Myc expression levels ( χ2=0.034, P=0.854). Furthermore, a PD-L1 CPS score ≥10 was observed in 22 cases (68.8%). Scattered EBER positivity in background cells was identified in four cases. All tested cases (17/17, 100.0%) showed clonal TCR gene rearrangements. Conclusions:MEITL is a rare but highly aggressive lymphoma with distinct clinical and pathological features. A subset of cases may exhibit atypical morphological patterns, complicating the diagnostic process. Improving awareness of this neoplasm is helpful for early and precise diagnosis as well as the estabolishment of novel therapy regimen.

Purpose To investigate the clinical pathologic features of five SMARCA4-deficient non-small lung cancers(SMARCA4-dNSCLCs).Methods Five cases of SMARCA4-dNSCLC was underwent by HE,immunohistochemical staining,and molecular detection,analyzed their clinicopathological char-acteristics and reviewed relevant literatures.Results All 5 ca-ses were male,and mean age was 66 years.Five patients had a history of smoking,three patients were treated with cough and blood in sputum as the first symptom,one was treated with a history of pulmonary tuberculosis combined with limb mobility disorder,and one was diagnosed with pulmonary nodules by physical examination.Under microscopic observation,tumor cells were poorly differentiated,with solid nest sheet distribu-tion,some with glandular structure,tumor cells had abundant e-osinophilic or transparent cytoplasm,vacuolar nuclear chroma-tin,nucleoli was visible,and nuclear mitosis was common.In-flammatory cell infiltration and sheet of necrosis were seen in the stroma.Immunohistochemical staining showed 5/5 diffuse ex-pression of CK(AE1/AE3)and CK7,5/5 loss expression of BRG1,1/5 diffuse expression of p40 and CK5/6,and Ki67 proliferating index ranged from 20％to 90％.FISH tests showed that 4/4 SMARCA4 genes missed.Five patients were followed up for 2-15 months,3 patients died and 2 patients survived.Conclusions SMARCA4-dNSCLC can have extensive morphologi-cal features,high degree of malignancy,and complicated treat-ment.BRG1 deficiency is helpful for diagnosis.Deepening the understanding of SMARCA4-dNSCLC can help the clinical cor-rect choice of treatment strategies and accurately evaluate patient prognosis.