High serum proteinase-3 levels predict poor progression-free survival and lower efficacy of bevacizumab in metastatic colorectal cancer.

BACKGROUND: To improve the prognosis of patients with metastatic colorectal cancer (mCRC), investigating predictive biomarkers of their prognosis and chemotherapeutic responsiveness is necessary. This study aimed to analyze the clinical significance of serum proteinase-3 (PRTN3) as a predictor for prognosis and chemosensitivity, especially to bevacizumab therapy, in mCRC. METHODS: This single-center retrospective observational study enrolled 79 patients with mCRC in our hospital and 353 patients with colorectal cancer in the TCGA database. Preoperative serum PRTN3 levels were measured using an enzyme-linked immunosorbent assay. The clinicopathological characteristics and prognosis according to serum PRTN3 levels were then evaluated. PRTN3 expression in tumor and stromal cells was evaluated immunohistochemically. The impact of PRTN3 levels on angiogenesis and bevacizumab sensitivity was evaluated using the tube formation assay. RESULTS: Serum PRTN3 levels were an independent poor prognostic factor for progression-free survival (PFS) (hazard ratio, 2.082; 95% confidence interval, 1.118-3.647; P=0.010) in patients with mCRC. Similarly, prognostic analysis with TCGA data sets showed poorer overall survival in patients with PRTN3 expression than that in patients without PRTN3 expression, especially in patients with stage IV. Immunohistochemical analysis of resected specimens revealed that stromal neutrophils expressed PRTN3, and their expression level was significantly correlated with serum PRTN3 levels. Interestingly, the effectiveness of first-line chemotherapy was significantly poorer in the high serum PRTN3 level group. High serum PRTN3 was significantly associated with poor PFS (hazard ratio, 3.027; 95% confidence interval, 1.175-7.793; P=0.0161) in patients treated with bevacizumab, an anti-angiogenic inhibitor. The tube formation assay revealed that PRTN3 administration notably augmented angiogenesis while simultaneously attenuating the anti-angiogenic influence exerted by bevacizumab therapy. CONCLUSIONS: Serum PRTN3 levels could be a novel predictive biomarker of PFS of first-line chemotherapy, especially for bevacizumab therapy, in patients with mCRC.

IL-6 Levels Correlate with Prognosis and Immunosuppressive Stromal Cells in Patients with Colorectal Cancer.

BACKGROUND: The prognosis for patients with colorectal cancer (CRC) is determined by tumor characteristics as well as the host immune response. This study investigated the relationship between an immunosuppressive state and patient prognosis by evaluating the systemic and tumor microenvironment (TME) interleukin (IL)-6 levels. METHODS: Preoperative serum IL-6 levels were measured using an electrochemiluminescence assay. Expression of IL-6 in tumor and stromal cells was evaluated immunohistochemically in 209 patients with resected CRC. Single-cell analysis of tumor-infiltrating immune cells was performed using mass cytometry in 10 additional cases. RESULTS: Elevated serum IL-6 levels were associated with elevated stromal IL-6 levels and a poor prognosis for patients with CRC. High IL-6 expression in stromal cells was associated with low-density subsets of CD3+ and CD4+ T cells as well as FOXP3+ cells. Mass cytometry analysis showed that IL-6+ cells among tumor-infiltrating immune cells were composed primarily of myeloid cells and rarely of lymphoid cells. In the high-IL-6-expression group, the percentages of myeloid-derived suppressor cells (MDSCs) and CD4+FOXP3highCD45RA- effector regulatory T cells (eTreg) were significantly higher than in the low-IL-6-expression group. Furthermore, the proportion of IL-10+ cells in MDSCs and that of IL-10+ or CTLA-4+ cells in eTregs correlated with IL-6 levels. CONCLUSION: Elevated serum IL-6 levels were associated with stromal IL-6 levels in CRC. High IL-6 expression in tumor-infiltrating immune cells also was associated with accumulation of immunosuppressive cells in the TME.

Double cancer of primary hepatic angiosarcoma and hepatocellular carcinoma treated with atezolizumab plus bevacizumab.

AIM: Primary hepatic angiosarcoma (PHA) is extremely rare, and its imaging findings are similar to those of other liver tumors including hepatocellular carcinoma (HCC). Here, we report a case of hepatitis C virus (HCV)-related HCC followed by PHA that showed remarkable clinical response to atezolizumab plus bevacizumab (Atezo/Bev) therapy. CASE PRESENTATION: A 78-year-old man with recurrent HCC had a liver tumor with lymphadenopathy. Although considered as HCC recurrence, microscopic examination of the resected liver and lymph node showed PHA. Three months later, a solitary lung nodule was newly detected and subsequently resected. The pathological diagnosis was poorly differentiated HCC. Therefore, the patient was finally diagnosed with double cancer of PHA and HCC. Thereafter, he developed a new liver tumor with lymphadenopathy and received Atezo/Bev therapy. Liver tumor biopsy was carried out before the treatment. The pathological diagnosis was angiosarcoma. The patient showed a partial response after two courses of Atezo/Bev therapy. CONCLUSION: To our best knowledge, this report is the first case to present HCV-related HCC followed by PHA and to show that Atezo/Bev therapy is beneficial for PHA.

[Subcutaneous Bronchogenic Cyst in the Anterior Chest Diagnosed before Coronary Artery Bypass Grafting:Report of a Case].

A 65-year-old woman was transported to our hospital by ambulance because of severe dyspnea. She had had a subcutaneous tumor on her anterior chest since her childhood. Coronary angiography revealed three vessel disease with significant stenosis in the left main trunk. Excision of anterior chest tumor, 70×60×50 mm in size, was performed before coronary artery bypass grafting( CABG). It was a unilocular cyst adhering to the sternum, and was composed of ciliated epitheliums, goblet cells and smooth muscle cells. Based upon the existence of smooth muscle cells, the tumor was diagnosed as bronchogenic cyst. CABG was performed through mid-sternum about two months after the tumor excision, and the postoperative course was uneventful.

[A Case in Which FOLFOXIRI Was Useful as Preoperative Chemotherapy for Locally Advanced Rectal Cancer with Difficulty in Securing CRM].

The patient is a 65-year-old woman. Colonoscopy performed for close examination of constipation and lower abdominal pain revealed a circumferential type 3 lesion in the rectum Ra. A CT scan showed invasion of the primary lesion into the extramural and sacral front and multiple metastases in the mesorectal lymph nodes but no distant metastasis. Staging laparoscopy was performed. As the mesorectum around the primary lesion was tightly adherent, it was difficult to R0 resection; hence, only construction of colostomy was performed. We have introduced chemotherapy(FOLFOXIRI plus bevacizumab therapy), and 4 courses were administered. Post-treatment CT scan showed that the peri-invasiveness of the primary tumor had disappeared and the enlarged lymph nodes had shrunk. Furthermore, SUVmax of PET-CT for main lesion was decreased, dramatically. On day 109 after the initial surgery, laparoscopic low anterior resection was performed. Although the left hypogastric nerve was resected, other areas could be dissected and R0 resection could be performed. FOLFOXIRI therapy has shown good early-tumor shrinkage and depth of response and may be useful for patients with locally advanced rectal cancer who have difficulty securing circumferential resection margin(CRM).

Hepatic artery resection and reconstruction using the right gastroepiploic artery during pancreaticoduodenectomy in advanced pancreatic cancer.

PURPOSE: Surgical resection is the only curative treatment for pancreatic cancer. Arterial resection and reconstruction during pancreaticoduodenectomy for advanced pancreatic cancer remain controversial due to a high rate of complications. METHODS: We report two cases of pancreatic cancer with hepatic artery resection and reconstruction using the right gastroepiploic artery during pancreaticoduodenectomy after neoadjuvant therapy. RESULTS: The patients underwent pancreaticoduodenectomy with resection of the right hepatic and common hepatic arteries. Achieving direct anastomosis was difficult; therefore, we planned hepatic artery reconstruction using the right gastroepiploic artery. We performed the reconstruction using an interrupted suture with end-to-end anastomosis. The first patient developed a postoperative pancreatic fistula, while the postoperative course of the second patient was uneventful. However, there were no adverse events related to the arterial reconstruction. R0 resection was achieved, and postoperative computed tomography revealed good patency of the reconstructed artery. CONCLUSION: Hepatic artery reconstruction using the right gastroepiploic artery in pancreatic cancer might be technically safe and might become one of the alternative options.

A novel age-related venous amyloidosis derived from EGF-containing fibulin-like extracellular matrix protein 1.

Most intractable tissue-degenerative disorders share a common pathogenic condition, so-called proteinopathy. Amyloid-related disorders are the most common proteinopathies and are characterized by amyloid fibril deposits in the brain or other organs. Aging is generally associated with the development of these amyloid-related disorders, but we still do not fully understand how functional proteins become pathogenic amyloid deposits during the human aging process. We identified a novel amyloidogenic protein, named epidermal growth factor-containing fibulin-like extracellular matrix protein 1 (EFEMP1), in massive venous amyloid deposits in specimens that we obtained from an autopsied patient who died of gastrointestinal bleeding. Our postmortem analyses of additional patients indicate that EFEMP1 amyloid deposits frequently developed in systemic venous walls of elderly people. EFEMP1 was highly expressed in veins, and aging enhanced venous EFEMP1 expression. In addition, biochemical analyses indicated that these venous amyloid deposits consisted of C-terminal regions of EFEMP1. In vitro studies showed that C-terminal regions formed amyloid fibrils, which inhibited venous tube formation and cell viability. EFEMP1 thus caused a novel age-related venous amyloid-related disorder frequently found in the elderly population. Understanding EFEMP1 amyloid formation provides new insights into amyloid-related disorders occurring during the aging process. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Human amyloidosis, still intractable but becoming curable: The essential role of pathological diagnosis in the selection of type-specific therapeutics.

The molecular pathogenesis of human amyloidosis has been elucidated greatly during the last 20 years. Based on the understanding of the molecular mechanisms of amyloid fibril formation and deposition, various kinds of new drugs and therapeutics have been emerging to improve the prognosis of amyloidosis and even cure this disease. In this review article, we first summarize the pathogenesis and state-of-the-art therapeutics of representative types of systemic human amyloidosis, that is, immunoglobulin light chain-related, transthyretin-related, amyloid A-associated and ß2 -microglobulin-related amyloidosis. Next, we describe the essential roles of pathological diagnosis, especially the typing diagnosis of amyloidosis to appropriately guide type-specific therapies of amyloidosis patients. Finally, we introduce the activities of the government-funded group for surveys and research of amyloidosis in Japan, especially the nation-wide pathology consultation system of amyloidosis, which started in April 2018. The nation-wide improvement of the typing diagnosis of amyloidosis is essential for the appropriate treatment and care of amyloidosis patients in Japan.

Serum LOX-1 is a novel prognostic biomarker of colorectal cancer.

BACKGROUND: Colorectal cancer is the third most common cancer worldwide. If biomarkers can be identified in liquid biopsy, diagnosis and treatment can be optimized even when cancerous tissues are not available. The purpose of this study was to identify proteins from liquid biopsy that would be useful as markers of poor prognosis. METHODS: First, we comprehensively analyzed serum proteins to identify potential biomarkers and focused on serum lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1). The relationship between LOX-1 and the prognosis of patients with colorectal cancer has not been reported. Next, we validated this marker using serum samples from 238 patients with colorectal cancer by ELISA and 100 tissue samples by immunohistochemical staining. RESULTS: The optimal cut-off value of serum LOX-1 was 538.7 pg/mL according to time-dependent receiver operating characteristics curve analysis. The overall survival of patients with high levels of serum LOX-1 was significantly poorer than that of individuals with low levels of LOX-1 in the training and test datasets. In multivariate analysis for overall survival, serum LOX-1 was an independent prognostic factor identified in liquid biopsy (hazard ratio = 1.729, p = 0.027). The prognosis of patients with high LOX-1 expression in tumor tissues was significantly poorer than that of individuals with low expression (p =0.047 ). Additionally, inflammatory factors such as white blood cell count, C-reactive protein level, neutrophil/lymphocyte ratio, and monocyte/lymphocyte ratio were significantly higher in the group with high serum LOX-1 levels. CONCLUSIONS: Serum LOX-1 might be a useful biomarker of poor prognosis in colorectal cancer.

Purpuric drug eruption without leukocytoclastic vasculitis associated with vancomycin.

Vancomycin (VCM) has been reported to elicit adverse cutaneous drug reactions. However, VCM-associated purpuric drug eruption has not been reported yet, except leukocytoclastic vasculitis. A 16-year-old Japanese girl was admitted with a respiratory infection. We initiated intravenous administration of VCM. After the start of treatment, impalpable purpuric eruption appeared on her trunk. The eruption gradually extended to her neck, legs, and arms. Skin biopsy showed vasculitis with lymphocyte infiltration in the superficial dermis. A drug lymphocyte stimulation test yielded positive results for VCM. Her cutaneous symptoms rapidly reversed after the withdrawal of VCM. To the best of our knowledge, this is the first reported case of VCM-associated purpuric drug eruption, which differs from leukocytoclastic vasculitis. We recommend that VCM-associated purpuric drug eruption should be considered in the differential diagnosis during the administration of VCM, and a drug lymphocyte stimulation test may be useful for assessment of pathogenesis.

Impact of divergent differentiation in urothelial carcinoma on oncological outcome in patients with T1 high-grade bladder cancer.

OBJECTIVE: T1 high-grade bladder cancer has a poor prognosis compared with other non-muscle-invasive bladder cancers. We investigated the clinical outcomes among patients with T1 high-grade bladder cancer to identify factors related to cancer recurrence and disease progression. METHODS: We retrospectively reviewed the data of 148 patients who were diagnosed with T1 high-grade bladder cancer by transurethral resection from January 2001 to February 2015 at our institution. Clinicopathological factors were analyzed using univariate and multivariate analyses. RESULTS: The median age and follow-up duration were 72 years and 45.4 months, respectively. Sixty-two patients (41.9%) had recurrence, 28 (18.9%) experienced progression and 13 (8.8%) died of bladder cancer. In the multivariate analysis, divergent differentiation was an independent factor related to recurrence (P = 0.0096, hazard ratio = 2.5), whereas a non-papillary tumor shape, divergent differentiation and presence of a residual tumor at the time of the second transurethral resection were independent factors related to progression (P = 0.0349, hazard ratio = 3.8; P = 0.0074, hazard ratio = 6.8 and P = 0.0449, hazard ratio = 4.1, respectively). There were no independent factors related to cancer-specific mortality. Divergent differentiation was the only independent factor associated with both recurrence and progression. In addition, patients with divergent differentiation had significantly worse recurrence-free survival and progression-free survival rates than did patients without divergent differentiation (log-rank P = 0.0009 and P = 0.0019, respectively). CONCLUSIONS: In this study, the presence of divergent differentiation was related to worse oncological outcomes in patients with T1 high-grade bladder cancer. Patients with divergent differentiation may require stringent follow-up and early cystectomy after recurrence to improve oncological outcomes.

[A Case of Intrahepatic Cholangiocarcinoma with Ductal Plate Malformation Pattern].

A 56-year-old man with HCV infection was referred to our hospital for further evaluation and treatment of hepatic tumor. Abdominal enhanced computed tomography demonstrated an S8 hepatic tumor, about 15mm in maximal diameter. The tumor showed enhancement on the arterial phase and washout on equilibrium phase. EOB-MRI scan also showed the hepatic tumor with enhancement in the early phase and washout in the delayed phase. Liver function was normal. Serum AFP and PIVKA- II were normal and CEA and CA19-9 were elevated. However, no other tumor was detected by the colonoscopy, esophagogastroduodenoscopy and PET-CT. Under the diagnosis of HCC, partial hepatectomy was performed. Histologically, the tumor was composed of neoplastic glands with irregularly dilated lumen of adenocarcinoma, resembling ductal plate malformation(DPM). And Von Meyenburg complexes and foci of ordinary intrahepatic cholangiocarcinoma(ICC)were also found. ICC with this histologic features reported as a new subtype of ICCs.

Surgery for undiagnosed ground glass pulmonary nodules: decision making using serial computed tomography.

BACKGROUND: Although long-term observation of ground glass nodules on computed tomography facilitates the ability to distinguish malignant lesions from benign lesions, the resulting treatment delay can increase the rate of cancer recurrence. We reviewed our surgical cases of pathologically undiagnosed lung nodules possessing ground glass to clarify the clinical impact of selecting surgical candidates based on serial computed tomography, not preoperative biopsy results. METHODS: A consecutive series of 100 patients with clinically suspected lung cancer possessing ground glass among our prospective database of 262 surgical cases of suspected lung cancer were retrospectively reviewed. RESULTS: Surgical indication was determined based on the interval change in the outer diameter or internal attenuation of the lesions in 53 patients (increasing lesions), while that was determined based on the specific marginal or internal features of the lesions in 47 patients (non-increasing lesions). The length of preoperative follow-up was significantly longer in the patients with increasing lesions than in the patients with non-increasing lesions (27 vs. 3 months, P < 0.001). The final pathological diagnoses consisted of 97 adenocarcinomas and three non-malignant lesions. All increasing lesions were adenocarcinomas. Surgical biopsy contributed in avoiding futile lobectomy in patients with non-malignant lesions, while that caused false-negative result in one patient with an increasing lesion. Postoperative recurrence occurred in two patients. CONCLUSIONS: In a surgical series, serial computed tomography-diagnosed ground glass lesions are highly suggestive of adenocarcinoma, especially increasing lesions. Despite spending a long-term preoperative follow-up period without a pathological diagnosis, the surgical outcome is satisfactory. Surgical biopsy for increasing lesions is generally futile.

Atypical extraventricular neurocytoma in a 3-year-old girl: case report with radiological-pathological correlation.

BACKGROUND: Extraventricular neurocytoma (EVN) is a rare neuronal tumor histologically similar to central neurocytoma but arising in the brain parenchyma outside the ventricles. The minority of EVNs show atypical features including increased proliferative index, microvascular proliferation, or necrosis, and are called atypical EVN. Most of atypical EVNs occur in adults, and the tumors in children are extremely rare. A radiological-pathological correlation and radiological clue to atypical EVNs have not been clarified. CASE REPORT: We report a case of atypical EVN in a 3-year-old girl. Magnetic resonance imaging (MRI) revealed an extraventricular intraparenchymal tumor in the left frontal lobe, which was composed of homogeneous well-demarcated cystic component and peripheral ill-delineated solid component with enhancement. Angiography demonstrated vascular proliferation and arteriovenous shunting in the tumor. Histologically, the resected tumor was diagnosed as atypical EVN. Types of the tumor borders (well-circumscribed or infiltrative) and MRI findings correlated closely. Morphology of the tumor vasculature was remarkable for microvascular proliferation and dilated, thickened veins, which corresponded to the angiographic features. CONCLUSION: Although rare, atypical EVN should be included in the differential diagnosis of a cystic mass in the cerebral hemispheres in children. Radiological evaluation of tumor borders and angiographic characteristics might be useful for predicting atypicality of the tumor.

Efficacy of Enfortumab Vedotin After Chemotherapy With Anti-programmed Death-Ligand 1 (PD-L1) Maintenance Treatment in a Clear Cell Variant of Invasive Urothelial Carcinoma of the Renal Pelvis: A Case Report.

Among upper urinary tract urothelial carcinoma (UUTUC) cases, there are few reports of the clear cell variant. Systemic chemotherapy will be given according to the usual treatment for urothelial cancer unless lymph nodes or organ metastases make surgical treatment inappropriate. Here, we report a clear cell variant of UUTUC of the left renal pelvis with aortic lymph node metastasis. The patient in this case was treated with systemic chemotherapy, anti-programmed death-ligand 1 (PD-L1) maintenance treatment, radiation therapy, and enfortumab vedotin (EV) therapy. To determine which of the treatments contributed to the therapeutic effect, immunostaining was used. The results indicated that Nectin-4 was expressed in clear cell variant tissues, while programmed cell death protein 1 (PD-1) and PD-L1 expression levels were weak in these tissues. The patient maintained complete remission with these treatments. Two years after the initial treatment, the patient was still alive with no progression or metastasis.

Decreased Volume of Bone Marrow Adipocytes With Sparse Gelatinous Marrow Transformation in a Patient With Pancytopenia With Anorexia Nervosa: A Case Report.

Patients with anorexia nervosa (AN) often have complications of hematologic abnormalities and pancytopenia, which can be fatal. In patients with AN, the rates of anemia, leukopenia, and thrombocytopenia have been reported as 16.7-39%, 7.9-39%, and 5-11%, respectively; in patients with severe AN, the rates of anemia, leukopenia, thrombocytopenia, and pancytopenia have been reported as 47-83%, 49.5-79%, 16.8-25%, and 16.4-23%, respectively. Hematologic abnormalities are often associated with morphological myeloid transformations such as hypoplasia, aplasia, and gelatinous marrow transformation (GMT). Hypocellularity, such as hypoplastic or aplastic, often results in a dry tap, whereas GMT does not usually result in this because of the aspiration of gelatinous material. Therefore, bone marrow aspiration in patients with pancytopenia with AN usually does not show a dry tap. The bone marrow adipocyte (BMA) volume increases in patients with AN, except in those with severe malnutrition. Patients with AN experiencing pancytopenia often exhibit GMT associated with atrophy of the originally increased volume of BMAs. Herein, we report the case of a patient with pancytopenia with AN who exhibited a dry tap on bone marrow aspiration. A bone marrow biopsy revealed sparse GMT with decreased BMA volume and areas of hematopoietic cells, adipocytes, and no GMT. A 13-year-old Japanese girl weighing 25.8 kg (BMI: 10.0 kg/m2) was admitted to our hospital and received nutritional therapy. The patient presented with pancytopenia and fever, prompting the conduct of bone marrow examinations. Bone marrow aspiration resulted in a dry tap, and the bone marrow biopsy revealed sparse GMT with a decreased volume of BMAs. Additionally, an area devoid of hematopoietic cells, adipocytes, or GMT was observed. Nutritional therapy resulted in weight gain and improved pancytopenia. Upon discharge, the patient weighed 40.0 kg (BMI: 15.5 kg/m2) with a normal WBC count, hemoglobin levels, and platelet count. It is significant to study hematological and bone marrow changes because patients with AN often present with hematologic abnormalities. The identification of sparse GMT, which is associated with a decrease in BMA volume and the presence of an area devoid of hematopoietic cells, adipocytes, or GMTs, is a novel finding. The improvement in pancytopenia following nutritional therapy suggests a link between myeloid transformation and malnutrition. Consequently, in patients with pancytopenia associated with AN exhibiting these bone marrow findings, nutritional therapy is necessary.

Effects of Extended Fixation on Advanced Gastric Cancer HER2 Status Assessment Using IHC and FISH.

BACKGROUND/AIM: In gastric cancer, accurate determination of human epidermal growth factor receptor type 2 (HER2) status is crucial for treatment decision-making. However, the optimal formalin fixation time of gastric cancer specimens for HER2 status determination remains unestablished. Here, we investigated real-world data on formalin overfixation and its effect on HER2 status determination in gastric cancer. PATIENTS AND METHODS: We comprehensively analyzed HER2 testing results in 228 gastric cancer specimens, including those subjected to formalin overfixation. Subsequently, we divided 52 resected specimens of advanced gastric cancer into three groups and studied the effects of short-term (6-72 h) and long-term (1 and 2 weeks) fixation on HER2 status determination using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). RESULTS: A total of 21.5% (49/228) of the specimens were HER2-positive, whereas 78.5% (179/228) were negative. Among the HER2-negative specimens, no biopsies were overfixed, whereas 12.5% (9/72) of the surgical resection specimens were overfixed. The HER2 status of the 6-72-h group was 82.7% and 76.9% identical to that of the 1- and 2-week groups, when determined using IHC, and 73.1% and 36.5%, when determined using FISH, respectively. However, HER2 determination was not feasible in 26.9% and 63.5% of the specimens in the 1- and 2-week groups, respectively. CONCLUSION: Formalin overfixation may hinder the determination of HER2 status and should be avoided in gastric cancer sample preparation.

Duodenal follicular lymphoma lacks AID but expresses BACH2 and has memory B-cell characteristics.

We have reported previously that duodenal follicular lymphoma (FL) is distinct from nodal FL and showed more resemblance to mucosa-associated lymphoid tissue lymphoma, and that FL frequently involved the duodenal second portion. In the present study, we examined duodenal FLs and gastric/colonic FLs to clarify the clinicopathological and immunological differences between the tumor types. We analyzed 8 samples of gastric FL, 17 of duodenal ones, and 5 of colonic/rectal ones, and characterized them by immunohistochemistry, immunogenotyping, and histology. Gastric and colonic FLs presented in submucosal to subserosal areas, whereas duodenal ones presented in the mucosal to submucosal layers. Immunohistochemical analysis revealed that duodenal FLs exhibited the following phenotypes: CD10 (+), B-cell lymphoma 2 (BCL-2) (+), BCL-6 (+), activation-induced cytidine deaminase (AID) (-), BACH2 (+), CD27 (+), MUM-1 (-), Blimp-1 (-), and loose CD21 network (duodenal pattern). Gastric/colonic FLs exhibited the following phenotypes: CD10 (+), BCL-2 (+), BCL-6 (+), AID (+), BACH2 (+), CD27 (-), MUM-1 (-), Blimp-1 (-), and a dense CD21 network (nodal pattern). Expression of AID and CD27 in lymphoma cells and the CD21 network pattern were considerably different between duodenal FLs and gastric/colonic ones. Moreover, in situ hybridization revealed that, in the duodenal FLs, BACH2 was expressed at the periphery of the tumor follicle and tumor villi. The number of immunoglobulin heavy-chain variable domains VH4 and VH5 were higher in duodenal follicular lymphomoas than in gastric FLs. The lymphoma cells of duodenal FLs are different from those of gastric/colonic FLs, and duodenal FL is distinct even within the gastrointestinal tract. Somatic hypermutation in immunoglobulin genes and CD27 expression are hallmarks of memory B cells. We suggest that duodenal FL cells are in the memory B-cell stage, and require BACH2 instead of AID for ongoing mutation.