Recent progress in follicular lymphoma in Japan and characteristics of the duodenal type

Pathogenesis of Gastrointestinal Follicular Lymphomas: Consideration Based on Histopathology and Endoscopic Findings

Gastrointestinal (GI) follicular lymphoma (FL) is the most frequently diagnosed extranodal FL; however, its pathogenesis is debatable. We investigated the distribution, endoscopic, and histopathologic findings of 366 GI FL samples obtained from 298 patients. FLs were most frequently observed in the small intestine (71%), including the duodenum (52%), but were also commonly found in the stomach (15%) and colon (12%). The proportion of granular lesions in the duodenum, terminal ileum, colon, and stomach was 74%, 39%, 24%, and 0%, respectively. Submucosal or ulcerated tumors were frequently observed in the stomach (48%) and colon (52%). Most GI FL showed grade 1 to 2 histology (89%) as well as CD10 + (93%) and BCL2 + (98%) positivity. There were no significant differences in the endoscopic or histologic findings between primary and secondary GI FLs. As known, the mucosa of the small intestine is thin and villous, while the mucosa of the stomach and colon is thicker and has a smooth surface. Granular lesions corresponding to very small FL were detected in the former but rarely in the latter. Nine (7%) patients with primary GI FL developed histologic transformation to diffuse large B-cell lymphoma (n=8) or high-grade B-cell lymphoma (n=1) 10 months to 14 years after the diagnosis of FL. Two patients died of lymphoma. In conclusion, the incidence and endoscopic findings differed, but the histopathology was similar in FLs in each site. These differences might be attributed to variations in each GI site's mucosal structure and the neoplastic follicles' size. Due to its characteristic structure, very small classic FLs might be detectable mainly in the small intestine.

The pathobiology of follicular lymphoma

Follicular lymphoma is one of the most frequent lymphomas. Histologically, it is characterized by a follicular (nodular) growth pattern of centrocytes and centroblasts; mixed with variable immune microenvironment cells. Clinically, it is characterized by diffuse lymphadenopathy, bone marrow involvement, and splenomegaly. It is biologically and clinically heterogeneous. In most patients it is indolent, but others have a more aggressive evolution with relapses; and transformation to diffuse large B-cell lymphoma. Tumorigenesis includes an asymptomatic preclinical phase in which premalignant B-lymphocytes with the t(14;18) chromosomal translocation acquire additional genetic alterations in the germinal centers, and clonal evolution occurs, although not all the cells progress to the tumor stage. This manuscript reviews the pathobiology and clinicopathological characteristics of follicular lymphoma. It includes a description of the physiology of the germinal center, the genetic alterations of BCL2 and BCL6, the mutational profile, the immune checkpoint, precision medicine, and highlights in the lymphoma classification. In addition, a comment and review on artificial intelligence and machine (deep) learning are made.

Upward trend in follicular lymphoma among the Korean population: 10-year experience at a large tertiary institution

Background

Follicular lymphoma (FL) is the second most common non-Hodgkin lymphoma (NHL) in Western countries. However, it is relatively rare in Asia. This study examined epidemiologic characteristics of FL in South Korea, with an emphasis on recent trends of increase in cases.

Methods

We retrospectively examined 239 cases of newly diagnosed FL at a large tertiary institution in Korea (Asan Medical Center, Seoul, Republic of Korea) between 2008 and 2017. Age-adjusted incidence rates and clinicopathological variables were analyzed, and joinpoint regression analysis was used to identify the changes.

Results

The age-adjusted incidence of FL significantly increased during the study period (p = .034), and the ratio of (relative incidence) patients with FL to patients with NHL increased from 4.28% to 9.35% in the same period. Over the 10-year study assessment duration, the proportion of patients with stage III/IV FL (p = .035) and expression of BCL2 (p = .022) or BCL6 (p = .039) significantly increased. From 2013–2017, the proportion of patients with highrisk Follicular Lymphoma International Prognostic Index (FLIPI) score increased (21.5% to 28.7%), whereas that of low-risk FLIPI decreased (55.4% to 38.6%), although those results were not statistically significant (p = .066).

Conclusions

We found an increasing incidence of FL, with a disproportionate increase in the incidence of high-stage disease and recent changes in the clinicopathologic features of the Korean patient population.

Recent Advances in Digestive Tract Tumors: Updates From the 5th Edition of the World Health Organization "Blue Book"

CONTEXT.—

The World Health Organization Classification of Tumours: Digestive System Tumors, 5th edition, was published in 2019 and shows several impactful changes as compared with the 4th edition published in 2010. Changes include a revised nomenclature of serrated lesions and revamping the classification of neuroendocrine neoplasms. Appendiceal goblet cell adenocarcinoma is heavily revised, and intrahepatic cholangiocarcinoma is split into 2 subtypes. New subtypes of colorectal carcinoma and hepatocellular carcinoma are described. Precursor lesions are emphasized with their own entries, and both dysplastic and invasive lesions are generally recommended to be graded using a 2-tier system. Hematolymphoid tumors, mesenchymal tumors, and genetic tumor syndromes each have their own sections in the 5th edition. New hematolymphoid lesions include monomorphic epitheliotropic intestinal T-cell lymphoma; duodenal-type follicular lymphoma; intestinal T-cell lymphoma, not otherwise specified; and indolent T-cell lymphoproliferative disorder of the gastrointestinal tract. This paper will provide an in-depth look at the changes in the 5th edition as compared with the 4th edition.

OBJECTIVE.—

To provide a comprehensive, in-depth update on the World Health Organization classification of digestive tumors, including changes to nomenclature, updated diagnostic criteria, and newly described entities.

DATA SOURCES.—

The 5th edition of the World Health Organization Classification of Tumours: Digestive System Tumours, as well as the 4th edition.

CONCLUSIONS.—

The World Health Organization has made many key changes in its newest update on tumors of the digestive system. Pathologists should be aware of these changes and incorporate them into their practice as able or necessary.

Overview of Gastrointestinal Lymphoproliferative disorders✰

Lymphoproliferative processes which occur in the gastrointestinal tract range from benign reactive processes such as follicular hyperplasia (rectal tonsil) to high grade malignant lymphomas and histiocytic sarcoma. The WHO Classification of Tumors: Digestive System Tumors, 5th Edition was published in 2019 and shows several impactful changes as compared to the 4th Edition published in 2010. WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues 2017 also included detailed changes in hematopoietic neoplasms within the gastrointestinal tract. New entities or renamed hematolymphoid lesions include monomorphic epitheliotropic intestinal T-cell lymphoma, duodenal-type follicular lymphoma, intestinal T-cell lymphoma, NOS and indolent T-cell lymphoproliferative disorder of the gastrointestinal tract. A brief overview of WHO classification of digestive tumors and WHO classification of tumors of hematopoietic and lymphoid tissue is discussed focusing on the changes in the most recent WHO texts. In depth discussions will be presented in other papers in this series.

Synchronous duodenal mucosa-associated lymphoid tissue lymphoma and gastric cancer

Duodenal mucosa-associated lymphoid tissue (MALT) lymphoma is an extremely rare tumor. Herein, we report multidisciplinary treatment of a patient with synchronous development of primary MALT lymphoma of the duodenum and gastric cancer. A 70-year-old woman was referred to our hospital for examination of a gastric cancer initially diagnosed by a local medical doctor. Esophagogastroduodenoscopy showed an elevated lesion with a central ulcer in the lower body of the stomach, and a partially whitish aggregated lesion in the descending portion of the duodenum. Histopathological examination of biopsy specimens from the gastric lesion showed moderately differentiated adenocarcinoma, and duodenal specimens showed low-grade MALT lymphoma composed of atypical lymphoid cells with a lymphoepithelial lesion. The patient underwent distal gastrectomy with regional lymph node dissection for the gastric cancer. Histological examination showed muscularis propria invading adenocarcinoma with two lymph node metastases. After operation, four courses of systemic rituximab treatment were administered for the MALT lymphoma, followed by adjuvant S-1 (tegafur/gimeracil/oteracil) chemotherapy for the gastric cancer. In the 4 months after operation, the patient was well with no evidence of recurrence. To the best of our knowledge, this is the second reported case of synchronous gastric adenocarcinoma and duodenal MALT lymphoma in the English literature.

Development of diffuse large B-cell lymphoma from duodenal type follicular lymphoma: a retrospective study of 23 cases

The incidence and clinical characteristics of histological transformation (HT) from duodenal type follicular lymphoma (DFL) are unclear. A retrospective analysis was conducted to identify the incidence and clinical features of HT from DFL in 23 cases with DFL. The median follow-up duration was 4.6 years (range, 0.8-20 years). HT to diffuse large B-cell lymphoma was observed in 2 of 23 cases during follow-up (8.7%). One of two cases transformed at 21 months later with increased serum lactate dehydrogenase (LDH; 1655 U/L) and abdominal lymphadenopathy. Partial response was achieved after R-THP (pirarubicin)-COP therapy, but the disease progressed. The other case transformed at 8.3 years with an increase of serum LDH (4022 U/L), abdominal lymphadenopathy, and bone marrow involvement. The disease was refractory to DA-EPOCH-R and a high-dose methotrexate/cytarabine regimen. The patient received allogenic peripheral blood stem cell transplantation and finally achieved complete response. Both cases developed HT at nodal or other intestinal lesions with no progression of the primary duodenal lesion. No significant factors for the occurrence of HT were identified. Although the incidence is low, HT could occur in DFL with aggressive clinical manifestations.