Epidemiology of Extranodal Diffuse Large B Cell Lymphomas in Algeria: A Study of the Algerian Group of Extranodal Lymphomas (GALEG)

Introduction: Primitive extranodal lymphomas are a heterogeneous group of malignant lymphoid hematological developed from the mucosa-associated lymphoid tissue (MATL) or sites that have acquired MALT after repeated stimulation. The particularity of this type of affection reside: the access to diagnosis which is difficult and therapeutic approach which respond to the ATB, antiviral, surgery and RT. They represent 24-48% of lymph node lymphomas and they are increasing. The incidence of lymphoma is growing in the world, it is approximately 16.8 / 10⁵inhabitants. In Algeria in 2012, the incidence of lymph node lymphomas in adults was 2.24 / 100,000. Lymphomas Diffuse large B-cell phenotype (DLBCL) represent 50-60% of lymphomas, it is the most common histological type.

Goals of the study:

1-analyze the epidemiological characteristics (gender, age, geographical distribution, annual incidence). 2- Identify anatomical sites. 3- Specify the clinical and prognostic features

Patients and methods: It's is a multicenter, retrospective study over a period between 2010-2014. The study population included all pts over 15 years and having an extranodal DLBCL at 18 hematology centers and 4 cancer centers. Data were collected on data sheets distributed to the various services involved in the study. The diagnosis is made on the histological examination of a biopsy of the affected organ. The clinical, biological and imaging results allowed us to classify and identify prognostic factors for pts.

Results: Among 1057 sheets of extranodal lymphomas, the type DLBCL is specified in 562 (53%) cases, distributed in 325 men and 237 women (sex ratio M/F: 1.36). The average age at diagnosis is 51 years (16-88) with a peak in the age group 50-60 years. The overall annual incidence of 0.31/10⁵ inhabitants/year and the specific incidence for patients over 15 years is 0.42 / 10⁵inhabitants/year. PS 0-1: 323 / 543pts (60%). Number of pts (pts) by place of care: Annaba 65, Sétif: 60, CAC Constantine: 53, Tizi Ouzou: 49, Blida Cac: 41, CMPC-hematology: 40, Tlemcen: 30, Beni- Méssous- hematology: 29, CAC CPMC: 24, EHUOran: 23, hematology CAC Batna: 22, CHU Oran: 19, HMRUO: 17, Blida-hematology: 16, HCA:16, SBA: 15, CAC Béni-Messous: 14, EPH Mascara: 10, HMRU Oran: 9, Bejaia: 7, hematology CHU Batna: 2, hematology Cne:1. Number of cases according to anatomical localisation: Stomach: 180, Intestine: 31, Colon 12, Tonsils: 70, Cavum: 31, nasal cavities: 11, Bones: 43, mediastinum: 41, SNC: 29, Skin: 25, Rate / MO :15, Thyroid: 12, soft Parties: 10, Breast: 6, lung / pleural: 5, Liver: 5, Others: 36. The clinical symptomatology is very heterogeneous, specifically of the affected organ. Clinical stage is specified in 549 cases, according to Ann Arbor: SCIE: 272 (49%), SCIIE: 149 (27%), SCIIIE: 31 (6%), SCIV: 97 (18%). The International Prognostic Index adjusted for age (IPIaa) include: for pts less than 60 years: Low (F): 70 (23%), lower intermediate (IF): 130 (43%), intermediate high (IE) : 69 (23%), high (H): 32 (11%); for over 60 years Topics: F: 33 (23%), MI: 53 (37%) IE: 41 (28%), E: 17 (12%).

Comments: As with other types of lymphoma, there is a male predominance and a peak incidence in the age group 50-60 years. The higher number of pts in the center and east of the country is probably related to a denser population in these regions. The histological type DLBCL at 53% is in agreement whith what it is conventionally reported. The incidence of 0.31/10⁵inhabitants/year extranodal DLBCL is lower than the overall nodal DLBCL, however, the incidence of extranodal NHL is rarely determined. The number of cases of extranodal lymphomas described in this study is certainly below the actual number because this group of disorders is supported by various specialties related to the location of lymphoma. Extranodal lymphomas has a clinical polymorphism, but it is recognized that gastric and tonsillar locations are the most common, the other despite their rarity, require attention from management. This type of lymphoma is characterized by a preponderance of localized stages unlike ganglion lymphomas where the extended stages predominate. Likewise distribution by IPIaa not exceeding one pejorative factor is more common.

Conclusion: Extranodal DLBCL are rare, they are characterized by a diversity clinicopathological that challenges us to homogenization of their treatment in multidisciplinary level.