International retrospective observational cohort study aimed to describe a molecular classification for NMZL.

Already existing and coded tumor biological material and health-related patient data will be retrospectively collected from institutional biobanks and patients' charts or electronic medical records upon receipt of ethical approval. Each patient enrolled in the study will be assigned to a unique identification numerical code upon registration in the study. The unique identification code will be used to record health-related data and to label biological samples. The coded biological material will be transferred to the coordinating center at the Oncology Institute of Southern Switzerland and Institute of Oncology Research in Bellinzona. Health-related data will be collected in the eCRF (OpenClinica). Data quality will be insured by query generation.

Annotated baseline features will include date of diagnosis, date of lymph node biopsy, age, gender, ECOG PS, Ann Arbor stage, LDH, number and location of extranodal sites, bone marrow involvement and percentage, peripheral blood involvement, number of nodal sites, B symptoms, lymph nodes larger than 7 cm, Hb, platelets, lymphocytes, beta-2-microglobulin, albumin, HCV infection, serum paraprotein and type.

Annotated follow-up features included date of progression to a disease requiring treatment, type of first line treatment, date of start of first line treatment, date of progression after first line treatment, date of second line treatment, type of second line treatment, date of transformation, date of death, cause of death, date of last follow-up.

Mutation analysis, immunoglobulin gene rearrangement analysis, copy number aberration analysis, structural variant analysis and DNA methylation profile will be performed by next generation sequencing of genomic DNA extracted from the lymph node biopsy. Gene expression will be assessed by next generation sequencing of RNA extracted from the lymph node biopsy.

Inclusion Criteria:

1. Male or female adults 18 years or older
2. Diagnosis of NMZL on lymph node histology after Jan 1st, 2000
3. Availability of tumor material from lymph node (either frozen or FFPE) collected when the patient was treatment naïve
4. Availability of the baseline and follow-up annotations

Exclusion Criteria:

1. Nodal spread of a clinically occult extranodal MZL (this must have been ruled out by carefully evaluating the extranodal tissues draining to the involved lymph nodes by imaging or endoscopy)

Patients with diagnosis of NMZL on lymph node histology