Lymphomas of the Parotid Gland in Denmark: A Nationwide Cohort Study.

Objective: We examined the epidemiology of parotid gland lymphomas (PGL), the incidence, survival rates, clinical features, and association with primary Sjögren's syndrome (pSS).

Methods: This retrospective nationwide cohort study analyzed data from Danish patients diagnosed with PGL between 2000 and 2020. Data were collected from medical records, the National Pathology Register, and the Danish lymphoma database. Statistical analyses included Kaplan-Meier curves, log-rank tests, and Cox proportional hazards models.

Results: A total of 433 patients were included. The incidence rate was 0.39 per 100,000 person-years, with PGL constituting 1.9% of all non-Hodgkins lymphoma in Denmark. The average annual incidence was 2.7% (incidence rate ratio = 1.027, p < 0.01). Follicular lymphoma (FL) was the most common subtype with 154 cases (35.6%), followed by large B-cell lymphoma (LBCL) with 119 cases (27.5%), and extranodal marginal zone lymphoma (EMZL) with 84 cases (19.4%). The median overall survival (OS) for FL was 9.5 years (95% CI 6.9-10.2), with 5-year and 10-year OS rates of 70% and 44%, respectively. For LBCL, the median OS was 7.8 years (95% CI 5.0-8.8), with 5-year and 10-year OS rates of 59% and 33%. EMZL had a median OS of 12.8 years (95% CI 9.0-16.3), with 5-year and 10-year OS rate of 83% and 55%. EMZL was significantly associated with pSS, relative risk 21.97 (95% CI 2.81-171.53). Advanced age, B symptoms, and elevated LDH levels were significantly linked to poorer overall survival.

Conclusion: This study offers new epidemiological, clinical, and prognostic insights, with a focus on their association with pSS.

Level of evidence: 3 Laryngoscope, 2024.