Primary Breast Lymphoma in the United States: 1975-2013.

[BACKGROUND] Primary breast lymphoma (PBL) has gained attention with the description of breast implant-associated anaplastic large cell lymphoma (ALCL). Less is known about PBL incidence, treatment, and survival by lymphoma subtype.

[METHODS] The Surveillance, Epidemiology, and End Results (SEER) registry database was queried for patients with PBL as first malignancy, with attention to non-Hodgkin Lymphoma PBL subtypes: diffuse large B-cell lymphoma (DLBCL), follicular lymphoma, marginal zone lymphoma (MZL), and ALCL. Incidence was estimated by age and subtype with joinpoint analyses, along with initial local therapy. Five-year relative and overall survival estimates were compared using z and two-sided log-rank tests.

[RESULTS] PBL incidence (per 1 000 000 women) increased from 0.66 (1975-1977) to 2.96 (2011-2013) with an annual percentage change (APC) of 5.3% (95% confidence interval [CI] = 3.8% to 6.9%, P <  .001) from 1975 to 1999 and no statistically significant change thereafter. Incidence continues to increase for women younger than age 50 years (APC = 2.8%, 95% CI = 1.0% to 4.6%, P = .003) and for ALCL-PBL (APC = 11.8%, 95% CI = 0.2% to 24.9%, P =  .047) and MZL-PBL (APC = 2.3%, 95% CI = -0.2% to 4.9%, P =  .07), with the latter increasing significantly from 1995 to 2013 (APC = 7.5%, 95% CI = 3.4% to 11.8%, P =  .001). Surgery and surgery with radiation declined from 2000 to 2013 as initial local therapy for PBL. Five-year relative survival for PBL improved markedly over four decades and was superior for stage I DLBCL-PBL and stage I follicular PBL than for corresponding systemic presentations.

[CONCLUSIONS] PBL has increased in incidence over the last four decades and continues to increase for younger women and for some subtypes. The rise in imaging and procedures to the breast might enhance diagnostic sensitivity for PBL. Further study of the etiologies of PBL is needed.