Both primary and secondary breast lymphoma are rare accounting for ~ 0.5% (range 0.3-1.1%) of all breast malignancies.
Breast lymphoma may present either as a palpable mass or as diffuse thickening of the breast. Axillary lymph nodes are often enlarged.
Primary breast lymphoma
Primary lymphoma is less common than secondary lymphoma, and is typically a B cell type of non-Hodgkin's lymphoma (NHL). Primary non-Hodgkin lymphoma of the breast represents only ~ 0.25% (range 0.12-0.53%) of all reported malignant breast tumors.
For a tumor to be labeled as a primary breast lymphoma it is required to fulfill the following criteria 5:
- disease should be in the breast or in close proximity to breast tissue
- no evidence of widespread disease should be there
- no previous history of lymphoma
- ipsilateral lymph nodes may be involved if developing simultaneously with primary breast tumor
Secondary breast lymphoma
There is no single imaging finding diagnostic of lymphoma. Biopsy is typically required for diagnosis. Enlarged intramammary lymph nodes may be seen, but these are nonspecific.
It can have variable mammographic appearances but usually it manifests as a mass or with diffuse marked increase in parenchymal density (often can be bilateral).
The sonographic appearance is most often that of a solid hypoechoic mass, which is again nonspecific.
Both radiologic and clinical appearance are similar to carcinoma and therefore the differential diagnosis is difficult. Microcalcifications are not a usual feature in lymphoma.
Mammographic findings are nonspecific and the following should be considered 9: