Non-Hodgkin's lymphoma may originate in, or spread to, any extranodal organ. Breast lymphoma is a rare disease, either as a primary site or as secondary involvement, representing 0.04–0.5% of malignant breast tumours [7
]. It is almost always of non-Hodgkin's type. Secondary involvement of the breast in patients with diffuse disease is more common [8
Most patients with primary lymphoma of the breast develop distant disease to other regions. Within the breast, the most common primary lymphomas are B cell (more rarely T cell) non-Hodgkin's lymphoma. They appear at an elderly age with focal or diffuse localization and usually they are unilateral. Early diagnosis is crucial for clinical outcome [9
Lymphomas are a distinct possibility in the diagnosis of breast tumours. PNHL of the breast remains a diagnosis of exclusion, and the diagnosis cannot be made without a very thorough evaluation [4
]. If a patient presents with a rapidly growing breast tumour, lymphoma should be considered before any surgical intervention is performed. Early decision is vital considering the aggressive nature of the lesion and the prognosis. A high index of suspicion and an understanding of the clinical behaviour of PBL are necessary for proper patient management [7
The most common symptoms of breast lymphoma are a painless breast mass, most frequently located in the outer quadrants [10
]. Skin retraction, erythema, peau d'orange appearance, and nipple discharge are uncommon in lymphomas [11
]. In 50% of cases ipsilateral axillary node involvement is present.
A distinct mammographic or sonographic pattern has not been reported in the literature because primary lymphoma shows no specific characteristics which differentiate it from other benign and malignant breast disorders [8
]. Mammography usually demonstrates a well-circumscribed, uncalcified mass with sharp or minimally irregular margins [12
On Magnetic resonance imaging (MRI) primary lymphoma is more commonly visualized as a lobulated lesion with expansive and infiltrating features. MRI findings are non-specific: in the literature, patterns of primary lymphoma with variable signal intensity and morphology have been reported [2
]. Despite its non specific signs, MRI plays a major role in the determination of the extent and number of lesions, and in the evaluation of cutaneous, subcutaneous and nodal involvement of the contralateral breast.
The definitive diagnosis is therefore histological and allows the planning of surgery (lesion removal) or medical therapy (chemotherapy +/- radiotherapy). Both clinical stage and histological subtype of the lymphoma appear to be important in determining the prognosis of breast lymphomas.