Discussion:
The imaging features of PBNHL are indistinguishable from other
malignancies, but the main aim of imaging in these cases is for
evaluating the disease extent, possible involvement of other sites and
for appropriate treatment planning and follow up for recurrence.
The age of presentation of PBL can vary from 9-85 years and the mean age
is 58 yrs. Both males and females can be affected and it is most common
in upper outer quadrants of the breast. (10,11,12,13) Clinically they
present as single or multiple palpable breast masses or diffuse breast
enlargement. Pain is not a common feature (14). Inflammatory skin change
and overlying skin fixation may be encountered. Nipple or skin
retraction or discharge is
uncommon (6,7,14). In our patient,
painless palpable mass was present on left side and the skin or nipple
changes were not present. Diagnosis is primarily based on
histopathology.
Pathologically, (1, 2) Wiseman and Lia have proposed three criteria for
the definitive diagnosis of primary breast non-Hodgkin lymphoma (PBNHL):
1) primary lesion should be in the breast 2) both mammary tissue and
lymphomatous infiltrate should be seen in close association, and 3)
systemic lymphoma or previous extra mammary lymphoma should be excluded.
Ipsilateral axillary adenopathy may be present which should develop at
the time of primary breast disease.
On mammography the typical appearance is of a solitary, noncalcified
circumscribed mass with adjacent lymphadenopathy. (17). Marginal
irregularity or microlobulations may be seen in some cases (14).
Calcification is not a common feature and multicentric and multifocal
disease may be present. Even miliary appearance or diffusely increased
density have been reported on mammography along with skin thickening.
Ipsilateral axillary adenopathy may be seen (7,12,14,15).
Microcalcifications and spiculations are a rare finding in PBL. (12) In
our case due to diffusely increased glandular density of the breasts,
the lesion was not very well visualized.
Ultrasonographically, breast lymphoma is seen as well-defined or poorly
defined single or multiple masses with hypoechoic or hyperechoic
appearance. They may also present as diffusely hypoechoic breast
parenchyma without a distinct mass (7,14,15). Posterior acoustic
shadowing is not present and the lesions may even have an echogenic rim.
(15). In our case, the lesions in both breasts had hypoechoic appearance
with irregular margins without posterior shadowing. Hyper vascularity
may be present. (7,15) which was seen in one of the left breast lesions
in our patient. The enlarged left axillary node demonstrated loss of
fatty hilum and a rounded shape which is suggestive of pathological
malignant involvement (19).
On MRI, these lesions may be indistinguishable from other invasive
carcinomas. They are seen as heterogeneously enhancing mass with rapid
initial enhancement with washout. (2,18). They show isointense to hypo
intense signal on T1W images and are seen as non spiculated masses. MRI
is highly sensitive for detection of multicentric/ multifocal tumors and
also for the follow up after treatment. Only one case report has
reported the ADC value which was low in their case. In our patient,
bilateral breast lesions showed low ADC values of 0.7-0.9 x
10-3 mm-2/sec.
On FDG PET, these lesions are avid. This is also a useful technique for
staging and treatment response evaluation.
Radiotherapy along with chemotherapy is the mainstay of treatment of PBL
(6,12). Contralateral breast is the most common site of recurrence and
CNS and bone marrow are common sites of metastasis. Miller et al in
their study have proven that concurrent use of radiotherapy after 3
cycle of CHOP has better outcomes than 8 cycles of CHOP alone. Addition
of Rituximab further improves outcomes. PBL tends to relapse to CNS,
therefore, CT or MR image of CNS is necessary during follow-up.
The differential diagnosis in this case includes multicentric
infiltrating ductal carcinoma and metastatic involvement of the breast.
IDC are characterized by spiculated margins, architectural distortion
and posterior shadowing on ultrasound, none of which were seen in our
case. Metastasis to the breast from melanoma, sarcoma, gastric carcinoma
may also present with multiple bilateral breast lesions (20) However FDG
PET failed to show evidence of any other primary in the body in our
case.