AXILLARY NODAL METASTASIS WITH UNKNOWN PRIMARY
Rarely, women present with adenocarcinoma meta stases in the
axillary lymph nodes without an identified primary source of cancer.
If the primary cannot be found through clinical breast
examination and standard breast imaging, adenocarcinoma in the
axillary lymph nodes is usually presumed to be caused by a primary
cancer in the ipsilateral breast.
Historically, mastectomy was recommended in this situation.
However, more recent studies have suggested that well-selected
patients who undergo whole breast radiation without mastectomy,
followed by continued mammographic screening of both breasts, can
have equivalent outcome as measured by local recurrence in the
MRI helps resolve the clinical dilemma about mastectomy in these
patients. MRI detects the primary cancer in up to 70% of these
patients, changing the staging from T0 (unknown primary) to the
defined T1 to T3. Once the primary cancer is detected and
histologically proven to be present in the ipsilateral breast,
surgical planning can be made using standard criteria for patient
In several published series, MRI accurately identified the primary
cancer in most patients presenting with axillary adenopathy, an
unknown primary, and a negative clinical examination and
mammogram.[35-41] Overall, MRI will identify the primary in
approximately 59% of women with this diagnosis, allowing them to
pursue more appropriate and focused therapy for the breast
Therefore, for patients with biopsy-proven adenocarcinoma presenting
in the axilla, a normal clinical breast examination, and a negative
mammogram (TxN1-3), breast MRI is indicated to identify a primary
cancer in the breast.