Occult breast carcinoma presenting as an axillary mass.

Breast carcinoma presents rarely (<5% of cases) as an axillary mass without an obvious primary tumor. The value of mammography in detecting an occult breast carcinoma is low, with a sensitivity of 29 per cent and specificity of 73 per cent. MRI and positron emission tomography (PET) are potentially more sensitive in this setting. We present a case recently seen at the Vanderbilt University Hospital, a 63-year-old woman with a 2-cm painless mass in the right axilla. Mammography was negative, and fine needle aspiration revealed atypical cells suspicious for malignancy. An excisional biopsy of the right axillary lymph node revealed metastatic adenocarcinoma, most likely breast primary. A PET showed increased uptake of 18-fluorodeoxyglucose and 99m Technetium in the right axilla and the right lateral breast. The patient underwent right modified radical mastectomy. The final pathological report revealed a 0.9-cm primary tumor in the upper inner quadrant of the breast and 1 of 41 nodes positive for tumor. This case confirms that mammography has low sensitivity in identifying the primary tumor in occult breast carcinoma and illustrates the usefulness of PET in identifying the primary tumor. We advocate an aggressive approach to evaluation of the breast in women presenting with metastatic adenocarcinoma in the axillary nodes. This evaluation should include clinical examination and mammography in all cases, and PET and MRI in selected cases. PET and MRI may be particularly useful when considering a breast-conserving surgical procedure.