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 Vand erbilt University Hospital, a 63-year-old woman with a 2-cm painless mass i n the right axilla. Mammography was negative, and fine needle aspiration re vealed atypical cells suspicious for malignancy. An excisional biopsy of th e 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 patie nt underwent right modified radical mastectomy. The final pathological repo rt revealed a 0.9-cm primary tumor in the upper inner quadrant of the breas t and 1 of 41 nodes positive for tumor. This case confirms that mammography has low sensitivity in identifying the primary tumor in occult breast carc inoma and illustrates the usefulness of PET in identifying the primary tumo r. We advocate an aggressive approach to evaluation of the breast in women presenting with metastatic adenocarcinoma in the axillary nodes. This evalu ation 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.