Pure mucinous carcinoma of the breast: Is axillary staging necessary?

Background: Mucinous carcinoma of the breast (MCB) may be associated with a low risk of axillary metastases. Methods: To evaluate the incidence of axillary nodal metastasis in MCB, a review of all cases from January 1990 to July 2000 was performed. Pure MCB was defined as all tumor cells being completely surrounded by mucin. Patient demographics, tumor size, estrogen receptor status, total number of dissected lymph nodes, and incidence of nodal metastasis were studied. Deeper sections on the lymph nodes from the pure tumors were performed and stained with low-molecular cytokeratin. Results: Nineteen cases of pure MCB and 41 cases of mixed MCB were identified. Patients with pure MCB were older than those with mixed MCB. Tumor size and estrogen receptor status showed no statistically significant differences between the two groups. None of the patients with pure MCB demonstrated lymph node metastases, whereas 12 of 41 cases with mixed MCB demonstrated metastatic lymph node involvement. Conclusions: Because pure MCB seems unlikely to metastasize, axillary lymph node staging in these patients may not be necessary. The presence of lymph node metastases strongly indicates the presence of a mixed MCB.