Breast carcinoma presenting with axillary lymph node metastases. An analysis of specific histopathologic features.

Forty-three patients with metastatic carcinoma in axillary lymph nodes from an unknown primary site were studied. Thirty-one women (72%) were subsequently identified as having primary carcinoma in the ipsilateral breast. Based on the histologic patterns of the metastasis, patients were divided into three groups. Type I axillary lymph node metastases were composed of sheets of large, apocrine-like pleomorphic cells with pale to granular pink cytoplasm, large nuclei, and prominent nucleoli. This type was found in two-thirds of the cases. Type II metastases were readily recognizable as characteristic of breast carcinoma and included glandular, cribriform, and papillary patterns and comedonecrosis. Type III metastases demonstrated a mixture of the two previous patterns. Patients proven to have breast carcinoma ranged in age from 33 to 83 (average 58). Among the 31 cases with proven breast carcinoma, mammography was abnormal in 11 (35%). In the 12 other cases (18%), no primary in the breast or other site was demonstrated. Patients not proven to have breast carcinoma had a similar age distribution, comparable proportions of histologic patterns of metastases, and similar survival results to those with a demonstrated breast carcinoma, and none of the 12 patients were later shown to have another primary. The findings described here indicate that when mammary carcinoma presents initially with axillary metastases, it often has a distinctive histological pattern. In most cases this consists of relatively large, apocrine-like cells growing diffusely without forming glands or papillary structures. A minority of metastases have patterns (comedonecrosis; trabecular, glandular, or trabecular growth) more characteristic of the usual spectrum of breast carcinoma. Awareness of this morphological diversity should assist the pathologist in suggesting the breast as a primary site when the initial manifestation is an axillary lymph node metastasis.