Clinicopathologic characteristics of malignant non-hematopoietic tumors first presented as an axillary mass with emphasis on occult breast carcinoma

BACKGROUND: Non-hematopoietic malignancies first presented as an axillary mass constitute a unique clinical presentation. We investigated the incidence of various types of malignancies and aimed to define clinicopathologic variables that may assist in the diagnosis, with focus on occult breast carcinoma (OBC).

DESIGN: We reviewed the pathology reports of cases with non-hematopoietic malignancies of the axillary region in our institution between 2000 and 2016. We included patients who presented first with axillary mass and with the absence of a known primary. We recorded patients' age and gender, tumor characteristics including size, histologic type, number of positive lymph nodes, and the clinical management. Then we focused on BC which were divided into OBC or primary BC (PBC).

RESULTS: There were 100 cases that met our criteria (28 melanoma, 7 sarcoma and 65 carcinoma). For carcinoma cases, there were 42 BC (19 OBC, 17 PBC, and 6 possible OBC), 17 non-BC, and 6 carcinoma of unknown primary (CUP). Tumors found incidentally were more likely to be of breast primary (p = 0.01). Larger tumor size (in mm) favored melanoma or sarcoma over BC, non-BC carcinoma or CUP with median and range 61 (15, 180), 60 (23, 80), 30 (15, 75), 31 (17, 90), 26 (20, 55), respectively (p < 0.001). There were no differences in the histopathologic findings or clinical presentation.

CONCLUSIONS: More than half of the patients with axillary malignancy have a tumor of non-breast origin. Therefore, clinical and pathologic studies are warranted to identify the primary site.