Mammary mucocele-like lesions. Benign and malignant.

In 1986 mucocele-like lesions (MLL) were described as benign tumors; subsequent reports identified MLL associated with ductal hyperplasia or carcinoma (CA). To characterize MLL further, we studied 53 lesions from 49 patients, in whom 25 MLL were benign and 28 were malignant (14 in situ, 14 invasive). Two had bilateral benign MLL, and two had bilateral MLL with CA. Patients ranged in age from 24 to 79 years (mean, 48 years). There were no appreciable differences in age, tumor size, or laterality between patients with benign or malignant MLL, although MLL with CA had coarse calcifications more often than benign MLL and were more likely to be detected mammographically. Intraductal carcinoma was micropapillary or cribriform, and invasive carcinoma was usually mucinous. Fewer of the benign lesions were estrogen and progesterone receptor positive. HER2/neu positivity was more common in MLL with CA. Known treatment was as follows: for benign MLL, excisional biopsy was done in 22 patients (one with axillary dissection) and total mastectomy in one patient; for MLL with CA, excisional biopsy was done in 17 patients, biopsy followed by wider excision in four patients (three of whom had axillary dissection), and mastectomy and axillary dissection in five patients (one also had radiotherapy). Follow-up ranged from less than a 1 year to 15 years (mean and median, 3.7 years). Two patients had recurrences in the breast (one benign MLL and one MLL with CA). At the time of this report, all were alive without evidence of disease. We conclude that MLL with CA is a low-grade neoplasm with few clinical differences from benign MLL except for more prominent calcifications, leading to mammographic detection. Excisional biopsy is recommended for benign MLL. Breast-conserving surgery is appropriate therapy for MLL with CA. Radiotherapy is indicated if CA involves margins or if extensive intraductal carcinoma is present.