Primary Mucoepidermoid Carcinoma of the Breast: A Rare Breast Entity

Abstract

Objectives: The imaging features of Mucoepidermoid carcinoma (MEC) of the breast are unfamiliar to the breast radiologists due to its rarity. In this paper, we aimed to review the literature, do an analysis and find a common pattern of those lesions that could potentially give a better understanding of this entity. Methods: A review is performed with searching keywords “mucoepidermoid carcinoma breast”, without limitations in the dates or the article types, in the PubMed database. Information about the number of cases, the age of the patients, the presenting symptom, the time-interval between the onset of the symptoms and the time of diagnosis, the diagnostic approach, the imaging, the treatment and the outcome have been reviewed and tabulated. Results: We identified 40 cases. The mean age of the patients was 57. The commonest symptom was a palpable mass, few months to up to 37 years, prior to the diagnosis, with the size ranging 5-82 mm. On US, the lesions appeared as irregular masses or had cystic benign features. The majority underwent a radical/modified radical mastectomy with a form of axillary lymph node procedure. 15 cases were Highgrade, 3 Intermediate-grade, and 19 Low-grade MEC. No chemotherapy was administered in most cases and in a mean follow-up time of 30 months, 5 died because of metastasis. Conclusion: Due to its rarity, the diagnostic and therapeutic approach of MEC in the breast is not welldocumented, causing challenges in daily practice, even at experienced Breast Centers. Review of the published cases is essential for multidisciplinary team meetings to plan treatment strategies.

Mucoepidermoid carcinoma of the breast: A case report and literature review focused on radiological findings

“…Although MEC is one of the most common malignancies of the salivary glands, [ 1 ] it is an extremely rare entity in other organs, including the breast, thyroid, esophagus, bronchi, pleura, forearm, tonsil, colon, and thymus, with only a few cases being reported. [ 3 , 11 ] Because of its rarity, only 43 cases of breast MEC have been reported in the English literature between 1979 and 2022, [ 3 , 4 ] and the clinicopathological features of breast MEC have not been fully demonstrated.…”

“…In an analysis of published cases of breast MEC, [ 3 ] the mean patient age was 57 years (standard deviation, 15.2 years), with patient ages ranging from 27 to 86 years. Most patients complained of a palpable lump in their breasts, and very few cases presented with a nipple discharge or no clinical symptoms.…”

“…Eight of the 9 cases showed masses with suspicious features on radiological examinations (equivalent to BI-RADS category 4), which required tissue confirmation; however, 1 asymptomatic case of low-grade MEC showed a small oval cyst with no initial evidence of malignancy, which was considered a probably benign lesion (equivalent to BI-RADS category 3). [ 3 ]…”

“…Eight of the 9 cases showed masses with suspicious features on radiological examinations (equivalent to BI-RADS category 4), which required tissue confirmation; however, 1 asymptomatic case of low-grade MEC showed a small oval cyst with no initial evidence of malignancy, which was considered a probably benign lesion (equivalent to BI-RADS category 3). [3] We compared the radiologic and pathological findings in the reported cases and found that all cases of low-grade MEC showed cystic components in the mass, and intermediate-grade MECs showed a solid mass without an internal cystic component on US or MRI. This radiologic finding of low-grade MEC is consistent with the pathological finding showing an internal cystic cavity with abundant mucinous cells, unlike intermediate-or high-grade MEC.…”

“…[ 1 ] MEC of the breast is a rare entity, with an estimated incidence of only 0.2% to 0.3% of all primary breast tumors. [ 2 ] Only 43 cases of breast MEC have been reported in the literature to date, [ 3 , 4 ] and the clinicopathological features of breast MEC have not yet been fully identified. Moreover, most previous studies were reported from a pathological perspective because the diagnosis of breast MEC depends on the pathological examination.…”