Title: Sonographic Findings of the Primary Mucoepidermoid Carcinoma of the Breast
Running Title: Mucoepidermoid Carcinoma of the Breast
Keywords: mucoepidermoid carcinoma, breast tumor, mammography, ultrasonography, magnetic resonance imaging
Number of Characters in the Title: 74
Number of Words in the Manuscript: 493
Number of Figures: 3
Number of Tables: 0
Mucoepidermoid carcinoma (MEC) is an invasive tumor that has been reported in many organs, such as the salivary glands, lungs, esophagus, and thymus; however, it rarely affects the breast.1Only a few case reports about the primary MEC of the breast are available that provide pathological evidence, which is limited to imaging, including mammography, ultrasonography, and magnetic resonance imaging.
A 38-year-old woman with a history of breast masses for 1 year presented to our hospital with a mass in the right breast, which had been rapidly grown in 1 week. On physical examination, the biggest mass was palpated in the lower outer quadrant of the right breast, which felt pliable but strong, was well-defined and movable. Before being admitted to the hospital, mammography was performed, which revealed a well-defined huge mass with a partly-lobulated boundary (Figure 1).
Initially, breast ultrasound examinations were performed during her hospital admission. Multiple cystic breast masses bilaterally were observed; most of them were oval, anechoic, well-defined, and thin-walled. However, the biggest mass was some solid tissue within the septa-divided cystic spaces with rich blood flow signals and high resistance (Figure 2). No lymph node metastasis was found in the bilateral axillary nodes.
Afterward, magnetic resonance imaging (MRI) of the breast was performed before excising the biggest mass, which showed different signals on T1-weighted and T2-weighted imaging at the solid tissue, while both revealed a high signal at the mass peripherally. Additionally, it was observed that the lateral thoracic artery of the right breast was thicker on maximum intensity projection (Figure 3).
Eventually, the patient underwent surgical resection of the biggest mass and a diagnosis of primary low-grade MEC was confirmed. No recurrence and metastasis were reported during the 6-months follow-up postoperatively.
Most of the case reports have insufficient imaging. Only a few cases of breast MEC mammography have been reported which described an unclear mass with or without accumulation of calcific deposits. Likewise, the studies reporting ultrasound imaging also lacked detailed descriptions and only mentioned minimal details. Most ultrasound images of primary breast MEC show a complex cystic or solid mass with a rough or regular surface.2When breast ultrasound is unavailable or inconclusive, MRI offers more diagnostic information to confirm the characteristics of the mass, including its components and composition; however, the evidence is still too deficient to characterize the findings.
Based on the evidence describing pathological characteristics, primary breast MECs are histologically classified into three categories—low, intermediate, and high grade. These are usually characterized by a prominent cystic component, intraductal papillary proliferation, and solid architecture, respectively. Most low or intermediate-grade primary breast MECs have an indolent behavior whereas high-grade masses could be fatal due to distant metastasis.3
In summary, exploring the imaging manifestations of primary breast MEC in detail is essential for which various imaging modalities, including mammography, ultrasonography, and MRI are available. These modalities are crucial in not only characterizing the mass but may also influence the histological grading of the mass before surgical treatment.