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.