Salivary gland tumors of the lung is rare, and the most common types are mucoepidermoid carcinoma and adenoid cystic carcinoma. In past reports, ACC of the breast occurred in patients between the ages of 25 and 86 years, with a disproportionate number occurring in comparatively elderly women. The most common area of onset is subareolar and in the vicinity of the areola (approx. 50%), and the tumor often appears as a spherical, mobile mass under palpation. The ACC of the breast does not favor the left or right side and tends not to occur bilaterally, and breast pain at the tumor site is a characteristic clinical symptom in approximately 14% of patients. This type of breast pain is speculated to involve perineural infiltration of tumor cells and contraction of myoepithelial cells. ACC of the breast has no characteristic imaging findings and often appears as a sharply marginated shadow on mammography and ultrasonography. In our patient, a palpable mass without pain was found in the vicinity of the areola. ACC is a biphasic tumor composed of ductal and myoepithelial cells. Myoepithelial cells have dark angled nuclei and scant cytoplasm, resulting in a basaloid appearance. ACC demonstrates three main histological growth patterns, the most common being the cribriform pattern, followed by the tubular pattern. The least frequent and most aggressive pattern is the solid pattern, which is more often associated with lymph node and distant metastasis. The tubular pattern consists of simple tubules lined by inner ductal and outer myoepithelial cells, and the cribriform pattern is composed predominantly of myoepithelial cells with myxoid or hyalinized globules. The solid patterns have solid nests composed of sheets of basaloid cells. Lymphovascular invasion and lymph node metastasis are uncommon, while perineural invasion is extremely frequent. High-grade transformation is observed in a small number of patients and is associated with a high risk of lymph node metastasis, distant metastasis and disease-related death. Focal squamous metaplasia and differentiation can be observed in patients with high-grade transformation. Immunohistochemically, ductal or luminal cells are positive for CK7, CAM5.2, and CD117, and myoepithelial cells express smooth muscle actin (SMA), S100, calponin, P63, P40, and GFAP. MYB overexpression is a sensitive but nonspecific immunomarker for adenoid cystic carcinoma and is a nuclear marker that is preferentially expressed in myoepithelial cells.
Surgery is now recognized as the primary treatment for breast ACC patients. However, due to the rarity of this pathological type, there is no clear guarantee in the selection of a detailed surgical method for this disease, resulting in differences in treatment. Ro et al. suggested that the operation method should be selected according to the ACC grade. Tumor lumpectomy should be used for Grade I tumors, mastectomy should be used for Grade II tumors, and mastectomy plus lymph node dissection should be used for Grade III tumors. Here, we will discuss the operation methods for classic breast ACC and SBACC.
A clinical study of 478 patients with classic breast ACC reported that relapse occurred after local excision. The treatments included tumor lumpectomy plus adjuvant RT, tumor lumpectomy alone, mastectomy alone and mastectomy plus adjuvant RT. K–M analysis revealed that patients receiving tumor lumpectomy plus adjuvant RT had better survival than patients receiving other treatments, indicating that lumpectomy plus adjuvant RT can improve survival and that BCS is a reasonable choice for breast ACC patients.
In conclusion, our results show that the majority of ACCs were triple-negative, but our study also included a small number of hormone receptor-positive breast cancers. Compared with other types of breast cancer, ACC has no specificity for imaging, and FNAC may be a useful tool for diagnosis. The final diagnosis can only be assessed based on the results of histopathological and immunohistochemical examinations.