Diminished Number or Complete Loss of Myoepithelial Cells Associated With Metaplastic and Neoplastic Apocrine Lesions of the Breast

Abstract

The presence of myoepithelial (ME) cells is considered an important feature in the vast majority of benign breast lesions. Recently, a case showing the absence of myoepithelium in a mammary duct with apocrine metaplasia was reported. To investigate the status of ME cells associated with apocrine metaplasia, the distribution of ME cells in 59 metaplastic and intraductal proliferative apocrine lesions was evaluated using immunohistochemical expression of p63 and Calponin. p63 showed a diminished number of ME cells and increased intermyoepithelial nuclear distance in ducts with all variants of apocrine metaplasia and proliferation compared with normal glands. In the majority of cases, Calponin showed a continuous ME layer. In 6 cases, including an apocrine papilloma, there were definitive ME gaps confirmed by both markers, in the absence of atypia and with preservation of the basement membrane. In all cases, there was frequent heterogeneity in the distribution of ME cells in ducts harboring apocrine cells and even in various papillae within papillary lesions. In summary, benign and noninvasive apocrine lesions can show reduction and occasional complete loss of ME cells. This observation is particularly important when evaluating apocrine papillary proliferations, in which the absence of ME cells may lead to overdiagnosis of atypia and/or malignancy. The observation suggests that at least 2 ME markers should be used when evaluating apocrine lesions, and that a malignant diagnosis should be based on features of the proliferating cells until more data become available on the significance, if any, of the absence of ME cells in apocrine lesions.

A case of intracystic apocrine papillary tumor: Diagnostic pitfalls for malignancy

“…Although a lack of myoepithelial markers is commonly used as a hallmark for papillary carcinoma, it has reported that apocrine lesions, either benign or malignant, can show reduction and occasional complete loss of myoepithelial cells [1,8]. Tramm et al [8] described that a malignant diagnosis with apocrine changes of the breast cannot yet solely rely on the presence or absence of myoepithelial cells, and should be based on the overall morphology, i.e., the cytologic and architectural features.…”

“…Tramm et al [8] described that a malignant diagnosis with apocrine changes of the breast cannot yet solely rely on the presence or absence of myoepithelial cells, and should be based on the overall morphology, i.e., the cytologic and architectural features.…”

“…Furthermore, histologic evaluation of malignancy is potentially difficult, particularly in low-grade tumors, because even non-neoplastic apocrine lesions may lack myoepithelial cells [2,8].…”

Atypical Apocrine Adenosis: Diagnostic Challenges and Pitfalls

“…The cytologic features of apocrine cells can be worrisome and, if associated with a reduction or loss in the myoepithelial cell layer, may prompt an erroneous diagnosis of malignancy. 3 Data regarding the relationship between apocrine metaplasia and invasive breast cancer are controversial; some authors have found an increase risk when associated with proliferative lesions, whereas others have found no such association. 5,6 It has been hypothesized that the same stimuli that cause breast cancer could also cause apocrine metaplasia.…”

“…1 The loss of myoepithelial cells around benign and neoplastic apocrine lesions is well documented (Figure 2). 3 Apocrine cells can be found in several different histologic lesions and are often regarded as apocrine change. Among benign lesions with apocrine cells are apocrine metaplasia, apocrine adenosis, papillomas, fibroadenomas, and apocrine adenoma.…”