Significance of Myoepithelial Cell Layer in Breast Ductal Carcinoma in situ With Papillary Architecture With and Without Associated Invasive Carcinoma

Abstract

IntroductionThe significance of absence of myoepithelial cells in circumscribed papillary breast lesions is controversial. When the DCIS with papillary architecture is associated with adjacent conventional invasive carcinoma, the size and stage of the carcinoma could vary substantially depending on whether the intraductal papillary component lacking a periductal ME cell layer is interpreted as invasive or intraepithelial/in situ. DesignIn a retrospective search of the pathology database at our institution for papillary DCIS (PDCIS), solid papillary carcinoma (SPC), and encapsulated papillary carcinoma (EPC) from 2001 to 2014, 73 lesions (42 PDCIS, 19 SPC, 12 EPC) with and without associated invasive carcinoma were identified and reviewed. Forty-five lesions (22 PDCIS, 14 SPC, and 9 EPC) were associated with invasive carcinoma. ResultsMajority of PDCISs (37 of 42) demonstrated retained myoepithelial cells around periphery of the ducts. Three cases showed discontinuous staining and 2 cases showed absent myoepithelial cells in the periphery of the ducts. No lymph node metastases were seen in DCIS in the absence of histologic evidence of invasion regardless of absence of ME cells around foci of DCIS. With a median follow-up period of 107 months, six distant metastases occurred, all in patients with invasive carcinoma. ConclusionsThe absence of ME cells around ducts harboring the PDCIS, SPC, or EPC is not indicative of an invasive process. The prudent use of morphologic criteria is critical to avoid overstaging and overtreatment.