Mammary Paget disease (MPD) is considered an intraepidermal manifestation of an underlying mammary carcinoma. In contrast to extramammary Paget disease, invasion of mammary Paget cells into the dermis (invMPD) has not been reported, except for 2 cases described in Rosen’s textbook. Our study was designed to identify the presence of dermal invasion of mammary Paget cells and characterize the associated clinicopathologic features. Slides from 146 MPD patients were retrieved. Six cases of invMPD were identified. One case of invMPD was not associated with an underlying breast cancer, 1 was associated with invasive ductal carcinoma (IDC), 1 with ductal carcinoma in situ (DCIS) with microinvasion, and 3 with DCIS only. The underlying breast carcinomas was separate from the area of invMPD. The depth of invasion, measured from the dermal-epidermal junction to the focus of deepest invasion, ranged from 0.02 to 0.9 mm. The horizontal extent ranged from 0.01 to 4.0 mm. Lymph node with isolated tumor clusters was present in case 1, which had no underlying carcinoma but had the greatest extent of invasion, and in case 3, which had DCIS with microinvasion. One patient (case 1) died of unrelated causes 2 years later, and the remaining patients were alive without disease at last follow-up. In summary, we describe 6 cases of MPD with invasion of Paget cells into the dermis and provide histopathologic criteria for the diagnosis of this rare and underrecognized entity. Further studies are required to determine whether invasion in MPD has clinical significance.
*Department of Pathology, The University of Texas Health Science Center
Departments of †Pathology
§Medical Oncology, The University of Texas MD Anderson Cancer Center
∥Department of Pathology, St Luke’s Episcopal Hospital, Houston, TX
¶Department of Medical Oncology, Dubai Hospital, Dubai, United Arab Emirates
Present address: Xiuzhen Duan, MD, PhD, Department of Pathology, Loyola University Health System, Maywood, IL
Presented in part at the 100th Annual Meeting of the United States & Canadian Academy of Pathology, San Antonio, TX, 2011.
Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.
Correspondence: Nour Sneige, MD, Department of Pathology, Unit 85, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030 (e-mail: firstname.lastname@example.org).