Invasive Mammary Paget Disease Without an Underlying Breast Cancer: A Case Report

Abstract Mammary Paget disease (MPD) is a malignant lesion of the nipple-areolar complex and considered an intraepidermal sign of an underlying invasive or in situ carcinoma. In rare instances, mammary Paget cells can invade the dermis. Comprehensive literature review identified 33 such cases. Here, we report a case of a 48-year-old female with invasive MPD, without an associated underlying breast cancer. Only five such presentations are reported. With a presentation of right nipple-areolar excoriation for 2 years, skin punch biopsy was performed and reported as “Paget disease.” Further evaluation with bilateral mammograms failed to show any primary mass or calcifications. Bilateral breast MRI revealed focal nonmass enhancement in upper outer quadrant in both breast, the biopsy of which showed benign breast tissue. Right breast nipple areolar complex resection demonstrated MPD extensively involving the epidermis. Multiple foci of invasive ductal carcinoma are present, growing downward into the nipple dermis, the largest focus being 0.2 cm in greatest dimension. No lymphovascular invasion is identified. The mammary Paget cells are positive for Cam 5.2 and epithelial membrane antigen (EMA) and negative for keratins 7 and 20. The invasive tumor cells are strongly positive for estrogen receptor (100%) and progesterone receptor (75%) and equivocal (2+) for Her2/Neu. FISH analysis showed amplification for HER2 (HER2/CEP17 ratio: 2.75). Four right axillary sentinel lymph nodes are negative for carcinoma. Two of the five patients with invasive MPD described in the literature, and without underlying breast cancer, had a sentinel lymph node biopsy performed. Isolated tumor clusters were present in one of these two cases. In summary, we describe a rare case of invasive MPD without an underlying breast cancer. Although sentinel lymph nodes are important to assess metastasis, further cases are required to evaluate the significance and prognosis of this rare entity.