Primary Invasive Paget's Disease in a Clinical Practice: A Case Report

Invasive Paget's disease (IPDN) is a rare phenomenon characterised by invasive carcinoma localised to the nipple. It is associated with Paget's disease of the nipple (PDN) whereby Paget cells locally invade the underlying epidermis. Often in PDN, histopathological confirmation is needed, due to a lack of clear symptoms on clinical presentation. An 82-year-old female with single duct ectasia presented to the breast clinic in September 2023 with a tender, inflamed right nipple with a necrotic appearance. The lesion was excised, and an ultrasound scan showed right U2, implying no underlying malignancy. Microscopy showed Paget's disease with underlying ductal carcinoma in situ and two small (0.4 and 0.3mm) foci of dermal invasion by Paget cells in keeping with IPDN. Research suggests that dermal invasion by Paget cells has little effect on clinical outcome and prognosis depends largely on the associated underlying malignancy. However, all cases of IPDN with deep invasion or penetration of Paget cells into the dermis have the potential for regional and distant lymphatic spread. In extramammary Paget's disease, depth of invasion has been associated with poorer survival. Therefore, wide variability in clinical patterns and presentations of PDN mandates that a careful clinical approach correlated with in-depth histopathological evaluation is adopted in all cases.