Invasive Paget's Disease of the Breast: A Staging Pitfall Mimicking pT4 Disease.

Invasive Paget's disease of the breast is a rare entity with therapeutic challenges. Herein, we report three patients with Paget's disease of the breast with dermal invasion, of which two cases had coexistent invasive breast carcinoma, while the third had an extensive in situ component. Case 1 was a 49-year-old lady presenting with nipple ulceration and discharge along with concomitant multicentric right breast lesions detected on mammography. Breast conservation surgery was performed which revealed extensive high-grade ductal carcinoma in situ on histopathology, associated with invasive Paget's disease. The patient completed adjuvant radiotherapy and shows no evidence of disease at present, four months following the completion of therapy. Case 2 was a middle-aged woman of 45 years, who was detected with multiple hypoechoic space-occupying lesions in the right breast on ultrasonography. Modified radical mastectomy was performed which showed a tumor-infiltrating lymphocyte-rich breast carcinoma along with invasive Paget's disease. Following surgery, she is currently on adjuvant chemotherapy with no evidence of disease. Case 3 was a 47-year-old lady presenting with a lump in the right breast with nipple ulceration. Microscopic examination of the modified radical mastectomy specimen showed a high-grade invasive breast carcinoma along with invasive mammary Paget's disease. Follow-up imaging showed generalized lymphadenopathy. The patient was advised adjuvant chemotherapy; however, she was lost to follow-up after receiving the first cycle of treatment. We present three cases of invasive Paget's disease of the breast highlighting the importance of recognition of this rare entity with distinct therapeutic implications.