Q. A 60-year-old postmenopausal female presents to your clinic with complaints of a right breast lump associated with skin changes and nipple discharge. She reports noticing a lump in her right breast for the past two months, which has gradually increased in size. She also has noticed thickening of the skin over the lump and a nipple discharge that is brownish in color. She denies any history of breast cancer in her family. On clinical examination, a firm, irregularly shaped lump measuring approximately 3 cm is palpable in the upper outer quadrant of the right breast. The overlying skin is thickened and retracted, and there is a discharge from the right nipple. No palpable axillary lymph nodes are noted. Mammography reveals an ill-defined mass with coarse calcifications in the right breast. Ultrasound-guided core biopsy is performed, which shows characteristic features of Paget's mammary disease of the breast. Which of the following histological descriptions is most consistent with this diagnosis?