**Core Concept**
Paget's cells are a hallmark of Paget's disease, a condition characterized by the presence of abnormal cells in the breast tissue. These cells are a result of the malignant transformation of normal breast epithelial cells. The underlying mechanism involves the disruption of the normal epithelial-to-mesenchymal transition (EMT) process, leading to the formation of these characteristic cells.

**Why the Correct Answer is Right**
The correct answer is related to the characteristic feature of Paget's cells, which is their presence in the skin overlying the breast, particularly in the areola. These cells are large, pale-staining epithelial cells with a characteristic appearance under the microscope. They are often seen in the epidermis and dermal papillae, and are associated with underlying ductal carcinoma in situ (DCIS) or invasive breast cancer. The presence of Paget's cells is a strong indicator of breast cancer, and their identification is crucial for making an accurate diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not accurately describe the characteristic feature of Paget's cells.
**Option B:** This option is incorrect as it is a feature of other types of cancer, not specifically related to Paget's cells.
**Option C:** This option is incorrect as it describes a different type of cell altogether, not related to Paget's disease.

**Clinical Pearl / High-Yield Fact**
Paget's cells are often accompanied by signs of inflammation, such as eczema or dermatitis, which can lead to a delay in diagnosis. A high index of suspicion is required to diagnose Paget's disease, and biopsy of the affected skin is often necessary to confirm the diagnosis.

**Correct Answer: D. Intraductal spread of cancer cells to the skin overlying the breast.**