**Core Concept**
Eczema of the nipple-areola complex, also known as eczema of the nipple or perinuclear eczema, is a condition characterized by scaly skin around the nipple and areola, often accompanied by intermittent bleeding. This condition is typically unilateral and is associated with an underlying pathological process.

**Why the Correct Answer is Right**
The scaly skin around the nipple and areola is due to the presence of an inflammatory response, which leads to the formation of an eczematous lesion. The intermittent bleeding is a result of the breakdown of the epithelial layer and the underlying dermis. This condition is often associated with a Paget's disease, which is a type of intraepithelial adenocarcinoma.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because eczema of the nipple-areola complex is not typically associated with systemic symptoms such as fever or weight loss.
**Option B:** This option is incorrect because mastitis is an infection of the breast tissue, which may present with symptoms such as pain, redness, and swelling, but is not typically associated with scaly skin around the nipple.

**Clinical Pearl / High-Yield Fact**
Eczema of the nipple-areola complex is a diagnostic challenge, and a biopsy of the affected area is often necessary to rule out underlying malignancies.

**Correct Answer:** C. Paget's disease of the nipple.