**Core Concept**
Duct papilloma of the breast is a benign tumor that arises from the epithelial lining of a breast duct. These lesions are often associated with nipple discharge, which may be bloody or serous in nature.

**Why the Correct Answer is Right**
The most common presentation of duct papilloma is a unilateral, spontaneous, and persistent nipple discharge, often described as bloody or serous. This is due to the tumor's location within the breast duct, causing obstruction and subsequent discharge. The discharge may be more pronounced during or after breastfeeding.

**Why Each Wrong Option is Incorrect**
* **Option A:** While nipple discharge is a common symptom, it is not the only presentation of duct papilloma. Other symptoms like a palpable mass or skin changes are not typically associated with this condition.
* **Option B:** Duct papilloma is a benign lesion, and it is not typically associated with systemic symptoms like fever, weight loss, or pain.
* **Option C:** While some breast tumors may cause nipple retraction, it is not a characteristic presentation of duct papilloma.

**Clinical Pearl / High-Yield Fact**
Duct papilloma is a common cause of spontaneous, unilateral nipple discharge, and it should be considered in the differential diagnosis of any patient presenting with this symptom.

**Correct Answer: C. Nipple discharge.**