**Core Concept**
Mondor's disease is a rare condition characterized by thrombophlebitis or inflammation of the superficial veins, typically affecting the breast or chest wall. This condition is often associated with trauma, surgery, or infection.

**Why the Correct Answer is Right**
Mondor's disease is caused by the thrombosis of the superficial veins, which can be triggered by various factors such as trauma, surgery, or infection. The inflammation is usually localized to the affected area and can cause pain, redness, and swelling. The condition is often self-limiting and resolves on its own with supportive care.

**Why Each Wrong Option is Incorrect**
**Option A:** Mondor's disease is a type of breast cancer. **Incorrect because** Mondor's disease is a benign condition and not a type of cancer.
**Option B:** Mondor's disease is a condition of the deep veins. **Incorrect because** Mondor's disease affects the superficial veins.
**Option C:** Mondor's disease is caused by a viral infection. **Incorrect because** Mondor's disease is typically caused by trauma, surgery, or infection, but not a viral infection specifically.

**Clinical Pearl / High-Yield Fact**
Mondor's disease is often associated with breast surgery or trauma, and prompt diagnosis and treatment can help prevent complications.

**Correct Answer: D. Mondor's disease is a rare condition characterized by thrombophlebitis or inflammation of the superficial veins, typically affecting the breast or chest wall.**