**Core Concept**
Migratory thrombophlebitis is a condition characterized by the occurrence of recurring episodes of thrombophlebitis, where blood clots form in the veins and then migrate to other locations. This condition is often associated with underlying malignancies and systemic inflammation.

**Why the Correct Answer is Right**
The condition is most commonly linked to malignancy, particularly pancreatic cancer. The migratory nature of the thrombophlebitis is thought to be due to the release of pro-coagulant substances by the tumor cells into the bloodstream. These substances promote the formation of blood clots, which then migrate to other sites in the body, leading to recurring episodes of thrombophlebitis. The exact mechanism is not fully understood, but it is believed to involve the activation of the coagulation cascade and the release of tissue factor.

**Why Each Wrong Option is Incorrect**
* **Option A:** Migratory thrombophlebitis is not typically associated with atrial fibrillation, which is a risk factor for stroke and other thromboembolic events, but not specifically migratory thrombophlebitis.
* **Option B:** While cancer can cause thrombophlebitis, the migratory nature of the condition is not typically seen in non-small cell lung cancer.
* **Option D:** Systemic lupus erythematosus (SLE) can cause thrombophlebitis, but it is not specifically associated with migratory thrombophlebitis.

**Clinical Pearl / High-Yield Fact**
Migratory thrombophlebitis is a "Trousseau's sign" of occult malignancy, a classic clinical correlation that should prompt further investigation for underlying cancer.

**Correct Answer:** C. Pancreatic cancer