**Core Concept:** Gestational trophoblastic disease is a group of conditions characterized by the presence of abnormal trophoblastic tissue in a woman's body after a normal or abnormal pregnancy. Metastases in these conditions primarily involve the lungs, liver, and brain due to the high vascularity and permeability of these organs.

**Why the Correct Answer is Right:** In gestational trophoblastic disease, the abnormal trophoblastic cells have the ability to invade and spread to various organs, a process called "metastasis." The most common sites for these lesions include the lungs, liver, and brain.

**Why Each Wrong Option is Incorrect:**

A. **Lungs:** Although the lungs are a common site of involvement, the correct answer is not just limited to this organ. The other two options, liver and brain, are also involved.

B. **Liver:** Similar to lungs, the liver is another common site for trophoblastic disease involvement, but the correct answer includes all three organs: lungs, liver, and brain.

C. **Brain:** The brain is also commonly affected, making this option incorrect as it does not encompass all three organs involved (lungs, liver, and brain).

D. **Lymph nodes:** While lymph node involvement is possible in some cases, the correct answer does not specifically mention this site.

**Clinical Pearl:** The presence of trophoblastic disease should prompt a thorough examination for involvement of multiple organs, as the disease can affect different tissues and organs, including lungs, liver, and brain.

**Correct Answer:** .