**Question:** Following thoracotomy, in a 20-year-old man a lesion is detected in the right lower lung lobe and is found to be nonfunctioning lung tissue that is served by vessels separate from those of the adjacent lung tissue. What is the most likely diagnosis?

A. Bronchogenic cyst
B. Congenital cystic adenomatoid malformation (CCAM)
C. Congenital lobar emphysema (CLE)
D. Congenital pulmonary airway malformation (CPAM)

**Correct Answer:** C. Congenital lobar emphysema (CLE)

**Core Concept:** Congenital lobar emphysema (CLE) is a rare congenital pulmonary abnormality characterized by the enlargement of the air-filled spaces in a lobe of the lung. In this case, the lung tissue is nonfunctional, and the blood supply is separate from the adjacent lung tissue.

**Why the Correct Answer is Right:** The correct answer, Congenital lobar emphysema (CLE), is chosen because of the following reasons:

1. Nonfunctional lung tissue: CLE presents with nonfunctional lung tissue, which is consistent with the given scenario.
2. Separate blood supply: CLE demonstrates vessels separate from those of the adjacent lung tissue, aligning with the provided information.

**Why Other Options are Incorrect:**

A. Bronchogenic cyst: Bronchogenic cysts are cystic lesions containing respiratory tract epithelium, usually found in the mediastinum or pleura, not in the lung parenchyma.
B. Congenital cystic adenomatoid malformation (CCAM): CCAM refers to cystic lung lesions caused by developmental abnormalities, but the provided information focuses on nonfunctional lung tissue and separate blood supply, which doesn't align with CCAM.
D. Congenital pulmonary airway malformation (CPAM): CPAM is a group of congenital lung lesions characterized by abnormal lung development, but the given scenario emphasizes nonfunctional lung tissue and separate blood supply, which does not match the characteristics of CPAM.

**Clinical Pearl:**

Congenital lobar emphysema (CLE) is a rare congenital lung malformation characterized by the enlargement of the air-filled spaces within a lobe of the lung. It is often associated with a patent ductus arteriosus, which allows blood to bypass the lungs and shunt blood directly to the heart, leading to hypoxia and cyanosis. Patients with CLE may require surgical intervention to relieve pressure on the adjacent functioning lung tissue and improve oxygenation.