A 6-month-old female infant from Delhi presents with a 3-week history of progressive respiratory distress, feeding difficulty, and recurrent respiratory tract infections. Chest radiograph shows a large, well-defined, radiolucent mass occupying the left hemithorax with mediastinal shift to the right and compression of the left lower lobe bronchus. The mass is filled with air-fluid levels and contains multiple cystic spaces of varying sizes. Ultrasound of the abdomen is normal. What is the most likely diagnosis?

Explanation

## Diagnosis: Congenital Cystic Adenomatoid Malformation (CCAM) ### Clinical Presentation The 6-month-old with progressive respiratory distress and recurrent infections fits CCAM, which typically presents in infancy with respiratory symptoms. The normal abdominal ultrasound excludes diaphragmatic hernia (which would show bowel loops in the thorax). ### Imaging Findings **Key Point:** CCAM is characterized by **multiple cystic spaces of varying sizes** within the affected lung, with air-fluid levels and mediastinal shift. The lesion is **intra-pulmonary** and **air-filled** (unlike sequestration, which is typically solid). **High-Yield:** Classic radiological features: - Large, radiolucent mass with multiple cysts - Air-fluid levels (especially when infected) - Mediastinal shift and compression of adjacent structures - Most commonly affects the **lower lobes** (60% left, 40% right) - Normal diaphragm (unlike diaphragmatic hernia) ### CCAM Classification (Stocker) | Type | Cyst Size | Prognosis | Presentation | |---|---|---|---| | Type 1 | Large (>2 cm) | Best | Respiratory distress in infancy | | Type 2 | Medium (0.5–2 cm) | Intermediate | Mixed presentation | | Type 3 | Small (<0.5 cm) | Worst | Hydrops, fetal demise | | Type 4 | Large, peripheral | Variable | Rare | **Clinical Pearl:** CCAM is a developmental abnormality of the respiratory bronchioles with abnormal proliferation of terminal bronchioles. It does NOT have a systemic blood supply (unlike sequestration). Prenatal diagnosis is now common via fetal ultrasound or MRI. ### Differential Imaging Features | Feature | CCAM | Sequestration | Diaphragmatic Hernia | |---|---|---|---| | Cystic appearance | Multiple cysts, air-filled | Solid, homogeneous | Bowel loops | | Systemic blood supply | No | Yes (aorta) | No | | Diaphragm | Normal | Normal | Defective | | Location | Intra-pulmonary | Intra- or extra-pulmonary | Thorax (herniated bowel) | **Mnemonic:** CCAM = **C**ystic **C**ongenital **A**denomatoid **M**alformation = **C**ysts **C**ontaining **A**ir **M**ultiple. ### Management 1. **Prenatal:** Serial ultrasound, fetal MRI if indicated; consider fetal intervention if hydrops develops 2. **Postnatal:** - Supportive care (oxygen, antibiotics for infections) - **Definitive:** Lobectomy or segmentectomy (surgical resection is curative) - Timing: Elective resection after 3–6 months to allow stabilization **Warning:** Do NOT confuse CCAM with bronchopulmonary sequestration—sequestration is a **solid, non-aerated** mass with **systemic arterial supply** (usually from the descending thoracic aorta), whereas CCAM is **cystic and air-filled** with **no systemic supply**.