Contributed by Oana Radu, MD and Miguel Reyes-M˙gica, MD
A 5 month-old male infant was brought to the Emergency Department by his parents with persistent, worsening shortness of breath, tachypnea and wheezing. The boy was lethargic, anorexic. He had a history of poor sleep, fussiness and crying for two days. No fever, diarrhea, vomiting, drooling, foreign-body ingestion or stridor were noted. No asthma, recent illness or antibiotic ingestion, home treatment, recent infectious exposure or immunizations were recorded. There was evidence of dehydration, with limited tearing and decreased urine output. Oral intake was limited.
A chest CT without contrast showed large, thin-walled cysts occupying most of the left hemithorax. A small portion of aerated and collapsed lung was present in the left upper thorax. The largest cyst was approximately 8 cm. There was significant mass effect with mediastinal shift to the right. The right lung was essentially clear. There was no evidence of pneumothorax or pleural effusion, and no hilar or mediastinal adenopathy was noted. The impression was of congenital cystic adenomatoid malformation of the lung.
GROSS PATHOLOGIC FINDINGS
The specimen consists of a portion of lung with several collapsed cysts (7.0 x 6.0 x 2.0 cm) (Fig.1). The largest cyst showed tan-gray, delicate, glistening, and paper-thin (less than 0.1 cm in thickness) wall. When perfused with formalin, it reaches approximately 7.0 cm in diameter. No solid or papillary nodules or masses project from the inner surface of the cyst wall. A smaller cyst, with a collapsed cavity, is present (3.0 x 1.0 x 1.0 cm). A spongy area is seen in the lung parenchyma (4.0 x 3.0 cm); its cut surface is up to 0.4 cm thick and displays numerous small cysts, which do not exceed 0.5 cm in diameter.
Fig. 1. Multiloculated, cystic lung lesion. Cyst walls are smooth.
A multicystic lung lesion is present. There is no cyst content. The cyst walls show a simple, bland-appearing epithelium with a subjacent proliferation of elongated, spindly, wavy cells in a loose, myxoid stroma. A cambium-layer is seen in many areas. The cells have a high nuclear-cytoplasmic ratio, irregular nuclear borders with occasional folded nuclei and inconspicuous nucleoli. The cytoplasm is sparse, dark grey and wispy. Areas of primitive cartilage formation are present focally.
Fig. 2. Hematoxylin-eosin sections show a multicystic mass composed of simple cysts, lined by a bland, simple, cuboidal epithelium; The septa contain a proliferation of spindle cells with little , dark grey cytoplasm, occasionally forming primitive cartilage.
Immunohistochemical studies show scattered positive desmin staining of the septal stroma. The cells are negative for MyoD1 and myogenin. There is nuclear S100 staining in the areas of primitive cartilage (Fig. 3).
Fig. 3. Immunohistochemical staining with desmin (left) and S100 (right).