Giant Pulmonary Hamartoma with Dominant CD34- Positive Smooth Muscle Cell Component.

Pulmonary hamartoma (PH) is usually a solid mass of less than 4 cm in size that contains cartilage omponents. A 44-year-old Japanese woman received surgical resection of a well-demarcated cystic tumor in the right lung. Resected tissue contained a 13 × 10 × 8 cm-sized solid mass with a prominent unilocular cyst (8 × 6.5 × 5 cm). The tumor was composed of a dominant smooth muscle cell (SMC) component with entrapped glandular respiratory epithelium. There was little cartilaginous or fatty tissue. Immunohistochemically, SMC was positive for smooth muscle actin (SMA) and desmin, as well as CD34. We report a unique case of giant pulmonary hamartoma with a dominant CD34 (+) SMC component.