Intrathoracic lipomas: Their clinicopathological behaviors are not as straightforward as expected

Background. Lipomas are a common type of benign tumor, and may involve numerous sites. They are common in the subcutaneous region of the upper back, neck, and shoulder, but are rarely seen in the thoracic cavity. Intrathoracic lipomas are a type of deep-seated lipoma, unlike subcutaneous lipomas. Due to the rarity of intrathoracic lipomas, little is known about their clinicopathological features. Methods. We conducted a retrospective review of the clinicopathological records of 10 patients who had undergone surgical resection for intrathoracic lipomas during a 16-year period (1991 to 2006). Results. There were 9 men and 1 woman with a mean age of 57.9 years. The number of lesions was one in 9 patients and two in 1 patient. Symptoms caused by the tumor were seen in only one patient. Radiographically, the tumors showed well-defined, homogeneous, and fatty density masses/nodules. Intrathoracic lipomas were most frequently seen in the parietal pleura. The resected tumor size ranged from 1.0 to 6.0 cm. Pathologically, three lesions showed an infiltrating type in which mature fat cells were seen between and within muscle or nerve fascicles. One of these three ended in an incomplete resection because the tumor infiltrated the brachial plexus. One patient had a recurrent tumor arising from a resected margin. Conclusions. Intrathoracic lipomas should be surgically resected if they are detected, because the possibility of liposarcoma or infiltrating development of the tumor cannot be excluded preoperatively. We think that surgical resection of the tumor, rather than conservative management by close observation alone, is a safer treatment.