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Spontaneous resolution of a costal osteochondroma presenting as pneumothorax

Although costal osteochondroma is a rare condition, it is important to recognize it because of its potential to cause complications such as pneumothorax, massive hemothorax, and diaphragmatic rupture. Traditionally, patients with a symptomatic costal osteochondroma have undergone surgical resection to remove the lesion and prevent further complications. Here, we present an interesting case of a thorn-like, costal osteochondroma arising from the anterior arc of the left fourth rib in a 12-year-old girl presenting with small pneumothorax. After declining corrective surgery, the patient was symptom free and without recurrence at the 1 year follow up. At the 18-month follow up, the osteochondroma had resolved. A 12-year-old girl presented with intermittent shortness of breath and left chest pain. There was no recent history of trauma. A chest radiograph demonstrated a left-sided apical pneumothorax and a nodular lesion in the mid to lower lung zones (Fig. 1a). The patient was kept under close observation for small pneumothorax. After 12 h, the patient fully recovered without further chest pain or other symptoms. Subsequent chest radiographs demonstrated that the pneumothorax had resolved, but a lung nodule remained unchanged. Chest computed tomography (CT) was performed to evaluate the nodule lesion. On CT scans, the nodular lesion was observed to abut, tightly, a prominent bony spicule on the anterior arc of the left fourth rib (Fig. 1b,c). The bony spicule, measuring 1.6 cm in length with a Y-shaped tip, projected medially and had created a soft tissue lesion immediately adjacent (Fig. 1b,c). From the radiological findings, and suspecting an osteochondroma, we recommend surgical excision of the lesion to prevent potentially serious complications, but the patient refused surgery. She was therefore discharged to return home with instructions to attend follow up (FU) in the outpatient clinic. She was rechecked after 6 and 12 months; no change in her physical or radiographic examinations was seen and she had no recurrence. At the 18-month FU, the osteochondroma at the left fourth rib had resolved, with minimal parenchymal scarring remaining (Fig. 1d,e). Although costal osteochondromas in children are usually asymptomatic, they can lead to complications, such as hemothorax, diaphragmatic rupture, pneumothorax, and lung injury. In our patient, at the time of CT imaging, there was no evidence of bleb or other disease in the left lung, supporting the notion that the likely mechanism of spontaneous pneumothorax was direct shearing by the sharp margins of the costal osteochondroma on the pleura. The lung and diaphragm are dynamic organs whose movement is affected by respiratory mechanisms; a costal osteochondroma is fixed and non-movable, and thus causes injury. This suggests that even a small costal osteochondroma could cause severe complications if it has sharp margins. However, this case did not show recurrence of pneumothorax and resolution was achieved at FU. Based on the clinician’s judgment, clinical FU CT was scheduled every 6 months. However, periodic CT increases radiation exposure, which is a particular concern in children; therefore, use of radiography and CT should be reduced where possible. Several studies reported shrinkage or spontaneous regression of osteochondroma arising from the long bones in children. Patients with symptoms of rib osteochondroma have undergone surgical resection to remove the lesion and prevent further complications, and there has been no report of osteochondroma of the rib spontaneously regressing. However, the appropriate timing of surgical excision and natural history of costal osteochondroma have not been clearly defined, and prophylactic surgical excision of costal osteochondroma is still controversial. Although spontaneous regression of a solitary osteochondroma of the rib is considered a rare phenomenon, the incidence of this lesion is uncertain, as most asymptomatic cases go undiagnosed. According to Aida et al., osteochondroma with a sessile morphology were more prone to shrinkage than the pedunculated form in long bones. Based on their results, Correspondence: Gye Yeon Lim, MD PhD, Department of Radiology, Yeouido St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, 07345, 63 ro 10, Yeongdeungpogu, Seoul. 07345, Korea. Email: shlgy@catholic.ac.kr Received 16 May 2019; revised 12 July 2019; accepted 10 September 2019. doi: 10.1111/ped.14167