SESSION TITLE: Medical Student/Resident Cardiothoracic Surgery Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Osteochondroma’s are benign tumors most commonly found on the long bones of the leg, pelvis or shoulder blade. Usually benign, much of the management is set around observation and symptom control. The next step would be surgical excision of the tumor along with pathological analysis and close monitoring for malignant transformation or recurrence. This case further supports possible complications of osteochondromas. CASE PRESENTATION: A 21 yo M with no significant past medical history presented with right sided posterior back pain along the 6th-9th rib. Pain was sharp, worsened with inspiration and movement and radiated to the right shoulder. An XR Chest showed moderate right pleural effusion along with a mass projecting over the right anterior 6th and 7th intercostal space. A CT Chest showed and exophytic sclerotic/well corticated bony lesion arising from the inferomedial aspect of the anterior right sixth rib measuring 3.1 x 3.8 x 3.3 cm. It was invading he intercostal space between the sixth and seventh rib along with the diaphragm at the anterolateral sulcus. Additionally, a right-sided pleural effusion was better visualized showing material in the inferior aspect consistent with blood products. An US-Guided thoracentesis drained 1L of cloudy/bloody fluid. No malignant cells identified and no growth on culture. CT Surgery was consulted and patient underwent excision of the chest wall tumor including partial resection of the 6th rib. The 7th rib did not show any involvement. The chest cavity was also entered where a large loculated hemothorax was seen. This was evacuated along with decorticating of the right lower lobe due to thickened pleura and old blood products. The exophytic mass and rib were sent to pathology for gross and histologic examination. The histologic features showed a cartilaginous cap, trabecular bone, normal hematopoiesis characteristic for osteochondroma. DISCUSSION: Upon literature review it seems there are several case reports reported in the literature showing complications caused by osteochondromas of the thoracic cage. Much of the literature review showed hemothorax as the most common complication as well as diaphragmatic and intrapericardial penetration. This case report seeks to further report another case of a osteochondroma arising from the rib presenting as a hemothorax along with diaphragmatic involvement. Additionally, similar case reports reviewed in literature shows his presentation may be a common complication of osteochondromas arising from the rib. CONCLUSIONS: Osteochondromas, although mostly benign may present with complications should they arise from sites other than the long bones of the body where they are most commonly found. One of the most common complications seen in literature is hemothorax if arising from the thoracic cavity. Clinicians should be aware of this presentation of a pleural effusion and mass arising from the rib. Reference #1: Kitsoulis P, Galani V, Stefanaki K, et al. Osteochondromas: review of the clinical, radiological and pathological features. In Vivo. 2008 Sep-Oct;22(5):633-46PDF) Reference #2: Keith G. Buchan, Vipin Zamvar, Kayapanda M. Mandana, E. Nihal, P. Kulatilake, Juxtacardiac costal osteochondroma presenting as recurrent haemothorax, European Journal of Cardio-Thoracic Surgery, Volume 20, Issue 1, July 2001, Pages 208–210, https://doi.org/10.1016/S1010-7940(01)00721-7 Reference #3: Harrison, N. K., Wilkinson, J., O'Donohue, J., Hansell, D., Sheppard, M. N., Goldstraw, P. G., Davison, A. G., & Newman Taylor, A. J. (1994). Osteochondroma of the rib: an unusual cause of haemothorax. Thorax, 49(6), 618–619. https://doi.org/10.1136/thx.49.6.618 DISCLOSURES: No relevant relationships by Rajeev Sharma, source=Web Response