|Topic:||18. Lung Cancer, Thoracic Oncology / Adult / Case Report / Thoracic Oncology (TO)|
|Authors:||B. Jalil, N. Maniar, K. El-Kersh; Louisville, KY/US|
An enchondroma is a rare cartilaginous tumor that typically develops in the medullary cavity. Eccentric exophytic expansion is infrequent and is termed ‘enchondroma protuberans’. We present an unusual case of enchondroma protuberans that extended from the rib and presented with chest pain and a lung mass on initial radiographic examination.
A 30-year-old African-American female presented to the pulmonary clinic for evaluation of right-sided chest pain and a 5 centimeter right middle lobe mass found on chest x-ray. Chest computed tomography (CT) revealed a pedunculated mass arising from the inner margin of the 6th rib near the costochondral junction measuring 4.5x3x4.4 centimeters consisting of mixed soft tissue with calcifications (Fig.1). The mass extended into the right middle lobe with associated atelectasis, without pneumothorax or hemothorax. The patient underwent CT guided transthoracic fine needle aspiration biopsy that was non-diagnostic. Subsequently, the patient underwent resection of the mass and adjacent rib via video-assisted thoracoscopic surgery. Lung parenchymal invasion was not seen during the procedure and pathological examination disclosed 5.2x4.5x4.2 centimeters multinodular exophytic mass growing from the pleural surface of the rib with a peduncle measuring 3x1.3 centimeters consistent with benign enchondroma of costal origin. On follow up, the patient reported near-complete resolution of right-sided chest pain and no recurrence of the lesion at 4-year follow-up.
The prevalence of bone tumors originating from the ribs is between 3 and 8%. The most common malignant tumors are metastases and myeloma, while the most common benign tumors are fibrous dysplasia, enchondroma, and osteochondroma. Enchondroma represents about 15% of primary benign rib tumors. It is usually diagnosed in the second or third decade of life and in about 80% of the cases it is located in the anterior costal arch near the costochondral junction. It is usually small in size (typically smaller than 5 cm), well demarcated, lobulated, and occasionally with calcifications. In rare cases, the tumor may cause osseous expansion simulating the radiologic appearance of an osteochondroma, termed enchodroma protuberans. Differentiating these from low-grade chondrosarcomas can be difficult, particularly in cases with osseous expansion. Pain at the site is considered a fracture or malignancy until proven otherwise, and warrants further workup. This case highlights an atypical presentation, both clinical and radiographic, of a benign enchondroma that presented as a lung mass.