Uncommon Presentation of a Rib Osteochondroma Misdiagnosed as a Breast Lesion: A Case Report

Case: Osteochondromas are common benign bone tumors. Rarely, these lesions present on the ribs and can be concerning for a breast mass. This case discusses a healthy 21-year-old female with a firm, fixed, painful breast mass. Her initial ultrasound and 6-month follow-up ultrasound were both benign. The mass gradually increased in size with continued pain over 2 years. Almost two and a half years after presentation, the patient had an additional ultrasound and CT chest revealing a bony exostosis from the anterior aspect of the third rib. Excision was performed in a joint case with orthopedic oncology and plastic surgery, with pathology confirming the diagnosis of an osteochondroma. Conclusion: It is important to consider alternative diagnoses, such as rib osteochondroma, in the differential diagnosis of firm, fixed breast masses in young, postpubescent females.