Periosteal Chondroma of the Rib: A Rare Case With Documented Interval Enlargement

Periosteal chondroma is a rare benign cartilaginous tumor that typically arises in the metaphyses of long tubular bones, with involvement of the rib rarely reported.Although periosteal chondroma is generally described as a slowly growing tumor, longitudinal documentation of its growth is limited, particularly for lesions arising from the rib.We report a rare case of rib periosteal chondroma with documented interval enlargement.A 54-year-old man had an asymptomatic 8-mm nodule incidentally detected on chest computed tomography (CT) five years earlier.The lesion remained 8 mm during two years of CT surveillance, after which follow-up was discontinued.Three years later, routine chest radiography revealed enlargement of the lesion, and subsequent CT demonstrated a diameter of 20 mm.CT-guided percutaneous needle biopsy favored a benign cartilaginous tumor, with periosteal chondroma considered the most likely diagnosis.However, because of the interval enlargement in an adult patient, a malignant cartilaginous tumor could not be completely excluded, and surgical resection was performed for definitive diagnosis.The tumor was excised en bloc using a combined thoracoscopic and open approach, and histopathological examination confirmed the diagnosis.The patient has remained disease-free for four years postoperatively.Although interval enlargement in an adult patient may raise concern for a malignant cartilaginous tumor, growth alone does not necessarily indicate malignancy.This case highlights the diagnostic challenge associated with interval enlargement of a rib periosteal chondroma.