Parosteal (juxtacortical) chondrosarcoma of the humerus associated with regional lymph node metastasis. A case report.

Recurring parosteal (juxtacortical) chondrosarcoma of the humerus occurred in a 79-year-old man. Roentgenograms of the left humerus showed minimal cortical irregularity and a large soft tissue mass without calcification or periosteal reaction. Magnetic resonance imaging (MRI) showed a multilobular tumor of high intensity (T2-weighted imaging) without marrow involvement. During the left shoulder disarticulation an enlarged axillary lymph nodes was discovered and removed. Macroscopic examination of the disarticulated humerus showed a large yellow parosteal mass, which looked like cartilage, completely surrounding the humeral shaft. The marrow cavity was almost normal except for a small erosion at the site of the olecranon fossa. The histologic diagnosis of the mass was Grade 2 chondrosarcoma of parosteal (juxtacortical or periosteal) origin associated with regional lymph node metastasis. The features that made this case unique were a long history of the tumor (for 32 years), minimal cortical destruction of the bone by the tumor, and regional lymph node metastasis. This case illustrates the differential diagnosis of the parosteal chondrosarcoma from periosteal osteosarcoma and extraskeletal myxoid chondrosarcoma.