This patient is a 16-year-old girl with a 3-month history of right shoulder pain. The pain is described as occurring intermittently throughout the day. It is not related to any specific activities and tends to be worse at night. There is no history of a traumatic injury to this extremity. Physical examination demonstrates a significant asymmetry when compared with the contralateral shoulder. The right shoulder has a soft-tissue mass adhered to the underlying humerus. It is easily palpable and minimally tender. There are some dilated veins in the skin overlying the right proximal humeral mass. There is no fever or other notable systemic symptoms such as anorexia or weight loss.

Routine blood tests should be performed, including alkaline phosphatase. Perform chest radiograph, anteroposterior (AP) and lateral radiographs of the right proximal humerus and shoulder girdle, bone scan, and computed tomography (CT) or magnetic resonance imaging (MRI) scan of the shoulder girdle. Biopsy should be done to establish tissue diagnosis.

Laboratory examinations including a complete blood cell count (CBC), blood urea nitrogen (BUN), and electrolytes (e.g., alkaline phosphatase, calcium, and phosphorous) are performed, and the alkaline phosphatase is the only result not within normal limit ranges. The reported value of the alkaline phosphatase was markedly high at 600 units. The patient’s white blood count was normal and the sedimentation rate was 18.

A posteroanterior (PA) chest radiograph is normal, but a lytic destructive lesion of the right proximal humerus is easily visualized. AP and lateral radiographs of the right proximal humerus and shoulder girdle show a large, destructive osteolytic and osteoblastic lesion of the proximal third of the humerus. Cortical destruction is observed in these studies. There is a significant soft-tissue component underlying the deltoid muscle, with evidence of extraosseous bone formation arising from the proximal humerus. There is marked periosteal elevation, though the joint space appears to be normal.

CT scans of the right humerus and shoulder girdle show a destructive lesion arising from the right proximal humerus, with a significant soft-tissue component under the deltoid muscle with extraosseous bone formation. The subchondral bone of the humerus is intact without any evidence of destruction or joint involvement by the soft-tissue mass.

MRI examination of the right shoulder girdle demonstrates extensive involvement of the intramedullary space, involving half of the proximal humerus. There is marked cortical destruction corresponding to the finding noted on the CT scan, but a large extraosseous component appears laterally, arising underneath the deltoid. The tumor also extends along the joint capsule. A right shoulder axillary angiogram is performed and demonstrates a hypervascular lesion arising from the right proximal humerus corresponding to the soft-tissue component and bony lesion. There is no obvious evidence of arterial involvement.

A biopsy is performed under CT guidance with a large needle trocar through a single stab wound through the anterior deltoid. Multiple cores are obtained through this puncture site. A frozen pathology section is obtained at the same time, which demonstrates viable spindle-cell tumor with evidence of osteoid formation. There is no evidence of round cells, giant cells, inflammatory cells, or infection.

The differential diagnosis of a destructive lesion of the long bones in an adolescent is very suspicious for a primary malignancy. The most common primary malignant bone tumors are osteosarcomas, Ewing sarcomas, and less often, chondrosarcomas or giant cell tumors. In the adolescent population, the most common malignant bone tumors include osteosarcomas and Ewing sarcomas. A finding of a large soft-tissue mass is characteristic of osteosarcomas. Approximately 95% of osteosarcomas are accompanied by an extraosseous mass. This patient’s history of pain is consistent with that of a primary bone tumor. Tumors arising from the skeletal system are often intermittently to excessively painful during the day, but are characteristically most painful at night. Night pain should be a strong warning for malignant bone pathology. It is rare for tumors arising from the bone to actually involve the neurovascular structures, as seen on the angiogram, but often the major vessels are displaced by the tumor mass itself. The alkaline phosphatase values were markedly elevated. This is a hallmark of, and a tumor marker for, osteosarcoma.

A large core needle biopsy harvested several cores (with CT guidance) through the anterior one third of the deltoid muscle. The soft-tissue component was biopsied, not the bone itself. A frozen section of one core showed high-grade spindle-cell sarcoma. The final pathology showed a highly malignant spindle-cell tumor with the tumor stroma making malignant osteoid.

Osteosarcoma, stage IIB, arising in the right proximal humerus.