A 10-year-old boy first complained of right knee pain two months prior to presentation. There was no traumatic event to explain the pain and no prior viral or bacterial illness. Radiographs taken earlier at another facility were initially pronounced normal. One month later, repeat x-rays showed a possible hairline fracture, and MRI was ordered. MRI documented a destructive lesion in the right distal femur with a soft-tissue mass that was worrisome for primary bone malignancy.
The boy was placed on weight-bearing restrictions and was given a wheelchair. Unfortunately, he fell from the wheelchair and sustained a pathologic fracture through the lesion (see Figure 1). He was transported to the hospital and admitted. A biopsy was performed with a closed reduction, as the fracture was maligned. The patient was placed in a long leg cast with a pelvic band.
His history was previously unremarkable. He was taking no medications and had experienced no recent illnesses. His surgical/medical history was positive for a tonsillectomy at an early age and a fracture of the right proximal femur at age 2. On examination, he was noted to be talkative with his family but guarded during conversations with staff.
His physical exam was positive for pain at the right distal femur and knee with palpation; otherwise, all other systems were unremarkable. The patient was in too much pain to range the knee and had been placed in a long posterior leg splint (prior to surgery and application of the cast). Distally, his right lower extremity motor and sensory function were intact.
The patient’s vital signs were within normal limits, and results from his blood chemistries and alkaline phosphatase and C-reactive protein levels were unremarkable. Findings on the complete blood cell count were slightly abnormal: Hemoglobin was 11 g and the hematocrit, 33% (both within normal limits); however, in the differential there was an elevation in segmented neutrophils (72%, compared with a reference range of 31% to 61%), with Döhle bodies present—possibly signifying acute and/or chronic systemic infection or malignancy. The lymphocyte count represented 11% of the total white blood cell count (range, 28% to 48%), and platelets were 82 x 103/mL (normal range, 150 to 350 x 103/mL). The patient’s erythrocyte sedimentation rate was 44 mm/h (normal range, 0 to 20).
Result from pathology were positive for osteosarcoma, telangiectatic type. The patient underwent a nuclear medicine bone scan that showed no metastases, and chest CT was negative for pulmonary lesions as well. After a psychology consult, the boy was gently told about his condition.
Treatment then proceeded, including surgical placement of a double-lumen chest catheter for delivery of neoadjuvant and adjuvant chemotherapy. Doxorubicin, cisplatin, and methotrexate were used because the boy was enrolled in an international cooperative trial through the Children’s Oncology Group for treatment of localized osteosarcoma.
Discussion
Osteosarcoma (OS) is the most common primary bone malignancy.1,2 Approximately 5% of all pediatric patients with tumors present with this diagnosis, and about 400 new cases are diagnosed in the United States each year.1 Most osteosarcomas develop in the bones of the lower extremities and in the humerus, affecting males more often than females.1-3 This kind of malignancy is frequently seen during the adolescent growth spurt, but it can affect patients of any age.1,2 Patients usually present with pain or functional limitation in gait or daily activities or both.1-3
The telangiectatic subtype of OS is a rare, aggressive variant that represents 2% to 12% of all cases of OS.4-6 Telangiectatic OS (TOS) is characterized by multiple aneurysmally dilated, blood-filled cavities with high-grade sarcomatous cells seen in the peripheral rim and septae.3,7,8 This process can cause the lesion to resemble an aneurysmal bone cyst, explaining why some cases of TOS are misdiagnosed—with delayed time to treatment and increased morbidity and mortality.3,5 Generally, TOS patients are more likely than other OS patients to have tumors of femoral location, larger lesions, and normal alkaline phosphatase values. Many have pathologic fractures on presentation.7
The medical literature chronicles a long debate regarding the difference in mortality between patients with OS and those with TOS. It was once believed that patients with TOS were at higher risk for recurrence (especially those with a pathologic fracture) and mortality. However, in recent studies examining newer neoadjuvant and adjuvant chemotherapies, mortality rates for the two conditions are similar and certainly lower than they were many years ago.7,8 In one study, a better histologic response was reported to neoadjuvant chemotherapy in patients with TOS than with OS.7
Diagnosis
The first diagnostic tool used for patients with suspected OS or TOS is a plain radiographic film. A TOS lesion is lytic, with no areas of sclerosis, and almost always involves the long bones. It is poorly defined, destroying the cortex with formation of periosteal bone and invading the soft tissue. An initial pattern of parallel striations is highly suggestive of TOS.5