A 29-year-old woman comes to the office due to worsening pain in her right knee. The patient has had increasing knee pain and swelling for the last 3 months, which has prevented her from going to her weekly yoga class and running on the weekends. She has tried taking ibuprofen and putting ice on her knee, but these interventions have provided little relief. The patient has no chronic medical conditions and does not use tobacco, alcohol, or illicit drugs. Temperature is 37.2 C (99 F). On examination, the right knee has mild soft-tissue swelling with no effusion but with decreased range of motion. X-ray shows an expansile lytic lesion at the epiphysis of the distal femur, as shown in the exhibit. Complete blood count and serum chemistries are normal. Which of the following is the most likely diagnosis in this patient?

Question

A 29-year-old woman comes to the office due to worsening pain in her right knee.  The patient has had increasing knee pain and swelling for the last 3 months, which has prevented her from going to her weekly yoga class and running on the weekends.  She has tried taking ibuprofen and putting ice on her knee, but these interventions have provided little relief.  The patient has no chronic medical conditions and does not use tobacco, alcohol, or illicit drugs.  Temperature is 37.2 C (99 F).  On examination, the right knee has mild soft-tissue swelling with no effusion but with decreased range of motion.  X-ray shows an expansile lytic lesion at the epiphysis of the distal femur, as shown in the exhibit.  Complete blood count and serum chemistries are normal.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d964_2b02_bc81_fb6c0c251fb7_MD0003_00 This patient has progressive knee pain with a lytic bone lesion consistent with giant cell tumor of bone (GCTB). GCTB is a benign but locally destructive neoplasm that is most common at the epiphysis of long bones. The incidence is highest in young adults who have reached skeletal maturity, but it can also occur in older adults, typically associated with Paget disease of bone. The course is variable; most patients have only local manifestations (eg, pain, swelling, stiffness, pathologic fracture), but pulmonary metastasis and malignant transformation may occur. X-ray in GCTB characteristically shows an eccentric lytic lesion, often with a multilocular appearance resembling soap bubbles. CT imaging can show greater detail of the mass, and MRI is often indicated to visualize the adjacent soft tissues. The diagnosis is confirmed with biopsy, which shows multinucleated giant cells resembling osteoclasts interspersed with sheets of mononuclear stromal cells. Surgery (eg, intralesional curettage or excision) is first-line treatment. Monoclonal antibodies (eg, denosumab) against the receptor activator of nuclear factor kappa-B ligand (RANKL), which is overexpressed in the stromal cells, can also be used to shrink the tumors. multinucleated giant cells (Choices A and E) Baker (popliteal) cyst is caused by extrusion of fluid from the knee joint into the semimembranosus/gastrocnemius bursa. It is typically seen in patients with underlying knee disorders (eg, osteoarthritis) and presents as an asymptomatic bulge in the popliteal fossa or with pain and swelling in the posterior calf. X-ray findings in osteoarthritis include joint space narrowing, subchondral sclerosis, and osteophyte formation, but the epiphyseal bone is normal. This young patient with no history of joint disease is unlikely to have osteoarthritis or a Baker cyst. joint space narrowing (Choice C) Tibial tubercle apophysitis (Osgood-Schlatter disease) causes pain at the insertion of the patellar tendon. It usually occurs in adolescent and preadolescent patients and frequently follows a rapid growth spurt. X-ray may show avulsion of the tubercle, but the femur is normal. avulsion of the tubercle (Choice D) Patients with advanced hyperparathyroidism can develop increased resorption in cortical bone with subperiosteal thinning and cystic degeneration (osteitis fibrosa cystica). Although x-ray may show lytic lesions, most patients have multifocal involvement, and either symptoms of hypercalcemia (eg, constipation, fatigue; in primary hyperparathyroidism) or a history of chronic renal failure (in secondary hyperparathyroidism). lytic lesions (Choice F) Osteoid osteoma is another benign bone tumor that appears on imaging as a small, round lucency. It typically causes nocturnal pain that is quickly relieved by nonsteroidal anti-inflammatory medications (eg, ibuprofen). small, round lucency Educational objective: Giant cell tumor of bone is a benign but locally destructive neoplasm that is most common at the epiphysis of long bones in young adults. Most patients have local manifestations (eg, pain, swelling), but pulmonary metastasis and malignant transformation may occur. X-ray shows an eccentric lytic lesion, often resembling soap bubbles. The diagnosis is confirmed with biopsy, and surgery is first-line treatment. References: Giant cell tumor of bone. (http://www.ncbi.nlm.nih.gov/pubmed/23378375) Giant cell tumour of bone in the denosumab era. (http://www.ncbi.nlm.nih.gov/pubmed/28365529)

A 29-Year-Old Woman Comes to the Office Due to Worsening