10. Pathology and Oncology MCQs

The imaging studies and histology are consistent with high-grade osteosarcoma. The standard treatment for osteosarcoma is neoadjuvant chemotherapy combined with wide surgical resection that can be performed with amputation or limb salvage depending on characteristics unique to each tumor and each patient. In most patients, limb salvage surgery can be performed with reconstruction using allografts and/or megaprostheses. Osteosarcoma is poorly responsive to radiation therapy. Chemotherapy alone, in the absence of appropriate surgery, has not proven effective.

The patient has a large deep anterior thigh mass that has imaging characteristics of mature fat. Intramuscular lipomas are effectively treated with marginal resections with very low recurrence rates. Large lipomas often have small amounts of intralesional signal changes frequently representing trapped muscle fibers and do not necessitate more extensive margins.

DISCUSSIONFigure 2 depicts a typical unicameral bone cyst with a pathologic fracture. The decision to treat this lesion should be based on the amount of cortical thinning. If these lesions involve a pathologic fracture, many surgeons will treat them nonsurgically to see if the fracture stimulates healing of the cyst. If the cyst wall remains thin or the patient is symptomatic, then treatment is directed at decreasing cyst volume, increasing cortical thickness, and eliminating symptoms. This can be accomplished by curettage and grafting, injection with autogenous bone marrow, or grafting with 1 of the many available bone void fillers. In some cases, internal fixation may be required. This typically is accomplished with flexible intramedullary nails.Figure 3 shows a typical nonossifying fibroma. These benign lesions are usually incidental findings on a radiograph and often resolve in adulthood. Treatment usually is not required, and these lesions typically do not produce symptoms.Figure 4 shows an osteoid osteoma of the femoral neck. This is characterized by a central radiolucent nidus surrounded by reactive bone with increased radiodensity. These lesions are painful because of the large amount of prostaglandin they secrete. They temporarily respond to oral anti-inflammatory drugs. Treatment is directed at eliminating the nidus and can be done through curettage, but radiofrequency ablation, which allows for a minimally invasive approach, is often used today.Figure 5 shows diskitis with vertebral osteomyelitis. The disease is characterized by fever and back pain. Movement is extremely uncomfortable for these children, and they may adopt unusual postures to alleviate pain. The MRI shows involvement of 1 vertebrae and an adjacent disk. Left untreated, this condition often spreads to involve multiple vertebrae and also can cause an epidural abscess. Treatment during the early stages is IV antibiotics. Many orthopaedic surgeons also use bracing to prevent late vertebral collapse.Figures 6a through 6c show septic arthritis of the ankle with metaphyseal osteomyelitis. The recommended treatment is incision and drainage followed by IV antibiotics. MRI may be considered before surgery to assess for an associated osteomyelitis or abscess that may also necessitate surgical debridement. Increasingly, these scenarios are managed with a rapid transition to oral antibiotics.

The patient has lung cancer metastatic to the left humerus that is mildly to moderately symptomatic. Radiographically, the lesion is small and is not associated with significant cortical destruction. Metastatic lesions in the upper extremity have a lower incidence of pathologic fracture than lesions in the lower extremity.

The images show a large, almost circumferential, mass surrounding the diaphysis of the femur. The intramedullary signal is normal with minimal cortical destruction, both findings that should be abnormal in conventional osteosarcoma and Ewing’s sarcoma. There are very low-signal striations representing osteoid formation that would have a sunburst radiographic pattern. This indicates an osteogenic lesion. Myositis ossificans is not indicated because studies would reveal zonal ossification starting in the periphery rather than the more central pattern seen in this patient. This appearance is typical for periosteal osteosarcoma.

Marjolin's ulcer refers to malignant transformation that occurs within chronic wounds, burn scars, or chronic osteomyelitis sinus tracts. The most common histologic type by far is squamous cell carcinoma, which tends to be highly aggressive and has a high rate of metastasis in this setting.

Elastofibroma dorsi is a benign, slow-growing, soft-tissue tumor most commonly found in the subscapular region (deep to the latissimus dorsi and rhomboids) of older individuals. It is bilateral in up to 50% of cases. The MRI appearance is characteristic, showing alternating streaks of fibrous tissue (similar signal to muscle) and adipose tissue. It is a classic cause of snapping scapula syndrome.

The radiographs reveal a predominantly lytic, destructive lesion of the distal femur, although there is a hint of some blastic change as well. The lesion has violated the cortex, and there is mineralization outside the cortex laterally. The lateral radiograph suggests a soft-tissue density. These aggressive changes on radiographs in this age group are strongly suggestive of osteosarcoma.

The patient has osseous Coccidioidomycosis ('Valley Fever'), which is endemic to the southwestern US. The hallmark histological finding is spherules containing endospores. Treatment for fungal osteoarticular infections typically involves surgical debridement followed by systemic antifungal therapy, commonly Intravenous Amphotericin B for severe disease, or prolonged oral azole therapy (Itraconazole or Fluconazole).

Bisphosphonates have been reported to reduce the incidence of new osseous lesions and prevent an increase in size of existing lesions. Zoledronic acid has been reported in clinical trials to decrease the skeletal complications of patients with multiple myeloma and with bone metastases from solid tumors. Results also have demonstrated that zoledronic acid delays the initial onset of bone complications by more than 2 months in patients with non-small-cell lung cancer and other solid tumors.

DISCUSSION: Lymphangiosarcomas that arise in pre-existing lymphedema are aggressive malignancies (i.e., Stewart-Treves syndrome) that require resection or amputation.

Celiac sprue results in rapid gastrointestinal transit and fatty stools that impair the absorption of calcium and vitamin D and result in nutritional-deficiency osteomalacia with secondary hyperparathyroidism. Serum findings include low or normal calcium, low phosphate, elevated alkaline phosphatase, low 1,25(OH)2D, and increased PTH levels. Secondary hyperparathyroidism is associated with a variety of conditions including malabsorption syndromes.

A Morton's neuroma is not a true neoplastic neuroma. Histologically, it is characterized by perineural fibrosis, epineural degeneration, and demyelination of the interdigital nerve secondary to chronic repetitive microtrauma.

The histologic findings of perineural fibrosis, local vascular changes, and endoneurial edema are characteristic of Morton's neuroma. It is an entrapment neuropathy causing a reactive degeneration, rather than a true neoplasm.

DISCUSSION: There are a number of important technical details in performing a biopsy. Incisions should always be longitudinal in the extremity. Good hemostasis is important in avoiding contamination from hematoma. The approach should avoid neurovascular structures and go through a single muscle belly when possible. Although a frozen section should be obtained to ensure adequate viable tissue has been obtained, definitive diagnosis is not necessary at the time of the frozen section.

The incidence of malignant transformation or the formation of a secondary malignancy in pagetic bone is estimated to be less than 1%. Osteosarcoma is the most common secondary malignancy, followed by fibrosarcoma and chondrosarcoma. Ewing’s sarcoma arising in pagetic bone has not been reported.

The radiographs reveal a destructive lesion in the metaphysis of the distal femur with periosteal changes and an associated soft-tissue mass with subtle mineralization. This suggests an aggressive malignant process. In this age group, the most likely diagnosis is osteosarcoma.

Synovial sarcoma is characterized by the t(X;18)(p11;q11) translocation, resulting in the SYT-SSX fusion gene. It commonly presents near joints in young adults and often exhibits a biphasic histology.

Tumor necrosis greater than 90% following neoadjuvant chemotherapy is the single most important prognostic indicator for overall survival in osteosarcoma patients. It reflects the tumor's sensitivity to the systemic treatment.

Metastatic renal cell carcinoma and thyroid carcinoma lesions are highly vascular. Preoperative angioembolization within 24 to 48 hours of surgery is critical to significantly reduce intraoperative blood loss.