10. Pathology and Oncology MCQs

Discussion: Curettage and bone grafting typically is the preferred method of treatment for chondroblastoma, with local recurrence rates of approximately 10%. Some clinicians advocate the addition of adjuvants such as phenol. Left alone, these lesions can destroy bone and invade the joint. Large intra-articular lesions may require major joint reconstruction. Wide local excision rarely is required to eradicate the tumor.

DISCUSSION: A ganglion cyst arising from the posterior labrum of the shoulder is a known cause of suprascapular nerve impingement. The MRI characteristics of low-signal intensity on T1 and high-signal intensity on T2 are seen in lesions with a high fluid content. The histology shows a cavity with a thin fibrous lining. REFERENCES: Ferrick MR, Marzo JM: Suprascapular entrapment neuropathy and ganglion cysts about the shoulder. Orthopedics 1999;22:430-434. Post M: Diagnosis and treatment of suprascapular nerve entrapment. Clin Orthop 1999;368:92-100.

slide 1 slide 2 slide 3A patient presents with a hard leg mass and pain with activity. The anteroposterior and lateral radiographs are shown in Slide 1 and Slide 2. An axial computed tomography scan is shown in Slide 3. Which of the following would be the most appropriate treatment:

Based on the location and extent of the tumor, most patients are candidates for limb salvage surgery. The patient has an osteosarcoma; therefore, the treatment of choice is preoperative chemotherapy, wide resection, and reconstruction. There is no difference in survival rates between patients who undergo limb salvage surgery and those who undergo amputation. Curettage and placement of methylmethacrylate is used to treat benign lesions of bone and would not be appropriate in this patient.

DISCUSSION: The radiographs reveal a sessile lesion projecting from the medial aspect of the distal femur. The lesion shares the cortex with the bone and the base communicates with the medullary space of the femur. This is the classic appearance of an osteochondroma, the most common benign tumor of bone.

DISCUSSION: Paget’s disease of bone is a metabolic disorder of bone remodeling. The normally coupled process of bone resorption and deposition is lost, resulting in excessive localized bone resorption and compensatory increased bone formation. Pagetic bone tends to be more brittle; therefore, it is susceptible to pathologic fractures and subsequent deformities. REFERENCES: Lander PH, Hadjipavlou AG: A dynamic classification of Paget’s disease. J Bone Joint Surg Br 1986;68:431-438. Buckwalter JA, Einhorn TA, Simon SR: Orthopaedic Basic Science, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 320-369.

DISCUSSION: The classic MRI appearance of a soft-tissue sarcoma is a well-defined heterogeneous mass deep to the fascia. MRI has greatly enhanced our ability to identify and characterize soft-tissue masses. A common misconception is that sarcomas are infiltrative; therefore, physicians mistakenly exclude the diagnosis of a sarcoma based on a well-defined mass seen on MRI. However, sarcomas grow centrifugally with balloon-like expansion compressing surrounding normal tissue; as such, they appear well defined. Heterogeneity is a characteristic of soft-tissue sarcomas. REFERENCES: Bancroft LW, Peterson JJ, Kransdorf MJ, Nomikos GC, Murphey MD: Soft tissue tumors of the lower extremities. Radiol Clin North Am 2002;40:991-1011.

Surgical margins are classified according to the plane of dissection in relation to the tumor. An intralesional procedure is where the plane of dissection passes through the tumor. A marginal resection involves a resection where the plane of dissection is through the reactive zone of the tumor. A wide resection is through completely normal tissue outside of the reactive zone. A radical resection removes all of the muscles and/or bone of the compartment that are involved by the tumor.

Metastatic bone cancer is common, affecting nearly 5.3% of the nearly 5 million people with cancer in the United States each year. This is a typical presentation of a patient with a newly diagnosed pathologic femur fracture. Without a known history of cancer, this presentation should initiate a complete metastatic work-up including a radiograph of the pathologic site; blood tests; whole-body bone scan; and a CT scan of the chest, abdomen, and pelvis. In current practice, most primary cancers are identified as the result of a metastatic work-up. Approximately 85% to 90% of primaries are determined from the history, physical, blood tests, imaging, and biopsy results.

DISCUSSION: Local control of malignant fibrous histiocytoma of bone typically consists of wide excision. Curettage and bone grafting is a procedure with an intralesional surgical margin, with an unacceptable rate of local recurrence. Prophylactic fixation is considered for patients with metastatic disease. Radiation therapy alone is not adequate for local control of this tumor. Neoadjuvant chemotherapy is often used primarily for systemic tumor control. REFERENCE: Bacci G, Picci P, Mercuri M, Bertoni F, Ferrari S: Neoadjuvant chemotherapy for high grade malignant fibrous histiocytoma of bone. Clin Orthop 1998;346:178-189.

DISCUSSION: The histology shows cells with bubbly, abundant clear cytoplasm typical of physaliphorous cells; therefore, the most likely diagnosis is chordoma. These tumors arise from notochord rests in the upper and lower spine. REFERENCE: Mirra J: Bone Tumors: Clinical, Radiologic, and Pathologic Correlations. Philadelphia, PA, Lea and Febiger, 1989, vol 1, ch 8.

DISCUSSION: The imaging studies show a chondrosarcoma; therefore, surgical treatment is indicated. There is no role for intralesional treatment of an exophytic lesion, particularly in the pelvis. Even obtaining a biopsy specimen risks intrapelvic contamination, although many surgeons would still perform a biopsy prior to a resection to confirm the diagnosis. Chondrosarcoma is considered resistant to both radiation therapy and chemotherapy; therefore, radiation therapy generally is not used except for unresectable lesions. Chemotherapy would be used only for metastatic disease or in patients with high-grade chondrosarcoma. The grade would not be known until after resection, and in this patient, the histology slide showed a grade I neoplasm. Chemotherapy would not be used preoperatively because a cartilage tumor is unlikely to shrink, and in this patient, the lesion is resectable. REFERENCES: Springfield DS, Gebhardt MS, Mcguire MH: Chondrosarcoma: A review. J Bone Joint Surg Am 1996;78:141-149. Marco RA, Gitelis S, Brebach GT, Healey JH: Cartilage tumors: Evaluation and treatment. J Am Acad Orthop Surg 2000;8:292-304.

DISCUSSION: The histology shows findings consistent with metastatic renal cell carcinoma. Renal cell carcinoma metastases are extremely vascular. Preoperative embolization helps minimize the amount of blood loss during curettage of these lesions. REFERENCES: Chatziioannou AN, Johnson ME, Pneumaticos SG, et al: Preoperative embolization of bone metastases from renal cell carcinoma. Eur Radiol 2000;10:593-596. Sun S, Lang EV: Bone metastases from renal cell carcinoma: Preoperative embolization. J Vasc Interv Radiol 1998;9:263-269.

The radiograph and MRI scan show a pedunculated lesion arising from the medial aspect of the distal femoral metaphysis. The cortex of the lesion is contiguous with the cortex of the underlying normal bone. Similarly, the medullary canal of the lesion is contiguous with that of the normal bone. These findings are diagnostic of osteochondroma. Rarely, a secondary chondrosarcoma can arise in a preexisting osteochondroma. This diagnosis is suggested by identifying a cartilage cap that is greater than 1.5 cm thick in a skeletally mature patient. MRI is the best study to rule out a secondary chondrosarcoma. CT also may be used for this purpose but is not indicated in this patient because an MRI has already been obtained. A bone scan is not useful to identify a secondary chondrosarcoma. Similarly, there is no role for biopsy in this patient. No further tests are needed.

The ground-glass appearance on the radiograph, the hot bone scan, and histologic findings of bony spicules without osteoblastic rimming in a background of bland fibrous tissue all suggest fibrous dysplasia. Stress-related pain is common with activity because of the dysplastic bone. Parosteal osteosarcomas are surface lesions. Simple cysts, aneurysmal bone cysts, and eosinophilic granuloma are all possible radiographically; however, the histology is most consistent with fibrous dysplasia.

DISCUSSION: Patients with a pathologic fracture of a unicameral bone cyst or simple bone cyst should first pursue nonsurgical treatment and 4 to 6 weeks of immobilization. Spontaneous healing occurs in fewer than 10% of patients, possibly due to cyst decompression. The most appropriate form of surgical treatment is controversial. Many substances have been injected with variable results. Injection with steroid, bone marrow, demineralized bone matrix, and calcium phosphate/calcium sulfate have been attempted. Curettage and bone grafting and decompression have been attempted. Indications for treatment are based on cyst size, symptoms, and location. Unicameral bone cysts typically resolve as patients reach skeletal maturity.

DISCUSSION: A bone-producing lesion in the metaphysis of an adolescent is most likely an osteosarcoma. The radiographs show a distal femoral bone-producing lesion extending into the surrounding soft tissues. The histologic appearance consists of pleomorphic cells producing osteoid. Ewing’s sarcoma and metastatic neuroblastoma do not produce a matrix. Chondrosarcoma is a radiographically destructive lesion with calcification and cartilage cells on histologic section. An osteochondroma is a benign cartilage lesion that is continuous with the medullary cavity of the underlying bone and extends into a bony lesion and covered by a cartilage cap. REFERENCES: Unni KK: Dahlin’s Bone Tumors: General Aspects and Data on 11,087 Cases, ed 5. Philadelphia, PA, Lippincott-Raven, 1996, pp 143-160. Gibbs CP, Weber K, Scarborough MT: Malignant bone tumors. Instr Course Lect 2002;51:413-428.

The images show an epiphyseal lesion. The MRI scan shows extensive bone edema surrounding the lesion, consistent with chondroblastoma. Histology shows polygonal chondroblasts in a cobblestone-like pattern and areas of calcification consistent with chondroblastoma. Although some giant cells are seen, the age of the patient and the polygonal chondroblasts differentiate this lesion from giant cell tumor. Clear cell chondrosarcoma is an epiphyseal lesion that occurs in an older population, and the cells have clear cytoplasm. This lesion is not producing bone on imaging or histologic specimen, eliminating osteosarcoma. Tuberculous septic arthritis can be an epiphyseal lesion, but granulomas would be seen on histology.

Skeletal muscle contusions are a common cause of morbidity from sports-related injuries. The healing response involves a complex balance among muscle repair, regeneration, and scar-tissue formation. Animal models of muscle contusion have demonstrated a time-dependent histological response to postinjury protocols of immobilization and remobilization. Mobilization initiated after a brief period of immobilization resulted in better penetration of regenerative muscle through limited connective tissue scar in line with native surrounding muscle. Early mobilization in an in vivo muscle contusion model resulted in a progressive increase in myotubule, early nerve regeneration, and reduced inflammation. Immobilization results in disorganized penetration of muscle fiber through dense connective scar tissue with immobilization.

DISCUSSION: The work-up for a patient with an unknown primary lesion that is metastatic to bone includes a search for the primary tumor and other sites of metastasis. This involves conducting a thorough history and physical examination, appropriate laboratory studies, bone scan, chest radiograph, and CT of the chest, abdomen, and pelvis. CT of the brain is not necessary in the early stages of a metastatic work-up.