10. Pathology and Oncology MCQs

The clinical and radiographic findings are pathognomonic for an enchondroma, the most common primary bone tumor of the hand. The standard management for an enchondroma presenting with a pathologic fracture is to allow the fracture to heal first, followed by elective curettage and bone grafting.

DISCUSSION: It is generally accepted that reconstructions of the proximal tibia are associated with the highest incidence of failure, probably because of poor soft-tissue coverage, the need for extensor mechanism reconstruction, and other anatomic issues. It also may be related to the fact that patients with tumors of the proximal tibia, in general, have a better prognosis and better survival rates than patients with tumors located elsewhere in the body. Reconstructions of the proximal humerus may be more durable because they are not involved in weight-bearing activities. REFERENCE: Horowitz SM, Glasser DB, Lane JM, Healey JH: Prosthetic and extremity survivorship after limb salvage for sarcoma: How long do the reconstructions last? Clin Orthop 1993;293:280-286.

DISCUSSION: The patient has an aneurysmal bone cyst. The fluid-fluid levels seen on the MRI scan are typical for aneurysmal bone cyst, and the histology is consistent with a cystic lining. Vascular lakes, multinucleated giant cells, reactive bone, fibrovascular tissue, and an absence of atypical cells or numerous mitoses are seen histologically. Aneurysmal bone cysts will typically continue to grow and cause further bone destruction; therefore, observation is not recommended. Steroid injections are not effective. A thorough curettage of the cyst lining and bone grafting are required. Wide resection and chemotherapy are reserved for more aggressive tumors. There is no evidence of infection radiographically or histologically. Telangiectatic osteosarcoma should also be considered in the differential diagnosis; therefore, biopsy is an important part of the work-up. REFERENCES: Wold LA, et al: Atlas of Orthopaedic Pathology. Philadelphia, PA, WB Saunders, 1990, pp 232-233. Simon M, et al: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, pp 194-196.

Parosteal osteosarcoma occurs on the surface of the metaphyseal regions of the distal femur or the proximal humerus most commonly. The treatment is wide surgical resection versus limb salvage. Dedifferentiated chondrosarcoma has a moth eaten appearance and may occur as a transformation of chondrosarcoma. Treatment is resection and prognosis is poor. Low-grade intramedullary chondrosarcoma is also treated with surgical resection. High-grade intramedullary osteosarcoma is usually treated with pre-op chemo and resection. The only tumor listed where radiation is an option is Ewings tumor.

DISCUSSION: Dedifferentiated parosteal osteosarcoma designates high-grade transformation of conventional low-grade parosteal osteosarcoma. Unlike conventional parosteal osteosarcoma, where wide surgical excision alone is considered adequate treatment, patients with dedifferentiated osteosarcoma are treated with neoadjuvant chemotherapy and wide local resection. Recognition of dedifferentiated areas with angiography can localize the area that should be biopsied and thus render an accurate diagnosis. Percutaneous biopsy of hypervascular areas should prompt the administration of chemotherapy and wide local excision to optimize patient outcome. REFERENCES: Sheth DS, Yasko AW, Raymond AK, et al: Conventional and dedifferentiated parosteal osteosarcoma: Diagnosis, treatment, and outcome. Cancer 1996;78:2136-2145. Lewis VO, Gebhardt MC, Springfield DS: Parosteal osteosarcoma of the posterior aspect of the distal part of the femur: Oncological and functional results following a new resection technique. J Bone Joint Surg Am 2000;82:1083-1088.

DISCUSSION: The figure shows the missing pedicle or “winking owl” sign that is characteristic of tumor involvement of the cortical bone of the pedicle. None of the other pathologic processes commonly gives this radiographic picture. Thinned, but not missing pedicles, have been described as a normal variant. REFERENCES: McLain R, Weinstein J: Tumors of the spine, in Herkowitz HH (ed): The Spine, ed 4. Philadelphia, PA, WB Saunders, 1992, p 1173. Charlton OP, Martinez S, Gehweiler JA Jr: Pedicle thinning at the thoracolumbar junction: A normal variant. Am J Roentgenol 1980;134:825-826.

DISCUSSION: The histologic features of multiple myeloma are distinctive for this lesion. The plasma cells are round or oval and have an eccentric nucleus and prominent nucleolus. These characteristics and a clear area next to the eccentric nucleus representing the prominent Golgi center are pathognomonic for plasma cells. Lymphoma is in the differential diagnosis; the most frequent types that occur in bone are large cell or mixed small and large cell types. The histologic appearance of the specimen is not consistent with the other choices. REFERENCE: Dorfman HD, Bodgan C: Immunohematopoietic tumors, in Dorfman HD, Bogdan C (eds): Bone Tumors. St Louis, MO, Mosby, 1998, Chapter 12.

DISCUSSION: Osteoid osteoma is a round or oval, well-circumscribed lesion with a radiolucent nidus. A small area of calcification may be present within the center of the nidus. The radiolucent nidus is surrounded by a thick rim of sclerotic bone. These diagnostic features are frequently better seen on CT. An increase in cyclooxygenase activity has been demonstrated within osteoid osteomas, which may explain why aspirin and other nonsteroidal anti-inflammatory drugs classically relieve the pain associated with these lesions. REFERENCES: Kneisl JS, Simon MA: Medical management compared with operative treatment for osteoid-osteoma. J Bone Joint Surg Am 1992;74:179-185. Unni KK: Dahlin’s Bone Tumors: General Aspects and Data on 11,087 Cases, ed 5. Philadelphia, PA, Lippincott-Raven, 1996, pp 121-130.

DISCUSSION: The "sunburst" radiographic appearance suggests an osteosarcoma, and the histologic findings confirm the diagnosis with malignant cells surrounded by pink osteoid. MRI scans are not particularly helpful in the diagnosis of osteosarcoma but are mandatory for surgical planning. Osteosarcomas are high-grade sarcomas that are best treated with chemotherapy and wide resection. Even though the peroneal nerve is involved, limb salvage is indicated. Survival after limb salvage is equivalent to amputation, with better function. REFERENCES: Goorin AM, Abelson HT, Frei E: Osteosarcoma: Fifteen years later. N Engl J Med 1985;313:1637. Link MP, Goorin AM, Miser AW, et al: The effect of adjuvant chemotherapy on relapse-free survival in patients with osteosarcoma of the extremity. N Engl J Med 1986;314:1600. Davis AM, Bell RS, Goodwin PJ: Prognostic factors in osteosarcoma: A critical review. J Clin Oncol 1994;12:423.

Osteosarcoma is the most common primary malignant bone tumor (5.6 per 1 million children younger than age 15 years), and Ewing’s sarcoma is second (2.1 per 1 million children). Giant cell tumor and chondrosarcoma are rare in children. Osteochondroma is more common than any of the above tumors in children, but it is not malignant.

DISCUSSION: Glomus tumors are rare vascular lesions typically occurring about the nail of the distal phalanx of the hand. The diagnostic “triad” of glomus tumors consists of local pain, sensitivity to cold, and paroxysmal pain. They tend to present with pain as the most typical symptom and this can be exacerbated by changes in temperature that is felt to cause a vascular response within the lesion. The biopsy specimen confirms a glomus tumor showing the typical vascular spaces surrounded by glomus epithelioid cells. REFERENCES: Zook EG, Brown RE: The perionychium, in Green DP, Hotchkiss RN, Pederson WC (eds): Green’s Operative Hand Surgery, ed 4. Philadelphia, PA, Churchill Livingstone, 1999, vol 2, pp 1353-1380. McDermott EM, Weiss AP: Glomus tumors. J Hand Surg Am 2006;31:1397-1400.

DISCUSSION: The biopsy specimens show a chondromyxoid fibroma with varying amounts of cartilage, benign fibrous tissue, giant cells, and loose myxoid areas. Chondromyxoid fibroma is a benign active bone lesion that is best treated with aggressive curettage and bone grafting. Although recurrences are common, more aggressive treatment is not warranted initially. REFERENCES: Wilson AJ, Kyriakos M, Ackerman LV: Chondromyxoid fibroma: Radiographic appearance in 38 cases and in a review of the literature. Radiology 1991;179:513-518. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 167-189.

DISCUSSION: The lesion is an aneurysmal bone cyst. These lesions are known to have a local recurrence rate of 5% to 50%. Young age, open physes, stage, and type of surgical removal and resulting margin have all been shown to affect the recurrence rate. Chemotherapy is not used in the treatment of aneurysmal bone cysts. REFERENCES: Gibbs CP Jr, Hefele MC, Peabody TD, et al: Aneurysmal bone cyst of the extremities: Factors related to local recurrence after curettage with a high-speed burr. J Bone Joint Surg Am 1999;81:1671-1678. Vergel De Dios AM, Bond JR, Shives TC, et al: Aneurysmal bone cyst: A clinicopathologic study of 238 cases. Cancer 1992;69:2921-2931.

DISCUSSION: Fibrous dysplasia frequently occurs in the proximal femur. Microfractures and remodeling can lead to the classic “Shepherd’s crook deformity.” The lesion has a ground-glass appearance on plain radiographs. The histologic appearance shows proliferating fibroblasts in a loose spindle cell background. Dysplastic metaplastic trabeculae are arranged in an irregular or “Chinese letter” appearance. REFERENCES: Enneking WF, Gearen PF: Fibrous dysplasia of the femoral neck: Treatment by cortical bone grafting. J Bone Joint Surg Am 1986;68:1415-1422. Simon MA, Springfield DS, et al: Common Benign Bone Tumors: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, pp 194-200.

DISCUSSION: The patient has severe acetabular protrusio, a condition that is frequently associated with Marfan syndrome. An echocardiogram is necessary to rule out the most serious consequence of this syndrome, aortic root widening, which can lead to aortic valve dysfunction or fatal aortic rupture. An electromyogram may be indicated for Charcot-Marie-Tooth disease, which is associated with acetabular dysplasia, but not protrusio. The renal ultrasound, the MRI scan, and the biopsy would be of no value in this patient. Protrusio can also be seen in patients with osteogenesis imperfecta and juvenile rheumatoid arthritis. REFERENCES: Steel HH: Protrusio acetabuli: Its occurrence in the completely expressed Marfan syndrome and its musculoskeletal component and a procedure to arrest the course of protrusion in the growing pelvis. J Pediatr Orthop 1996;16:704-718. Wenger DR, Ditkoff TJ, Herring JA, Mauldin DM: Protrusio acetabuli in Marfan’s syndrome. Clin Orthop 1980;147:134-138.

DISCUSSION: Although the classic radiographic appearance of fibrous dysplasia is one of a central metaphyseal lesion with ground glass matrix, it is not unusual to see either a more radiodense-appearing lesion or a more peripheral location. The histologic finding of spicules of woven bone without osteoblastic rimming in a bland fibrous background is diagnostic of fibrous dysplasia. The imaging studies could be consistent with low-grade osteosarcoma, osteoblastoma, or osteomyelitis, but all have a very different histologic picture. Observation is indicated in the absence of symptoms, impending fracture, or deformity. Fibrous dysplasia most commonly occurs in the proximal femur. REFERENCES: Huvos AG: Bone Tumors: Diagnosis, Treatment, and Prognosis. Philadelphia, PA, WB Saunders, 1991, pp 30-43. DiCaprio MR, Enneking WF: Fibrous dysplasia: Pathophysiology, evaluation, and treatment. J Bone Joint Surg Am 2005;87:1848-1864.

DISCUSSION: The radiographs show a lytic lesion in the right proximal tibia that has a high fluid content based on the MRI findings. The radiographic appearance is consistent with either telangiectatic osteosarcoma or aneurysmal bone cyst. Low-magnification histology shows a lesion resembling an aneurysmal bone cyst, with blood lakes separated by cellular septa. However, high-magnification shows severe cytologic atypia, indicative of a telangiectatic osteosarcoma. The appropriate treatment is neoadjuvant chemotherapy followed by wide resection and reconstruction of the lesion. 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. Arndt CA, Crist WM: Common musculoskeletal tumors of childhood and adolescence. N Engl J Med 1999;341:342-352.

DISCUSSION: The lesion is an osteochondroma. This is demonstrated by a pedunculated bone-forming lesion where the medullary space of the lesion communicates with the medullary space of the host bone. The cortex of the exostosis is in continuity with the cortex of the underlying bone. The MRI scan reveals that there is no significant cartilage cap, alleviating concern for malignant conversion to a chondrosarcoma. Osteoblastoma and osteosarcoma typically have mixed areas of bone formation and bone destruction. Malignant fibrous histiocytoma of bone is usually purely lytic. REFERENCES: Vaccaro AR (ed): Orthopaedic Knowledge Update 8. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2005, pp 197-215. Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 103-111.

DISCUSSION: The osseous sites most frequently involved by giant cell tumor of bone are the distal femur, proximal tibia, and distal radius with approximately 10% of giant cell tumors involving the distal radius. The goals of treatment are to remove the tumor completely and to preserve maximum function of the extremity. REFERENCE: Vander Griend RA, Funderburk CH: The treatment of giant-cell tumors of the distal part of the radius. J Bone Joint Surg Am 1993;75:899-908.