10. Pathology and Oncology MCQs

Epithelioid sarcoma is the most common soft-tissue sarcoma in the hand and most commonly occurs in young adults. The tumors can be superficial and may become ulcerated. Deeper lesions are often attached to tendons, tendon sheaths, or fascial structures. These are usually minimally symptomatic. The biopsy specimen reveals the typical appearance of a nodular pattern with central necrosis. They can mimic a necrotizing granulomatous process. Usually there are chronic inflammatory cells along the margin of the tumor nodules. This biopsy specimen does not have the clear cells necessary for a clear cell carcinoma or sarcoma. Nora’s tumor is a bizarre parosteal osteochondromatous proliferation (BPOP) first described in 1983 by the pathologist, Nora. The lesion is defined as a reactive heterotopic ossification and is mostly found in the hands or feet of adults in the third decade of life.

Synovial sarcoma is the most common foot sarcoma. Frequently there is a delay in diagnosis because the lesions are rare. The lesions tend to occur in younger adults, typically between the ages of 15 and 40 years. In this patient, the tumor has grown to a substantial size and involves many of the bones of the midfoot. Limb salvage may be a possibility when incorporated into a multidisciplinary treatment program, but this will entail months of adjuvant treatment and significant morbidity. Amputation and early prosthetic fitting still have a role in management of some soft-tissue sarcomas, most frequently in the foot.

DISCUSSION: The clinical presentation, imaging, and biopsy findings (epithelial-like cells in clusters) are diagnostic of metastatic bone disease. Treatment for metastatic bone disease depends on the primary site, the patient's systemic status, and the stability of the lesion.

Primary synovial chondromatosis is a benign neoplastic/metaplastic condition in which the synovial membrane undergoes metaplasia to form cartilaginous nodules. These nodules can detach, become loose bodies, and subsequently calcify or ossify. They are typically uniform in size, unlike secondary synovial chondromatosis (due to osteoarthritis or trauma), where loose bodies are usually fewer and of varying sizes.

Pigmented villonodular synovitis (PVNS), also known as tenosynovial giant cell tumor, is a benign but locally aggressive synovial proliferative disorder. It presents with recurrent monoarticular hemarthrosis. The classic MRI finding is low signal intensity on T1 and T2 weighted images with a prominent 'blooming artifact' on gradient-echo (GRE) sequences due to the paramagnetic effects of hemosiderin deposition.

Fibrous dysplasia in the femoral neck frequently warrants treatment because of the risk of pathologic fracture. Cortical strut grafts reduce the risk of local recurrence compared with cancellous bone grafting. Because of the consequences associated with fracture in this location, prophylactic fixation is recommended. Radiation therapy and chemotherapy are not used for this benign condition.

DISCUSSION: Multiple hereditary exostosis and enchondroma commonly present as multiple lesions in the hand. Multiple hereditary exostosis consists of cartilage capped bony exostoses arising from the metaphyseal end of rapidly growing bones. Osteosarcoma and chondrosarcoma rarely appear as multiple lesions. Fracture callus can exhibit enchondral ossification that is usually circumferential, but the radiographic findings are not consistent with fracture. REFERENCES: Porter DE, Emerton ME, Villanueva-Lopez F, Simpson AH: Clinical and radiographic analysis of osteochondromas and growth disturbance in hereditary multiple exostoses. J Pediatr Orthop 2000;20:246-250. Pierz KA, Stieber JR, Kusumi K, Dormans JP: Hereditary multiple exostoses: One center’s experience and review of etiology. Clin Orthop 2002;402:49-59.

DISCUSSION: Nodular fasciitis is a benign soft-tissue lesion that usually arises from the fascia and is often misdiagnosed as a sarcoma. Desmoid tumors (aggressive fibromatosis) are also benign tumors with a greater tendency for local recurrence. Desmoid tumors have more spindle-shaped fibroblasts in an abundant collagenous matrix. Malignant fibrous histiocytoma is a hypercellular pleomorphic sarcoma more commonly found in adults. The histology is not consistant with a fatty tumor. REFERENCE: Bernstein KE, Lattes R: Nodular (pseudosarcomatous) fasciitis, a nonrecurrent lesion: Clinicopathologic study of 134 cases. Cancer 1982;49:1668-1678.

DISCUSSION: Ewing’s sarcoma typically can occur in the diaphysis of the long bones (50% to 55%). It is often accompanied by a large soft-tissue mass. Abnormal findings are common, including a low-grade fever, an elevated ESR, and leukocytosis. The histology is consistent with a small round blue cell tumor. The unique pathology and other findings exclude osteosarcoma. Giant cell tumor and chondrosarcoma have a different histologic appearance and typically are more metaphyseal in location.

Pigmented villonodular synovitis (PVNS) is a synovial proliferative disorder that remains a diagnostic difficulty. The most common clinical features are mechanical pain and limited joint motion. On radiographs, the classic finding is often a large lesion, associated with multiple lucencies. Other findings may include a normal radiographic appearance, loss of joint space, osteonecrosis of the femoral head, or acetabular protrusion. MRI is the imaging modality of choice and will show the characteristic findings of a joint effusion, synovial proliferation, and bulging of the hip. The synovial lining has a low signal on T1- and T2-weighted images, secondary to hemosiderin deposition. Copper deposition occurs in patients with Wilson’s disease, which mainly affects the liver.

The findings are consistent with an aneurysmal bone cyst. The MRI scan demonstrates a lesion involving the posterior elements of the vertebrae with fluid-fluid levels and neural compression. Fibrovascular tissue with multinucleated giant cells surrounding a vascular lake is seen on the histology. The most appropriate treatment is a marginal resection of the involved posterior elements. Although the recurrence rate can be as high as 25% to 30%, wide surgical resection could result in permanent neurologic injury and is not necessary. Aspiration and steroid injection have been advocated but would not relieve the nerve compression in this patient. Radiation therapy and chemotherapy are not indicated.

DISCUSSION: The patient has a fracture through a unicameral bone cyst, as evidenced by the “falling leaf” sign on the radiograph. Following healing of the fracture, treatment should consist of corticosteroid injection or bone marrow injection. Some cysts heal with the fracture and do not require injections. Biopsy is unnecessary because the radiograph shows that the cyst is benign. Curettage and bone grafting are seldom necessary because these cysts regularly heal with injections. Corticosteroids are useful when injected into the cyst, but are not used systemically. Pulsed electromagnetic fields have not been used therapeutically in this condition. REFERENCE: Yandow SM, Lundeen GA, Scott SM, Coffin C: Autogenic bone marrow injections as a treatment for simple bone cyst. J Pediatr Orthop 1998;18:616-620.

DISCUSSION: Unlike malignant bone tumors, malignant soft-tissue tumors usually are asymptomatic and present with the presence of a mass. Malignant soft-tissue tumors enlarge by centrifugal growth, creating a mass while compressing surrounding tissue. Symptoms may develop as the result of direct compression on neurovascular structures as the tumor enlarges. This is especially true in the pelvis where the tumor can enlarge appreciably without being noticed. However, in the extremities, the tumor is most often apparent before neurologic symptoms develop. An asymptomatic mass is not necessarily benign; therefore, biopsy should not be delayed. It is uncommon for a malignant soft-tissue mass to be discovered incidentally. Soft-tissue tumors are not typically apparent on radiographs; they are best identified with MRI. REFERENCES: Brouns F, Stas M, De Wever I: Delay in diagnosis of soft tissue sarcomas. Eur J Surg Oncol 2003;29:440-445. Rougraff B: The diagnosis and management of soft tissue sarcomas of the extremities in the adult. Curr Probl Cancer 1999;23:1-50. Sim FH, Frassica FJ, Frassica DA: Soft-tissue tumors: Diagnosis, evaluation, and management. J Am Acad Orthop Surg 1994;2:202-211.

DISCUSSION: The patient has a pathologic fracture of the right distal femur; therefore, given the patient’s age, the most likely diagnosis is metastatic carcinoma. Staging studies should be obtained prior to surgical treatment. Immediate intramedullary fixation is contraindicated before a diagnosis is made by biopsy. Surgical stabilization should be performed prior to radiation therapy. REFERENCE: Rougraff BT, Kneisl JS, Simon MA: Skeletal metastases of unknown origin: A prospective study of a diagnostic strategy. J Bone Joint Surg Am 1993;75:1276-1281.

Most authors have agreed that radiation therapy should be avoided in the treatment of giant cell tumor, as there is a high prevalence of sarcomatous degeneration.

The patient has a unicameral bone cyst. Because the subtrochanteric part of the femur is a high-stress region, the treatment of choice is bone curettage and grafting.

Nodular fasciitis is a pseudosarcomatous, self-limiting reactive process composed of fibroblasts and myofibroblasts. It is most commonly seen in adults who are 20 to 40 years of age. Histologically, the lesion is composed of predominantly plump, immature-appearing fibroblasts that bear a close resemblance to the fibroblasts found in granulation tissue.

A periosteal desmoid lesion is a tumor simulator characterized by a bone irregularity along the posteromedial aspect of the distal femur. These lesions are asymptomatic and are frequently an incidental finding. Observation is the management of choice.

The history, clinical photograph, and ultrasonography evaluation point to a diagnosis of ganglion cyst. The likelihood of resolution of ganglion cysts without intervention in pediatric patients ranges from 66-79%. Therefore the most appropriate treatment at this time is observation. Because the diagnosis is confirmed with the information provided, excisional biopsy and further imaging are not necessary.

Synovial herniation pits or Pitt’s pits are tumor simulators and are incidentally identified on radiographs obtained for either pain or trauma. The main diagnostic pitfall with this lesion is mistakenly identifying it as an osteoid osteoma. Accurate diagnosis is achieved by knowledge of the location and the characteristic imaging appearance. These are common lesions in individuals with femoroacetabular impingement.