Giant cell tumor of the left ring ﬁnger metacarpal bone
Magnetic resonance imaging (MRI) showed a subarticular expansile lesion in the head of the ring ﬁnger metacarpal bone. On T1-weighted imaging, the lesion exhibited a inhomogeneous low signal intensity lesion. On short tau inversion recovery imaging, it had inhomogeneous high signal intensity. There was cortical destruction with soft tissue invasion that almost touched the middle ﬁnger metacarpal bone (Figure 2, A and B). The middle ﬁnger metacarpal bone showed the normal contour and signal. The extensor tendons were effaced and exhibited the normal signal, surrounded with the abnormal bright signal that involved subcutaneous fat. The overlying skin was normal. On the palmar side there was a tiny normal soft tissue plane between the ﬂexor tendons and the expansile process. The ﬂexor tendons were normal. The subcutaneous fat on this image appeared normal. The mass on the ulnar side touched the little ﬁnger metacarpal bone, which had normal contour and signal (Figure 2C). A whole-body bone scan and spot ﬁlms of the hands showed a single lesion in the skeleton located in the left hand (Figure 3).
Microscopic examination showed a tumor composed of numerous multi-nucleated giant cells admixed with the mononucleated stromal cells. The mono nucleated stromal cells were oval-shaped and lacked atypia, and their nuclei displayed features similar to those present within the giant cells (Figure 4).
Giant cell tumors comprise 4% to 5% of primary bone tumors and 18.2% of benign bone tumors. They usually occur in the 20- to 40-year-old age group (60% to 70% of tumors), although they may appear in older patients and in younger patients who have not yet ceased growing. The frequency of giant cell tumors is greater in women than in men. Giant cell tumors predominate in the long tubular bones (75% to 90% of cases). The distal portions of the femur, radius, and the proximal portion of the tibia are the most characteristic sites of involvement (approximately 50% of cases). Approximately 5% of giant cell tumors localize in the small bones of the hands or feet; more commonly, they are found in the hands. Although usually benign, 5% to 10% of these tumors are malignant. As in this case, 10% of patients have a pathological fracture. The predominant clinical features are nonspeciﬁc and include local swelling, warmth, and radiating pain.1 The symptoms may go on for months before becoming severe enough to demand clinical attention. Acute onset of pain is frequently associated with fractures, bringing the tumor to clinical attention.2
The pathology involves a predominance of giant cells, although this is not speciﬁc for the diagnosis. They are among mononuclear stromal cells, and fusion of the mononuclear cells leads to formation of the giant cells. They both have similar-appearing nuclei, a feature that aids in excluding other diagnoses.2 There is eosinophilic, granular cytoplasm surrounding the regularly outlined nuclei. Rarely are mitotic ﬁgures found within the giant cells. There may be bands of ﬁbrous tissue that have no giant cells present or osteoid foci within a fracture callus. Up to 40% of giant cell tumors show evidence of vascular invasion, a feature that is present in our case.3
The ﬁrst step in evaluation involves plain radiographs, on which there is a characteristic appearance. An eccentric, osteolytic lesion that is sub-articular in location is often seen. Giant cell tumors commonly appear radiolucent and do not show periosteal reaction.1 If the tumor is complicated by a fracture, there may be reactive bone formation. Some tumors may show areas of infarct or intravascular tumor emboli. Septa sometimes are seen and are caused by uneven tumor growth. Variation in appearance warrants more in-depth examination. A computed tomography (CT) scan shows ﬁndings similar to those seen on plain ﬁlms and often does not reveal additional information. MRI has a high diagnostic accuracy, especially if correlated with ﬁndings from X-ray and/or CT scanning.4 MR images can display the intraosseous, intra-articular, and soft tissue extension of the tumor. Typically, there is a large encapsulated soft tissue mass with low-to-intermediate signals on T1-weighted images. A T2-weighted image exhibits a homogeneous enhancement of medium-to-high intensity signal. Findings will depend on the amount of cystic, necrotic, or hemorrhagic material present. There may be inhomogeneous signal intensity or a poorly outlined tumor when this content is found.5
Deﬁnitive diagnosis is made with a biopsy. A patient who has a giant cell tumor should undergo a whole-body bone scan because 40% of patients will have giant cell tumors in other areas of the body. The differential diagnosis includes an eurysmal bone cysts, chondroblastoma, chondromyxoid ﬁbroma, giant cell reparative granuloma, nonossifying ﬁbroma, Langerhans’ cell histiocytosis, synovial sarcoma, and high-grade central osteosarcoma. These lesions have similar radiographic appearances.3,5
The treatment of choice for most giant cell tumors is intralesional “extended” curettage. Curettage alone is associated with recurrence in almost 50% of cases. To avoid recurrence, physicians have added adjuvant treatments such as liquid nitrogen, phenol, and high-speed burring.6 One study showed that the use of bisphosphonates may help reduce recurrence.7 After tumor removal, the space can be ﬁlled with polymethylmethacrylate cement or bone graft. Using cement with curettage allows weight-bearing quickly, but a recurrence can easily develop around the cement. Bone grafts may provide better movement and use of the joint area.6 In small bones, giant cell tumors tend to show a permeative growth pattern. This feature makes a complete evacuation of the tumor difﬁcult using only curettage. An en bloc resection with a bone graft has been recommended. When giant cell tumors recur and are benign, it usually is not fatal. With recurrence, it is imperative to do a detailed curettage with adjuvant therapy or joint-sparing surgery, if possible. With any giant cell tumor, follow-up on a regular basis is necessary.1
Giant cell tumors are relatively common bone tumors that are usually seen at the end of long bones in patients ≤40 years of age. They usually have grown to a large size upon discovery. They often show no host immune response and no matrix. Our case presents giant cell tumor in a rare location with internal trabeculation and aggressive features in a patient with a history of trauma. A healing pathologic fracture through an enchondroma or aneurysmal bone cyst can have a similar radiographic appearance and create diagnostic uncertainty. An additional consideration in this case would include the malignant alteration of enchondroma to chondrosarcoma, but this has not been reported in this location to our knowledge. Particular attention should be made to patients with fractures because this is a common presentation for giant cell tumors. It is important to evaluate both the clinical and radiologic ﬁndings, and proceed with a biopsy. As with this case, treatment is appropriate removal of the tumor. Recurrent tumor is always of concern and can be reduced by certain techniques.7