A 49-year-old Caucasian woman was referred to our center. She was known for years to have fibrous dysplasia in the left femur and tibia.
When she was 49 years old, an attempt was made to excise the fibrous dysplasia from the proximal femur. Extreme hemorrhaging complicated the operation. The attending orthopedic surgeon decided to refer the patient to our specialized center. At the time of her visit to our center, she complained about progressive pain in her left thigh and lower leg. Her clinical physical examination revealed soft swelling in the left quadriceps region.
Conventional X-rays of the left leg showed typical features of fibrous dysplasia in the proximal femur (Figure ) and the proximal tibia (Figure ) with ground glass appearance and a shepherd's crook deformity.
X-ray of the left femur. Anteroposterior plain film of the upper left leg with typical osseous changes consistent with fibrous dysplasia and shepherd's crook deformity.
X-ray of the left tibia. Anteroposterior plain film of the left tibia showing fibrous dysplasia.
Magnetic resonance imaging (MRI) of her left leg showed extensive fibrous dysplasia in the entire femur with expansive growth in the greater trochanter. The left proximal tibia also showed signs of fibrous dysplasia extending 20 cm distally from the tibial plateau. Four well-delineated, cyst-like, intra-muscular soft-tissue lesions were seen in the quadriceps region. Surgery was planned in two sessions. Prior to both operations, angiography and embolization of the pathologic vascularization in both the femur and the tibia were performed.
During the first operation, intra-lesional excision of the tumor of the left proximal femur was performed, followed by cryosurgery. A correctional osteotomy of the left hip was performed, followed by homologous bone transplantation and fixation with a proximal femoral nail. Because of a weakened femoral head, the femoral neck screw had to be stabilized with bone cement. Allograft bone chips were impacted to induce bone matrix. During the procedure, an incisional biopsy of the soft-tissue lesions in the quadriceps muscle was performed.
Three weeks later an intra-lesional excision of the fibrous dysplasia of the left tibia was performed, followed by cryosurgery and implantation of an massive allograft inlay in the tibia. The allograft was fixed with AO screws. During this procedure, the soft-tissue lesions in the quadriceps muscle were excised.
Microscopic examination of the bone lesions of both femur and tibia showed hypocellular fibrous tissue with irregular bone formations and without cytologic atypia compatible with fibrous dysplasia. In one lesion, the remnants of fracture callus were present (Figure ).
Histology of fibrous dysplasia of our patient. Photomicrograph showing curvilinear, slender trabeculae of woven bone surrounded by cellular fibroblastic tissue. There is no osteoblastic rim at the bone-stromal interface.
The soft-tissue lesions showed a paucicellular tumor with spindle-shaped or stellate not atypical cells embedded in a loose myxoid alcian blue-positive inter-cellular matrix with sparse capillary blood vessels. Confocal microscopy revealed a thin fibrous capsule at the tumor margin; however, at the interface with skeletal muscle, infiltration between the individual muscle fibers was evident, which is typical of intra-muscular myxomas (Figure ), proving the diagnosis of Mazabraud's syndrome in our patient.
Histology of myxoma of our patient. Photomicrograph showing a paucicellular myxomatous lesion with dispersed, inconspicuous spindle cells.
Post-operatively, the patient's treatment consisted of non-weight-bearing mobilization for three months in plaster of Paris. During follow-up, plain films were obtained at six-week intervals. Eventually, these images showed consolidation of the femur osteotomy and incorporation of the allograft.
Nine months post-operatively the patient developed progressive pain in the left thigh. Conventional X-rays showed protrusion of the femoral neck screw. Repositioning of the screw was performed. Her post-operative follow-up with X-rays obtained regularly (Figures and ) was satisfactory.
Figure 5 Anteroposterior X-ray of the whole left leg. Situation after fibrous dysplasia excision of the left proximal femur and left tibia with correctional osteotomy of the left hip and fixation with a proximal femoral nail, as well as allograft fixation with (more ...)
Lateral X-ray of the whole left leg. This X-ray shows the situation after fibrous dysplasia excision of the left proximal femur and left tibia.
Almost two years later the patient complained about a painless mass localized on the lateral side of the left knee. A solid mass was felt anterolaterally of the proximal tibia. Plain film radiographs did not show abnormalities; however, an ultrasound examination showed a homogeneous, hypoechogenic, soft-tissue mass with a cyst-like aspect. MRI showed a well-defined soft-tissue lesion in the lateral retinaculum and vastus lateralis muscle with a homogeneous high signal intensity on T2-weighted images and a homogeneous low signal intensity on T1-weighted images, consistent with fluid. A second intra-osseous lesion with an approximate diameter of 3 cm and the same signal characteristics and enhancement pattern was detected in the lateral tibial plateau (Figures and ).
Figure 7 T1-weighted magnetic resonance imaging scan of our patient. Axial spin echo T1-weighted pre-contrast magnetic resonance imaging (MRI) scan of the left knee reveals two well-delineated masses (arrows) with a homogeneous low signal intensity in the lateral (more ...)
Figure 8 T2-weighted MRI scan of our patient. This T2-weighted image shows identical thin rim enhancement and heterogeneous intra-lesional enhancement in both masses. These findings may suggest myxomatous masses. In contrast, fibrous dysplasia can be noticed in (more ...)
The lesions were considered to be a new soft-tissue myxoma and a relapse of fibrous dysplasia in the proximal tibia, respectively. Surgical excision of both lesions was performed without pre-operative biopsies, followed by cryosurgery and homologous bone implantation. A histopathological examination of the intra-muscular lesion showed a myxoma. As a unique finding, histopathological examination of the intra-osseous lesion in the lateral tibial plateau was consistent with myxoma as well (Figure ).
Histology of intra-osseous myxoma of our patient. Bone within a paucicellular myxoid lesion with small, bland spindle cells.
During follow-up, MRI of the patient's left leg was performed at regular intervals. These scans showed no signs of recurrence in the first post-operative years.
Three years after her last operation multiple tumors in her left upper leg were felt, which raised clinical suspicions of myxomas. MRI scans showed five new soft-tissue lesions consistent with characteristics of myxoma in the upper and lower leg regions. All lesions were marked ultrasonographically and excised, followed by cryosurgery. Histopathological examination of all intra-muscular lesions confirmed the diagnoses. Post-operatively the patient recovered gradually. Every three months ultrasonography of her left leg was performed, which showed no signs of myxoma until 2009. By then, she had developed several new intra-muscular myxomas, which were not treated. At her last follow-up examination in early 2010, our patient was in good condition. Several myxomas had developed but were found to be stable on the basis of MRI.