Four patients who developed malignant synovial tumours are described; one with chondromatosis developed a synovial chondrosarcoma and three with pigmented villonodular synovitis developed malignant change. The relevant literature is discussed.
Primary synovial pathology is almost always benign. The most commonly observed change is inflammation, but conditions such as synovial chondromatosis and pigmented villonodular synovitis are sometimes seen. Primary malignant synovial pathology is extremely rare. Over the last ten years in our specialist musculoskeletal tumour unit we have treated only four patients with primary malignant synovial tumours. We present their cases and review the literature.
An 81-year-old man presented with a six-month history of swelling and stiffness of his right knee. Clinical examination revealed a tender nodule in the popliteal fossa and a range of flexion of 60° to 90°. Radiographs and subsequent MRI showed ‘popcorn’ calcification consistent with synovial chondromatosis (Fig. 1⇓). A core biopsy of the lesion revealed an atypical chondroid neoplasm consistent with synovial chondromatosis. He underwent open debulking of the tumour through a posterior approach. A piecemeal excision was performed in order to preserve the popliteal neurovascular structures.
The specimen was examined by histopathology and was reported as atypical chondroid neoplasm. Initially he made a good postoperative recovery and the fixed-flexion deformity resolved, but within three months his swelling and stiffness had returned. Further radiographs and MRI confirmed local recurrence. Given the severity of his symptoms and the volume of the recurrent tumour, an above-knee amputation was performed. Histological analysis of the amputated limb confirmed the presence of a synovial chondrosarcoma (Fig. 2⇓).
CT of the chest revealed no pulmonary metastases. He was not given any adjuvant treatment and is alive and well six months after amputation.
Malignant pigmented villonodular synovitis
A 65-year-old man presented with pain and swelling of his left knee. Clinical examination revealed a firm mass 3 cm × 4 cm in size in front of the patellar tendon. He had a full range of movement. A core biopsy confirmed the diagnosis of pigmented villonodular synovitis with atypical features of focal necrosis and myxoid change. Local excision was performed, but this was intralesional since the tumour was adherent to the patellar tendon. Within three months he developed a local recurrence. He underwent a further excision with sacrifice of the patellar tendon because of recurrence and heavy involvement of the patellar tendon, and reconstruction with a gastrocnemius flap and split-skin graft. Histological analysis revealed a malignant spindle-cell tumour within pigmented villonodular synovitis with clear margins. Post-operatively, he was given radiotherapy (60 Gy). Two years later he presented again with swelling around the left knee and pain in the left hip associated with loss of weight. Clinical examination showed obvious recurrent tumour in the knee and further MR imaging revealed metastases in his pelvis and lungs. He had local radiotherapy to the pelvis and systemic treatment with Doxorubicin. He died two years and ten months after the initial diagnosis.
A 72-year-old woman presented with a four-year history of pain and intermittent swelling of the left knee. She had undergone arthroscopic debridement on four separate occasions with little benefit. Clinical examination revealed an effusion and a reduced range of movement. Plain radiographs showed early tricompartmental osteoarthritis and a well-defined lytic lateral femoral lesion. MRI showed diffuse, low-signal synovial thickening with erosion of the lateral femoral condyle extending into the patellofemoral joint. A core biopsy confirmed the diagnosis of pigmented villonodular synovitis. In view of the size of the bony lesion and its intra-articular extension she underwent an en bloc excision of the distal femur and endoprosthetic replacement. The histology of the resected femur confirmed the diagnosis of pigmented villonodular synovitis and showed its margins to be clear of tumour. She made a good recovery, regained a full range of movement and was able to walk unaided. Eight months later she presented again with pain and swelling of the thigh. MRI showed a lobular recurrent tumour surrounding the distal femur and extending into the muscles of the proximal thigh. CT of the chest showed no metastases to the lungs. An open biopsy confirmed malignant change in pigmented villonodular synovitis (Fig. 3⇓). She underwent a hip disarticulation. Histological analysis of the amputated limb confirmed malignant pigmented villonodular synovitis with clear margins. Six months later she is alive and well.
A 53-year-old woman presented with a swelling on the ulnar aspect of the right ring finger in its proximal part. It had been present for approximately five years. It had become gradually larger but caused no pain. On examination she had a normal range of movement in the fourth metacarpophalangeal and interphalangeal joints and neurological examination was normal. A clinical diagnosis of a ganglion was made and she underwent local excision. The histological diagnosis was thought to be a low-grade (Trojani grade I, low grade soft-tissue tumour) spindle-cell sarcoma with myofibroblastic differentiation and a positive margin. Two months later she presented again with further local swelling. Clinical examination revealed a nodule on the radial side of the flexor tendons overlying the proximal phalanx. MRI confirmed a local recurrence. She underwent a wide local excision although was given the option of disarticulation of the ring finger at the meta-carpophalangeal joint. Histological examination showed fibrous connective tissue including synovium containing a multinodular fibroblastic neoplasm. There was a fasciculate growth pattern of slightly atypical spindle cells. The lesion was considered to represent low-grade sarcomatous transformation of pigmented villonodular synovitis. The patient remains well eight months after her last operation.
In our unit over the last ten years we have treated 94 cases of synovial chondromatosis and 184 of pigmented villonodular synovitis. We have observed one case (1.06%) of malignant synovial chondromatosis and three (1.63%) of malignant pigmented villonodular synovitis. These four cases represent 1.43% of our case load which confirms that primary malignant synovial pathology is extremely rare.
Synovial chondromatosis is a benign neoplasm of synovial tissue. It most commonly affects the knee, but can affect any synovial joint. It is characterised by the presence of multiple cartilaginous bodies arising from the internal surface of the joint or from other structures lined by synovium.1 Its treatment is surgical, usually arthroscopic, removal of loose bodies, synovectomy or, more rarely, excision followed by joint replacement.2 The clinical and radiological features of synovial chondromatosis and synovial chondrosarcoma, whether primary or secondary, are the same. It is therefore difficult to distinguish between the two entities. Recurrence is not uncommon even after synovectomy. Histologically, synovial chondromatosis is characterised by cartilaginous metaplasia of the intimal layer of the synovial membrane in a solid matrix without myxoid change. In synovial chondrosarcoma the stroma shows myxoid change and the chondrocytes show marked cytological atypia.1,3,4 The most important feature favouring synovial chondrosarcoma is the permeation of bone. Although malignant change in synovial chondromatosis is well documented in the literature (Table I⇓),5–15 it is extremely rare.
In our case of synovial chondrosarcoma the tumour recurred after excision and required above-knee amputation. We believe that it was originally benign, but had undergone malignant transformation in some areas before the first operation. It is possible that the biopsy was unrepresentative of the areas which had undergone malignant transformation and therefore did not show this.
Pigmented villonodular synovitis commonly affects large joints such as the knee and hip but also any area of synovium. There are reports of cases involving the temporomandibular joint, the zygapophyseal joint and the calcaneonavicular, mid-tarsal and interphalangeal joints.16–18 The presentation is usually insidious and patients usually present months or years after the onset of symptoms with slowly progressive disease.
Histologically, pigmented villonodular synovitis is a benign condition of the synovial membrane and is presumed to be of histiocytic origin.19 Its cause is unknown. Jaffe, Lichtenstein and Sutro20 originally described its main histopathological features and proposed an inflammatory pathogenesis. Others19,21 believe that it is a neoplasm and this view is supported by chromosomal studies.11
Malignant pigmented villonodular synovitis is extremely rare. A review of the literature (Table I⇑) shows that there are only a few reported cases.22–28 The largest series of eight cases was reported by Bertoni et al22 in 1997. It may occur as a primary malignancy or may arise in an area of pigmented villonodular synovitis. It can be difficult to differentiate from benign aggressive pigmented villonodular synovitis. The pathological criteria currently used to diagnose malignant pigmented villonodular synovitis are a sarcoma arising within it or at the site of a previously diagnosed synovitis, or a synovial-based sarcoma with cytological features similar to sarcoma arising in a well-documented pigmented villonodular synovitis.
Histologically, malignant pigmented villonodular synovitis is characterised by a uniform proliferation of atypical round-to-spindle shaped cells arranged in sheets and fascicles (Fig. 3b⇑).
Multinucleate cells and foamy histiocytes are not typical features of malignant pigmented villonodular synovitis. Diffuse areas of ischaemic-like necrosis are generally present.
Most of the reported malignant cases19,22–29 had multiple local recurrences or wide bony metastases particularly those which had first been treated by local excision. More than half of these patients needed an amputation or more extensive surgery at a later date and also had pulmonary metastases. Local recurrence or metastatic disease may occur years after the initial presentation. It is therefore important that patients with synovial malignancy are followed up for a prolonged period. Amputation should be considered at the outset as a life-saving procedure rather than an attempt to salvage the limb.
Most cases of synovial disease are inflammatory or benign in nature. Our recent experience suggests that malignancy should be considered in patients with atypical symptoms. If there is any doubt about the diagnosis pre-operatively we recommend MRI and a core biopsy. If synovial malignancy involving a joint is confirmed then either an extra-articular resection or amputation is required. It is essential to achieve local control of these tumours since they are resistant to both radiotherapy and chemotherapy.
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
- Received November 27, 2006.
- Accepted June 11, 2007.
- © 2007 British Editorial Society of Bone and Joint Surgery