Pigmented villonodular synovitis: light and electron microscopic studies

Pigmented villonodular synovitis of the knee in a patient on oral anticoagulation therapy: a case report

INTRODUCTION

Pigmented villonodular synovitis is a disease which affects the synovial joints and tendon sheaths. Although the exact aetiological factors are not known, we believe that recurrent haemarthrosis has a role in the aetiology of this condition.

CASE PRESENTATION

A 62-year-old Caucasian man presented with gradually worsening pain and stiffness in his right knee. The patient was on anticoagulation therapy and had been treated for recurrent episodes of spontaneous haemarthrosis of the knee. The International Normalized Ratio on each occasion suggested poor control of the anticoagulation therapy. A diagnosis of pigmented villonodular synovitis was made based on intra-operative findings and was further confirmed by a histopathological examination.

CONCLUSION

This report is presented to highlight the unusual association of haemarthrosis and pigmented villonodular synovitis.

Wegener's granulomatosis and giant cell tumor of tendon sheaths: casual or causal combination? First case report

Giant cell tumor of tendon sheath (GCTTS) and Wegener's granulomatosis (WG) are rare conditions both characterized by polyclonal cellular proliferation and multinucleated giant cells formation. Here, we report the case of a 27-year-old Caucasian woman affected by WG who experienced the metachrone appearance of two different GCTTSs at the right hand within a time of 3 years. To our knowledge, the combination of GCTT with WG is exceptional and this could probably be the first case reported. The subsequent appearance of two rare diseases both characterized by giant cell formation apparently points to similarities in their pathogenesis. However, at present no pathogenic relationship between GCTTS and WG is demonstrable and their simultaneous occurrence has to be considered coincidental. Actually, an emerging opinion is to consider GCTTS as a mixed lesion in which both tumoral and non-tumoral inflammatory cells play a central pathogenic action. On this view, the proposed case could support the evidence about the crucial role of a chronic inflammatory injury in enhancing GCTTS appearance.

Long-term follow-up of surgically treated localized pigmented villonodular synovitis of the knee

PURPOSE

The purpose of this study was to review a single institution's large consecutive series of localized pigmented villonodular synovitis (PVNS) of the knee.

METHODS

Cases for review were identified by a search of our institution's pathology records for definitive diagnoses of monoarticular localized PVNS (LPVNS) of the knee between 1970 and 1996. Patients' presenting symptoms and examination were recorded, as were the preoperative diagnosis and documentation of the PVNS nodule's location in the knee at surgery. Eighty-four patients were diagnosed with localized PVNS of the knee during the study period. Twenty-nine of these cases were incidental findings associated with planned total knee replacement and were excluded from the study. Of the remaining 55 patients constituting the study subgroup, 26 have been reviewed in detail.

RESULTS

There were 15 males and 11 females, and the mean age at presentation was 36.7 years. Patients presented for evaluation at an average of 15 months after the onset of symptoms. Pain was the most common complaint, reported by 24 of the 26. Locking and giving way were reported by 10 and 5 patients, respectively. On examination, 13 patients had an effusion, 11 had joint line tenderness, and 10 had a palpable mass. The most common preoperative diagnosis was a meniscus tear (10 of the 26), followed by PVNS (4), "mass" (4), and anterior cruciate ligament injury (3). At surgery, the nodule of PVNS was found most frequently in the suprapatellar pouch (6 cases), followed by the femoral notch (4), lateral synovium/gutter (4), popliteal fossa (3), lateral compartment (3), and medial compartment (2). Fourteen of the procedures performed were open, and 12 were performed by arthroscopy. Ten of the 26 patients participated in a long-term follow-up via the Lysholm Knee Scoring Scale questionnaire (average, 65.8 months postoperatively; average score, 95.4/100). Of these 10, 7 returned for follow-up clinical examinations (6 excellent results and 1 good). All 10 patients were operated on arthroscopically, and none required repeat surgery.

CONCLUSIONS

This review represents the largest series of localized PVNS of the knee to date. Echoing the findings of other PVNS studies, patients presented, on average, in their fourth decade. The common preoperative diagnosis of a meniscal tear is not surprising given the frequent presentation of a painful and, typically, locking knee with joint line tenderness and effusion. Interestingly, what is perhaps the most diagnostic finding on examination, a palpable mass, was present in only 1 of the 6 patients who had PVNS in the most common location, the suprapatellar pouch. With the ease and utility of modern arthroscopy, however, PVNS is an easily treatable condition that can be diagnosed at the time of surgery.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Increased expression of humanin peptide in diffuse-type pigmented villonodular synovitis: implication of its mitochondrial abnormality

OBJECTIVES

To define the pathogenesis of pigmented villonodular synovitis (PVNS), by searching for highly expressed genes in primary synovial cells from patients with PVNS.

METHODS

A combination of subtraction cloning and Southern colony hybridisation was used to detect highly expressed genes in PVNS in comparison with rheumatoid synovial cells. Northern hybridisation was performed to confirm the differential expression of the humanin gene in PVNS. Expression of the humanin peptide was analysed by western blotting and immunohistochemistry. Electron microscopic immunohistochemistry was performed to investigate the distribution of this peptide within the cell.

RESULTS

68 highly expressed genes were identified in PVNS. Humanin genes were strongly expressed in diffuse-type PVNS, but were barely detected in nodular-type PVNS, rheumatoid arthritis, or osteoarthritis. Humanin peptide was identified in synovium from diffuse-type PVNS, and most of the positive cells were distributed in the deep layer of the synovial tissue. Double staining with anti-humanin and anti-heat shock protein 60 showed that humanin was expressed mainly in mitochondria. Electron microscopy disclosed immunolocalisation of this peptide, predominantly around dense iron deposits within the siderosome.

CONCLUSIONS

Increased expression of the humanin peptide in mitochondria and siderosomes is characteristic of synovial cells from diffuse-type PVNS. Humanin is an anti-apoptotic peptide which is encoded in the mitochondrial genome. Present findings suggest that mitochondrial dysfunction may be the principal factor in pathogenesis of diffuse-type PVNS and that humanin peptide may play a part in the neoplastic process in this form of PVNS.

Quantitative photometrical assessment of iron deposits in synovial membranes in different joint diseases

We investigated 86 synovial membranes from patients suffering either from rheumatoid arthritis (RA) or osteoarthritis (OA). Iron deposits in the synovial membrane were stained by the Prussian blue reaction, and the amount of stained iron was quantitatively assessed by microscope photometry. We found a statistically significant increase in iron deposits in the synovial membrane of RA patients when compared to OA patients. The amount of iron deposits correlated with the histological subtype of synovitis, those presenting with more exudative and proliferative features showing greater amounts of iron deposits. We also observed an inverse correlation between the haemoglobin concentration and erythrocytes in the serum and the amount of iron in the synovial membrane. From our data we concluded that iron deposits in the synovial membrane can contribute by several mechanisms, including activation of oxygen radicals, to the chronic inflammatory reaction in RA synovitis.

Expression of metalloproteinases in pigmented villonodular synovitis

Pigmented villonodular synovitis (PVNS) is an idiopathic proliferative synovial process composed of two predominant cell types: mononuclear histiocytic cells and giant cells. This lesion can be locally invasive and can result in bone cyst formation and late cartilage and bone loss. Because metalloproteinases have been implicated in the joint destruction occurring in inflammatory arthritis and in the ability of certain tumors to invade adjacent tissues, their presence in PVNS was determined. Synovial tissue samples were collected at surgical synovectomy from the knees of 10 patients with a prior histological diagnosis of PVNS. Pigmented villonodular synovitis synovium was examined for the presence of the metalloproteinases collagenase and stromelysin. Messenger RNA (mRNA) for collagenase and stromelysin was present in all patient samples, although in varying amounts. In situ hybridization studies on synovial tissue sections identified synovial lining cells as the predominant cells expressing these metalloproteinases. Occasional infiltrating mononuclear histiocytic cells also were producing metalloproteinase mRNA. Giant cells did not express mRNA for the metalloproteinases collagenase and stromelysin. These results suggest that collagenase and stromelysin may be among the mediators of cartilage and bone loss that can occur in PVNS.

Treatment of pigmented villonodular synovitis with yttrium-90: changes in immunologic features, Tc-99m uptake measurements, and MR imaging of one case

Pigmented villonodular synovitis (PVNS) is an uncommon proliferative disease of synovium. We report a 35-year-old male with diffuse form of PVNS of left knee, treated with intraarticular injection of 5 mCi of yttrium-90 (Y-90) silicate colloid consisting of two doses with a 3-month interval between them. During follow-up, the affected knee showed clinical improvement and was accompanied by a decrease of the levels of soluble interleukin-2 receptor in sera and synovial fluids (SF). When compared to osteoarthritis subjects, SF lymphocyte subsets of this case before Y-90 therapy showed a lower CD4:CD8 cell ratio and absence of suppressor inducer cells (CD4+ 2H4+). The Tc-99m pertechnetate knee uptake indexes correlated well with clinical improvement. Serial magnetic resonance imaging revealed significant change one year after Y-90 therapy. The findings of immunological assessment suggested that immunoregulatory dysfunction may be related to the pathogenesis of PVNS.

Treatment of pigmented villonodular synovitis of the knee with yttrium-90 silicate: prospective evaluations by arthroscopy, histology, and 99mTc pertechnetate uptake measurements

The diffuse form of pigmented villonodular synovitis of eight knee joints of eight patients was treated by intra-articular injection of 185 MBq yttrium-90 silicate (90Y). Six patients had a recurrence of disease after one or two surgical synovectomies. After treatment with 90Y once or twice four knees showed clinical improvement with an accompanying decrease of the inflammatory activity as measured by the technetium-99m pertechnetate (99mTcO4-) uptake ratio and the severity of the diseased synovial tissue. Arthroscopy was performed before and six months after each 90Y treatment. The ratio of 99mTcO4- uptake in the inflamed compared with the normal knee joint correlated well with the macroscopical grading of pigmented villonodular synovitis. In all cases areas of persistent synovitis were found after the 90Y injection and this was confirmed both by histological examination and 99mTcO4- uptake measurements. Biopsy specimens taken from the diseased synovial areas showed histologically mostly less prominent and less numerous villi. The cartilage damage was slightly increased in only two cases. No radiological deterioration was found during follow up (mean 24 months, range 12-41). No complications of the radiosynoviortheses were noted.

Relationship between iron deposits and tissue damage in the synovium: an ultrastructural study

A detailed ultrastructural study was made of the synovial iron deposits in cases of haemophilic synovitis (HS), pigmented villonodular synovitis (PVNS), rheumatoid arthritis (RA), osteoarthritis (OA), seronegative inflammatory arthritis (SNA), and in controls, to investigate the relationship between iron deposits and tissue damage. Iron was seen by electron microscopy in about 75% of synovial lining cells in HS and PVNS but only in about 25% of synovial cells from cases of RA and SNA. In cases of OA and in controls iron deposits were scarce. The iron was usually deposited within pleomorphic siderosomes and in HS was most common in type A synovial cells. In contrast, deposits in all other cases were more common in type B cells, which were frequently the predominant cell type, and siderosomes were smaller, more homogeneous, and were more common in deeper synovial tissue. Considerable tissue damage was noted in the vicinity of iron rich siderosomes in synovial A cells from cases of HS, but such deposits in B cells in the synovium from the other cases had relatively little effect. We discuss the possibility that such differences directly reflect the differing functions of type A and B synovial cells, and particularly their relative ability to produce metabolically active oxygen metabolites with tissue destructive potential in the presence of iron.