Rapidly progressive deterioration of renal function is a frequent but clinically unfavorable feature of anti-neutrophil cytoplasm autoantibody (ANCA)-associated vasculitis, including microscopic polyangiitis, Wegener's granulomatosis, and renal limited vasculitis1. Usually, this rapidly progressive deterioration of renal function is histopathologically accompanied by a pauci-immune crescentic necrotizing glomerulonephritis. However, the histopathological features vary among patients from mild focal segmental extracapillary proliferation to diffuse crescentic necrotizing glomerulonephritis with granulomas and tubular intra-epithelial infiltrates. In some cases, extensive glomerulosclerosis is found2.
The differences between microscopic polyangiitis and Wegener's granulomatosis have been described as follows3,4. Microscopic polyangiitis is characterized by a non-granulomatous systemic vasculitis that is associated, in a majority of cases, with ANCA positivity in a cytoplasmic (C-ANCA, 
25%) or perinuclear (P-ANCA, 60%) staining pattern, as determined by indirect immunofluorescence5. Sera that produce the C-ANCA pattern nearly always react with proteinase-3 (PR3-ANCA). The major P-ANCA target is myeloperoxidase (MPO-ANCA). Wegener's granulomatosis is characterized by a granulomatous systemic vasculitis with upper airway involvement that is associated, in a majority of cases, with C-ANCA positivity (65%) in the presence of PR3-ANCA, or P-ANCA positivity (20%) in the presence of MPO-ANCA5. Renal limited vasculitis is distinguished from microscopic polyangiitis and Wegener's granulomatosis by the absence of extrarenal symptoms of vasculitis. Despite these relatively clear disease descriptions, a diagnosis for the individual patient may be difficult to establish in clinical practice. Currently, patients are treated similarly, irrespective of their diagnosis. Whether diagnosis-specific modulation of therapy is needed, is unclear. This issue needs to be addressed. Knowledge of the differences in renal histopathology between these three diseases is relatively limited, though distinct differences may help to establish a more certain diagnosis and may give insight into the pathogenesis of ANCA-associated systemic vasculitis.
Clinically, vasculitic syndromes overlap, and diagnoses sometimes may be uncertain. Therefore, differentiation between the vasculitic syndromes by means of ANCA test results is sometimes preferred, which may be supported by the possible pathogenic role of ANCAs in pauci-immune crescentic necrotizing glomerulonephritis in relation to ANCA-associated vasculitis, and by the observation that meaningful differences between patients with various ANCA test results exist6. Differences in renal histopathology between patients with different ANCA test results were investigated but led to contradictory results (abstract, Bajema IM, J Am Soc Nephrol 8:532A, 1997)7,8,9.
Within the framework of the European Vasculitis Study group (EUVAS; see Acknowledgments), we prospectively gathered renal biopsies with clinical information of a large and homogeneous group of patients with renal disease in relation to ANCA-associated vasculitis. These conditions enabled us to perform the present study in which we determined (1) differences in the occurrence of renal histological lesions between microscopic polyangiitis, Wegener's granulomatosis, and renal limited vasculitis; and (2) differences in the occurrence of renal histological lesions between patients with ANCA-associated vasculitis with various ANCA test results.
METHODS
Patients
Patients in the present study were derived from two of the first-wave trials of the EUVAS10: CYCAZAREM, a randomized trial of cyclophosphamide versus azathioprine during remission of ANCA-positive systemic vasculitis10, and MEPEX, a randomized trial of adjunctive therapy for severe glomerulonephritis in ANCA-associated systemic vasculitis that examined plasma exchange versus intravenous administration of methylprednisolone10. Patients only were included into the present study if a renal biopsy, performed at study entry, was available. Inclusion criteria for CYCAZAREM and MEPEX are listed in Tables 1 and 2, respectively. Exclusion criteria for both trials included age under 18, pregnancy, previous malignancy, known HIV positivity, administration of any cytotoxic drug within a year before entry, and hepatitis B antigenemia (only if HepB-ag positive). An additional exclusion criterion for CYCAZAREM was serum creatinine> 500 
mol/L. Additional exclusion criteria for MEPEX were serum creatinine <500 mol/L, life-threatening non-renal manifestations of vasculitis, including alveolar hemorrhage requiring mechanical ventilation within 24 hours of admission, on dialysis for more than two weeks prior to referral, significant baseline renal impairment (creatinine> 200 mol/L, one year or more before presentation), or a previous episode of biopsy-proven necrotizing and/or crescentic glomerulonephritis10.
Renal histopathology
Paraffin sections were stained with silver, periodic acid-Schiff (PAS), hematoxylin & eosin (H&E), and trichrome, and were forwarded to two of five participating pathologists (IMB, LHN, FF, RW, JAB). Both pathologists scored the biopsies separately, blinded to patient data and the scores of the other observer, and according to a previously standardized protocol for scoring renal biopsies of patients with ANCA-associated systemic vasculitis11,12. In short, each glomerulus had to be scored separately on the presence of fibrinoid necrosis, crescents (cellular/fibrous and segmental/circumferential), glomerulosclerosis (local/segmental/global), periglomerular infiltrates, granulomatous reactions, as well as a number of other lesions. The presence of glomerular lesions was calculated as the percentage of the total number of glomeruli in a biopsy. Most interstitial, tubular and vascular lesions were scored as present or absent, except for interstitial infiltrates (-/+/++/+++), interstitial fibrosis (-/+/++) and tubular atrophy (-/+/++), which were scored semiquantitatively. Together, 39 histological parameters were examined. The scores were entered into a central database (MSAccess) and discrepancies between the observers were resolved by conference during central reviews, achieving consensus for each biopsy.
Immunofluorescence for immunoglobulins and complement components, and electron microscopy were performed locally in all participating centers. For logistical reasons, these procedures were not standardized or reviewed by the EUVAS, but the local conclusions were reported.
Diagnosis
Meeting the inclusion criteria was needed to enter patients in either CYCAZAREM or MEPEX. Diagnostic categories were distinguished (always with respect to the inclusion criteria, Tables 1 and 2) by the following criteria10 and as such determined by the local physicians, without review by the EUVAS:
Microscopic polyangiitis: Systemic vasculitis, predominantly affecting small vessels, with extrarenal symptoms, but without airway symptoms compatible with Wegener's granulomatosis.
Renal limited vasculitis: Idiopathic rapidly progressive glomerulonephritis without systemic disease manifestations.
Wegener's granulomatosis: Inflammation of the respiratory tract together with necrotizing vasculitis affecting small- to medium-sized vessels.
ANCA testing
Indirect immunofluorescence (IIF) and ELISA were performed for local ANCA testing in all participating centers. The staining pattern in the IIF test was scored as perinuclear (P-ANCA), cytoplasmic (C-ANCA), atypical, or negative. Sera positive for ANCA directed against MPO and PR3 were reported as MPO-ANCA and PR3-ANCA, respectively. To determine the different patterns of renal lesions in ANCA test subgroups, the ANCA test results also were classified as a combination of the IIF and ELISA results, as the specificity of ANCA testing increases by using this combination, compared to IIF or ELISA alone5.
Statistics
Differences of quantitative parameters between groups were assessed with the t test for independent samples. Differences of semiquantitative results were tested by using the Mann-Whitney U test. Difference of gender between groups was analyzed by the chi-square test.
RESULTS
Patients
Renal biopsies were performed in 132 of 157 patients that were recruited in CYCAZAREM. As a renal biopsy was an inclusion criterion for MEPEX, a renal biopsy was performed in all 124 patients in this study. Of the combined 256 biopsies from these two studies, 180 were received for re-evaluation. Seven of these 180 biopsies were excluded: five biopsies because of the absence of cortical tissue, and two because patients appeared to have antibodies directed against the glomerular basement membrane. Together, 173 biopsies (98 from CYCAZAREM and 75 from MEPEX) were available for evaluation in the present study. Patient diagnoses (as defined in the Methods section) were microscopic polyangiitis (N = 80), renal limited vasculitis (N = 19), and Wegener's granulomatosis (N = 73). The diagnosis of one patient remained uncertain (doubt about whether extrarenal manifestations were attributable to vasculitis). ANCA test results are listed in Table 3. The mean age of all patients was 59 years (range 21 to 83 years). Patients with MPO-ANCA were older than patients with PR3-ANCA (63 vs. 58 years, P = 0.033). Patients included 56% females and 44% males. The gender distribution was comparable in the various groups. Mean serum creatinine and GFR of all patients were 453 mol/L and 31 mL/min, respectively. Patients with microscopic polyangiitis and renal limited vasculitis had a significantly lower mean GFR than patients with Wegener's granulomatosis (20 and 22 vs. 44 mL/min, P < 0.001). Patients with a P-ANCA IIF had a significantly lower mean GFR than patients with a C-ANCA IIF (21 vs. 40 mL/min, P < 0.001). Patients with MPO-ANCA had a significantly lower mean GFR than patients with PR3-ANCA (21 vs. 38 mL/min, P = 0.002).
Histological diagnoses
Figure 1 shows the histopathological diagnoses on the basis of the renal biopsy findings. Crescentic necrotizing glomerulonephritis was observed in 112 biopsies (65%); crescentic glomerulonephritis without fibrinoid necrosis was present in 40 cases (23%). Two biopsies showed interstitial vasculitis only, one biopsy was normal, and nine biopsies (5%) showed diffuse global glomerulosclerosis. Other biopsies included focal global glomerulosclerosis, interstitial fibrosis, and mesangial matrix increase.
Figure 1.
Histopathological diagnoses on the basis of the renal biopsy findings.
Full figure and legend (68K)Histological parameters in all patients
The histological findings in the entire patient cohort showed that a mean of 29% of glomeruli per biopsy were normal, 45% of glomeruli had (predominantly cellular) crescents, and 23% were globally sclerotic. Fibrinoid necrosis of the glomerular tuft was present in 22% of glomeruli. In five biopsies fibrinoid necrosis was present in glomeruli without crescents, although crescents were found in other glomeruli in the same biopsy. Interstitial edema was present in 34% of biopsies. Interstitial infiltrates were present in 92% of biopsies; in half of those scored as mild (+), in the other half as severe (++). Mononuclear inflammatory cells were always present, and usually, they formed the predominant part of the infiltrates. Neutrophils were present in 65% of biopsies, but predominant in only a few cases. Although eosinophils were seen in 22% of biopsies, they were never scored as predominant. Interstitial fibrosis was present in 83% of biopsies and in approximately half of those cases it was scored as diffuse (++). Tubular casts and tubular necrosis were present in 87% and 66% of biopsies, respectively. Tubular atrophy was present in 86% of biopsies and in approximately one third of those cases was scored as diffuse (++). Tubular intra-epithelial infiltrates were seen in 64% of biopsies. Interstitial vasculitis was present in only 12% of biopsies. Arteriosclerosis and arteriolosclerosis were present in 70% and 32% of biopsies, respectively. Pauci-immunity was concluded in all patients. Electron microscopy was performed in some patients, but histopathological conclusions remained unchanged with this procedure.
Differences between diagnoses
Table 4 shows the mean percentage of the main glomerular parameters in microscopic polyangiitis, renal limited vasculitis, and Wegener's granulomatosis. In microscopic polyangiitis, 21% of glomeruli per biopsy were normal, whereas in Wegener's granulomatosis 40% of glomeruli were normal (Figure 2a, P < 0.001). Glomerulosclerosis was present in 30% of patients who were diagnosed with microscopic polyangiitis versus only 16% of patients with Wegener's granulomatosis (Figure 2a, P = 0.002). The percentage of glomeruli with fibrinoid necrosis or crescents did not distinguish between the diagnoses. In microscopic polyangiitis, interstitial fibrosis Figure 2b and tubular atrophy Figure 2c were more frequently and severely present than in Wegener's granulomatosis (P < 0.001 for both differences). Interstitial infiltrates Figure 2d and tubular necrosis Figure 2e tended to occur more frequently in microscopic polyangiitis than in Wegener's granulomatosis (P = 0.030 and P = 0.035, respectively). Tubular casts were more often reported in microscopic polyangiitis than in Wegener's granulomatosis (P = 0.005). However, there were no differences in proteinuria between the diagnostic groups (data not shown). Arteriosclerosis was present more often in microscopic polyangiitis than in Wegener's granulomatosis (P = 0.021). No difference was observed in the occurrence of interstitial vasculitis. Biopsies from the 19 patients with renal limited vasculitis were more or less comparable to those from the patients with microscopic polyangiitis (Table 4 and Figure 2).
Figure 2.
Renal histology in patients with microscopic polyangiitis, renal limited vasculitis, or Wegener's granulomatosis. Differences in presence of glomerular lesions (A), interstitial fibrosis (B), tubular atrophy (C), interstitial infiltrates (D), tubular necrosis (E), and tubular intra-epithelial infiltrates (F), between the diagnostic categories are presented. Symbols in panel A are: (
) other; (
) sclerosis; (
) crescents; (
) normal glomeruli. Symbols in panels B and C are: () diffuse; () focal; () absent. Panel D symbols are: () very dense; () dense; () mild; () absent. Symbols in panels E and F are: () present; () absent.
Differences between MPO-ANCA and PR3-ANCA
The distribution of histological parameters among the ELISA test result groups is presented in Table 5. The mean percentage glomerulosclerosis was 15% in patients with PR3-ANCA, 25% in patients with MPO-ANCA, and 35% in patients with negative ELISA test results (P = 0.022 for the difference between PR3-ANCA and MPO-ANCA, P = 0.005 for the difference between negative test results and PR3-ANCA; Figure 3a). The occurrence of fibrinoid necrosis and crescents was similar in all groups. In patients with MPO-ANCA positivity, interstitial fibrosis Figure 3b and tubular atrophy Figure 3c were more frequently and more severely present than in patients with PR3-ANCA positivity (P = 0.008 and P = 0.013, respectively). Tubular necrosis Figure 3e, tubular intra-epithelial infiltrates Figure 3f, and arteriosclerosis were more frequently present in patients with MPO-ANCA than in patients with PR3-ANCA (P = 0.030, P = 0.006, and P = 0.027, respectively). The histopathology in the group of patients with negative ELISA test results was more or less similar to that of MPO-ANCA positive patients (Table 5 and Figure 3). It is questionable whether these results are independent of the diagnostic subgroup. To address this issue, we tested whether ANCA specificity influenced renal histology independently of diagnosis. The observed differences in the occurrence of tubular necrosis (P = 0.021) and tubular intra-epithelial infiltrates (P = 0.005) between MPO-ANCA and PR3-ANCA positive patients remained significant after this correction. No differences between the groups were observed in the occurrence of interstitial vasculitis. We also investigated the distribution patterns of histological features in patients with P-ANCA versus patients with C-ANCA, and of P- and MPO-ANCA–positive patients versus C- and PR3-ANCA–positive patients. Results of these analyses were similar to the above-described histological distribution patterns in patients with MPO-ANCA versus patients with PR3-ANCA (data not shown).
Figure 3.
Renal histology in patients with PR3-ANCA, MPO-ANCA, PR3- and MPO-ANCA, or negative ELISA. Differences in presence of glomerular lesions (A), interstitial fibrosis (B), tubular atrophy (C), interstitial infiltrates (D), tubular necrosis (E), and tubular intra-epithelial infiltrates (F) between the ELISA test result groups are illustrated. Symbols in panel A are: () other; () sclerosis; () crescents; () normal glomeruli. Symbols in panels B and C are: () diffuse; () focal; () absent. Panel D symbols are: () very dense; () dense; () mild; () absent. Symbols in panels E and F are: () present; () absent.
Table 5 - Main glomerular lesions in patients with MPO-ANCA, PR3-ANCA, double positivity, and negative ELISA.
Full table Sample size
Reported results are based on analyses without a minimum for the number of glomeruli in the biopsies (biopsies without cortical tissue were excluded). We tested whether the presence of only a small number of glomeruli—less than five and less than ten—would influence our results, but this was not the case (data not shown).
DISCUSSION
We present the results of a prospective multicenter study of 173 renal biopsies from a homogeneous group of patients with newly diagnosed renal disease in relation to ANCA-associated vasculitis. Our aim was to determine (1) the differences in the occurrence of renal histological lesions in microscopic polyangiitis, Wegener's granulomatosis, and renal limited vasculitis; and (2) the differences in the occurrence of renal histological lesions in patients with ANCA-associated vasculitis with various ANCA test results.
Glomerulosclerosis, interstitial fibrosis, tubular atrophy, tubular casts, and arteriosclerosis occurred more often and more pronounced in microscopic polyangiitis and renal limited vasculitis than in Wegener's granulomatosis. However, none of these lesions were specific for one of the diagnostic subgroups, which limits the role of renal histopathology in further sub-categorizing ANCA-associated vasculitis. Except for tubular casts, the above-mentioned lesions are representative of a chronic disease phase, reflecting the result of longer existing inflammation of the kidney, in which irreversible scars develop. So-called active lesions (such as tubular intra-epithelial infiltrates and glomerular crescents) did not discriminate between the three diagnostic subgroups. We believe that the explanation for these results is that in patients with microscopic polyangiitis and renal limited vasculitis, the diagnosis is established later than in patients with Wegener's granulomatosis. In over 90% of cases, Wegener's granulomatosis presents with upper airway or pulmonary symptoms, or both13, which probably reduces the patient's and doctor's delay. Alternatively, although such a mechanism is not known in vasculitis, our results could also indicate that, at the same time point after onset of the disease, patients with renal limited vasculitis and with microscopic polyangiitis may have developed more irreversible lesions in the kidney than patients with Wegener's granulomatosis. This may be explained by a faster progression of active lesions to chronic lesions in microscopic polyangiitis and renal limited vasculitis or, alternatively, by development of chronic lesions without the obligatory presence of active lesions. An argument in favor of the occurrence of the latter mechanisms would be that, after correction for the diagnostic delay, the observed differences in renal histology between the diagnoses are still present. Therefore, we re-analyzed our results by correcting for the diagnostic delay (by correcting for the GFR), but no significant differences were observed (data not shown).
In this study, ANCA positivity was present in 149 of 164 patients in which ANCA test results were reported. Patients with MPO-ANCA had significantly more glomerulosclerosis, interstitial fibrosis, tubular atrophy, and arteriosclerosis, but also significantly more tubular necrosis and tubular intra-epithelial infiltrates. In other words, a mixture of both chronic and active lesions was more abundantly present in patients with MPO-ANCA than in patients with PR3-ANCA. The observed differences between the occurrence of tubular necrosis and tubular intra-epithelial infiltrates remained significant after correction for diagnosis. One should realize, however, that the observed differences are small, that none of the lesions is specific for one of the groups, and that active glomerular lesions (that is, fibrinoid necrosis and cellular crescents) were present to the same extent. Our results may be explained by the finding that circulating soluble MPO, released by activated polymorphonuclears, may bind to resting "innocent bystander polymorphonuclears," thereby making them reactive to anti-MPO antibodies, which leads to perpetuating inflammation and tissue destruction14. In addition, anti-MPO antibodies may inhibit the inactivation of MPO by ceruloplasmin, its natural inhibitor15, resulting in persistent generation of reactive oxygen radicals with enhanced potential for endothelial cytotoxicity16. These processes may lead to a more active disease, and in the long term, to more chronic damage in MPO-ANCA positive patients than in PR3-ANCA-positive patients. The previously reported tendency to a more frequent renal involvement in patients with MPO-ANCA than in patients with PR3-ANCA is further evidence for a stronger renal pathogenic effect of MPO-ANCA compared to PR3-ANCA12,17.
Previous investigations on the occurrence of renal histopathological differences between patients with MPO-ANCA and PR3-ANCA led to contradictory results. In three reports, no differences between these groups were found (abstract; ibid)7,8. Franssen et al described in a retrospective analysis of 36 patients with ANCA-associated vasculitis, that patients with PR3-ANCA positivity had more fibrinoid necrosis and a higher activity index than MPO-ANCA positive patients, and that patients with MPO-ANCA had more glomerulosclerosis and a higher chronicity index9, which may be explained by the inhibitory effect by PR3-ANCA binding to PR3 on the irreversible inactivation of PR3 by 
1-antitrypsin18, similar to the mechanism by which MPO-ANCA inhibits inactivation of MPO by ceruloplasmin19,20. In addition, the respiratory burst following activation of tumor necrosis factor- (TNF-) primed neutrophils in vitro by PR3 may be more potent than activation by MPO21, though this difference is not evident in other reports22,23,24.
It seems that, although differences exist between PR3-ANCA– and MPO-ANCA–associated vasculitis6, current knowledge on the mechanisms by which these ANCAs are involved in the pathogenesis of vasculitis is insufficient for the explanation of these differences. Alternatively, the action of ANCA is just an epiphenomenon.
In summary, we conclude that glomerulonephritis in relation to microscopic polyangiitis has more characteristics of chronic injury at the time of presentation than glomerulonephritis in relation to Wegener's granulomatosis. We suggest that this difference is due to a delayed establishment of diagnosis in patients with microscopic polyangiitis compared to patients with Wegener's granulomatosis. The finding that both active and chronic lesions are more abundantly present in MPO-ANCA-positive patients than in patients with PR3-ANCA positivity may be an argument in favor of the existence of different routes in the pathogenesis of renal disease in these ANCA subsets, although the mechanism remains unclear. In addition, our results suggest that ANCA test results may be useful in further classifying ANCA-associated vasculitides. Within the framework of the EUVAS, the phenotype of patients with systemic disease, differentiation of the leukocyte infiltration, and the predictive value of the renal histopathological parameters in this patient cohort will be investigated in the near future.
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Acknowledgments
The EUVAS group was supported by grants from the EU (Contract nos. BMH1-CT93-1078, CIPDCT94-0307, BMH4-CT97-2328, and ERBIC20-CT97-0019).
The following investigators participated in the European Vasculitis Study Group (EUVAS): Co-ordinator and project leader: N. Rasmussen (Rigshospitalet, Copenhagen, Denmark). Co-project leader: D.R.W. Jayne (Addenbrooke's Hospital, Cambridge, UK). EUVAS Members: I. Neumann (Wilhelmina Hospital, Vienna, Austria), D. Abramowicz (Erasmus Hospital, Bruxelles, Belgium), Ph. Madhoun (Edith Cavell Medical Institute, Bruxelles, Belgium), J. Sennesael (Academic Hospital of the Free University, Bruxelles, Belgium), V. Tesar, I. Rychlik, J. Bartunkova, J. Lukás (Charles University Hospital, Prague, Czech Republic), B. Ravn Juhl, J. Petersen, C.B. Andersen, and W. Szpirt (Rigshospitalet, Copenhagen, Denmark), A. Wiik (Statens Serum Institut, Copenhagen, Denmark), H. Løkkegaard, H. Nielsen (Herlev County Hospital, Denmark), T. Ring (Aalborg Hospital, Aalborg, Denmark), S. Freiesleben Sørensen (Bispebjerg Hospital, Bispebjerg, Denmark), P.A. Bacon, A. Exley, C.O.S. Savage (University Hospital Birmingham, Birmingham, UK), G. Gaskin, C. Pusey (Hammersmith Hospital, London, UK), C.M. Lockwood† (Addenbrooke's Hospital, Cambridge, UK), R. Luqmani (Western General Hospital, Edinburgh, UK), C. Grönhagen-Riska, A. Ekstrand (Helsinki University Hospital, Helsinki, Finland), L. Guillevin, F. Lhote (Hôpital Avicenne, Bobingy, France), Ph. Lesavre, L.H. Noël, P. Landais (Hôpital Necker, Paris, France), Ph. Vanhille (Centre Hospitalier de Valenciennes, Valenciennes, France), P. Bataille (Centre Hospitalier General, Bologne sur Mer, France), V. Esnault (CHU Hotel Dieu, Nantes, France), F. van der Woude, R. Waldherr, W. Schmitt, K. Andrassy, O. Hergesell, R. Nowack (Heidelberg University Hospital, Heidelberg, Germany), K. de Groot, K. Herlyn, W.L. Gross (Rheumaklinik, Bad Bramstedt, Germany), K.A. Boki, J.N. Boletis (Laikon General Hospital, Athens, Greece), D.S. Emmanouel (University Hospital Crete, Heraklion, Greece), C. Feighery (Saint James's Hospital, Dublin, Ireland), F. Ferrario, R.A. Sinico (Ospedale San Carlo Borromeo, Milan, Italy), G. Gregorini (Spedale Civili, Brescia, Italy), J. Dadoniené (University Hospital Vilnius, Vilnius, Lithuania), E.C. Hagen (Eemland Hospital, Amersfoort, The Netherlands), C.G.M. Kallenberg, C. Stegeman (University Hospital Groningen, Groningen, The Netherlands), J.W. Cohen Tervaert (University Hospital Maastricht, Maastricht, The Netherlands), C.A. Verburgh, C.E.H. Siegert, J.A. Bruijn, H.A. Hauer, J. Hermans, J.C. van Houwelingen, C.E. Vergunst (Leiden University Medical Center, Leiden, The Netherlands), E. van Gurp (University Medical Center Utrecht, Utrecht, The Netherlands), I.M. Bajema (Dijkzigt Hospital, Rotterdam, The Netherlands), C. Vasconcelos (Hospital San António, Porto, Portugal), E. Mirapeix, M. Solé (Hospital Clinic I Provincial, Barcelona, Spain), E.E. Pettersson, A. Bruchfeld (Huddinge University Hospital, Huddinge, Sweden), K.W.A. Westman (University Hospital of Lund, Lund, Sweden), Z. Heigl (Karolinska Hospital, Stockholm, Sweden), C. Chizzolini (University Hospital Geneva, Geneva, Switzerland), D. MacLahan (University Hospital, Basle, Switzerland). Pathologists who provided biopsy material: M. Depierreux (Academic Hospital of the Free University, Bruxelles, Belgium), B. van Damme (University Hospital Leuven, Leuven, Belgium), A. Stejskalová, Z. Vernerová (Charles University, Prague, Czech Republic), T. Törnroth (University of Helsinki, Helsinki, Finland), A.C. Feller (University of Luebeck, Luebeck, Germany), E. Gaffney (Saint James's Hospital, Dublin, Ireland), R. Tardanico (Ospedale Civili, Brescia, Italy), R. Consalonieri (Ospedale Maggiore CA Granda, Milan, Italy), G. Garibotto (ISUL, Genova, Italy), A.T.M.G. Tiebosch (Academic Hospital Groningen, Groningen, The Netherlands), C.D. Kooijman (Eemland Hospital, Amersfoort, The Netherlands), M. Sole Arques (Hospital Clinic I Provincial de Barcelona, Barcelona, Spain), F. Algaba (Puigvert, Barcelona, Barcelona, Spain), M. Carreras (Hospital de Bellvitge, Barcelona, Spain), M. Vaquero Perez (Hospital Universitari Germans Trias I Pujol, Badalona, Spain), L. Bernardo (Hospital Dr. Josep Trueta, Girona, Spain), B. Sundelin (Karolinska Hospital, Stockholm, Sweden), P. Alm (University Hospital of Lund, Lund, Sweden), A. Wernersson (Huddinge University Hospital, Sweden), B. Veress (University Hospital Malmø, Malmø, Sweden), W. Landells (Saint Helier Hospital, London, UK), A.J. Howie (University Hospital Birmingham, Birmingham, UK), S. Fleming (University Department of Pathology, Edinburgh, UK), A.P. Griffith (Morriston Hospital, Swansea, UK), P.N. Furness (Leicester Area Histopathology Service, Leicester, UK), H.T. Cook (Hammersmith Hospital, London, UK).
