J. clin. Path., 1976, 29, 17-21
A cause of erroneous diagnosis of pigmentedvillonodular synovitisR. A. BURNETT
From the University of Glasgow, Department ofPathology, Western Infirmary, Glasgow Gil 6NT
sYNoPsis An unusual type of benign vascular hamartoma, which shows a curious papillary organi-zation of thrombus and abundant haemosiderin deposition, is liable to be misdiagnosed histologic-ally as pigmented villonodular synovitis. Nine examples of this type of lesion are briefly presentedand the differential diagnosis is discussed.
Pigmented villonodular synovitis (PVNS) is anuncommon synovial lesion of uncertain nature whichis locally invasive and shows a propensity for recur-rence after surgical excision. It may involve articular,bursal or tendon sheath synovium either diffuselyor in a nodular form. The finger and hand are byfar the commonest areas to be affected (Wright,1949) and at these sites the lesion is almost invariablyof the nodular type (Byers et al, 1968). PVNS mustbe distinguished from synovial sarcoma, othertumours containing giant cells, osteochondromatosis,and granulomatous inflammatory reactions involvingthe synovium. Reported here are nine cases of anuncommon type of vascular hamartoma, seven ofwhich were mistaken histologically for PVNS. Theselesions show an unusual papillary organization ofthrombus with much haemosiderin deposition. Thistype of organization has been described only oncebefore in the literature (Sevitt, 1973) and this sourceof diagnostic error has not previously been reported.
Material and Methods
Of the nine cases presented here, seven were erron-eously diagnosed as PVNS. Three of these cases (3,5, and 9) were referred for histological opinion fromother hospitals in the Glasgow area. The other fourcases (1, 2, 7, and 8) were recognized during areview of all the reported examples of PVNS in thedepartmental files of this hospital over the last 23years (table I). All four lesions occurred in either thefinger or the hand and represent a significant pro-portion of the total digital and hand PVNS lesionsreviewed over this period (69 cases). The other twocases (4 and 6), although originally diagnosed as
Received for publication 10 July 1975.
Site Number of Cases (Sex ratio M:F)
Diffuse Nodular Total
Finger and hand - 69 69(23:46)
Knee 5 7 12(3:2) (2:5)
Ankle 1 3 4(M) (2:1)
Foot - 2 2(1 :1)
Wrist - 1 1(F)
Hip - 1 1(F)
Total 6 83 89
Table I PVNS- Western Infirmary, Glasgow 1952-74
vascular hamartomata, are included here becausethey show identical clinical and histological features.All these specimens were examined using standardhistological tissue processing and staining techniques.
Clinical Features
The clinical features are shown in table II. In sevenpatients the lesion occuxrred in the finger or hand,but an identical histological picture was also seenin the tissue obtained from a lesion within the tricepsmuscle of a 14-year-old boy (case 3) and from asecond excision of a lesion in the calf muscles of a4-year-old girl (case 5). Although the secondspecimen from case 5 was misinterpreted as pig-mented villonodular synovitis, the original excisionhad shown a simple vascular hamartoma whichconsisted of large blood-filled spaces but containedno thrombus and hence no papillary pattern liableto be confused with PVNS.
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Case Sex Age Site of Lesion Duration of Max. Diameter Pain Original CommentSymptoms of Lesion Diagnosis
(Histological)
I F 35 L. second finger middle I month 10 mm Slight PVNS Cystic lesion in subcutaneousphalanx, palmar aspect. tissue, no attachment toRecurrence after 18 months- 20 mm Slight PVNS tendons. Re-excision after
18 months. Since then norecurrence after 20 years
2 M 26 L. fourth finger, middle 1 month 10 mm Slight on PVNS Soft, dark, cystic, vascularphalanx palmar aspect movement tumour
3 M 14 Within triceps muscle 6 months Small Intermittent PVNS No follow-up availableabove elbow joint
4 F 21 R. second and third 12 months 10 mm Recently VH Superficial, not attached tofingers web palmar became swollen tendons. No recurrence afteraspect and painful 1 year
5 F 4 Within gastrocnemius History of 20 mm None VH Primary excision incomplete.muscle minor trauma Fibrous capsule
4 monthspreviously
Recurrence after 18 months - 20 mm None PVNS6 F 62 L. third finger, terminal 3 months 15 mm None VH Subcutaneous, haemorrhagic
phalanx, lateral aspect lesion7 M 43 R. hand, palmar aspect History of 30 mm Tender PVNS Superficial to flexor sheath,
trauma 6 months no recurrence after 2 yearspreviously
8 M 29 R. thumb, distal phalanx 12 months 15 mm Only on PVNS Clinically 'mucous cyst'radial aspect gripping
9 F 67 Index finger 3 months 10 mm - PVNSfollowing aburn
Table II ClinicalfeaturesVH = vascular hamartoma
Pathology
These vascular hamartomata were all between 10 and30 mm in their largest diameter and tended to benodular. They often appeared cystic or haemorrhagicand had well-defined margins. Histologically theyconsisted of rather large, but irregularly shaped,vascular spaces. The walls of most of these spaceswere rather thickened and many contained a well-defined layer of smooth muscle, often sited imme-diately beneath the endothelium. Variable butusually scanty amounts of elastic tissue were alsoseen. The growth of fibroblasts and capillary bloodvessels into the thrombus, which was present inmany of these spaces, produced a papillary pattern,and adjacent granulation tissue contained numerous,poorly formed, slitlike, vascular channels (fig 1).Large amounts of haemosiderin were invariablypresent. The appearances of the thrombus in allthese cases are identical with the 'organic fragmenta-tion' type of organization of thrombus, originallydescribed by Sevitt (1973) in his account of canaliza-tion in venous thrombosis.
Discussion
The features that led to the confusion between thesevascular hamartomata and PVNS are threefold:
(1) The papillary pattern produced by theorganization of the more superficial part of thethrombus may simulate synovial villi (fig 2). How-ever, these projections are often more delicate anddo not usually contain blood vessels. The smallerones consist of pale-staining, almost acellularcollagen.
(2) The more solid parts of the granulation tissuewhich has replaced thrombus may contain manythin-walled, slitlike, vascular channels, and thesemay be mistaken for synovial clefts caused by thematting together of synovial villi (fig 3). The cellslining these spaces, however, are spindle-shapedand do not contain iron. The channels are smallerand more orderly in arrangement than the irregular,coarse, sponge-like pattern of villous matting.
(3) The lumina of the vascular channels compo-sing the hamartoma may also be misinterpreted assynovial surfaces, but there is often an incompletelayer of smooth muscle immediately beneath thelining cells, a feature which is not present in syno-vium. In spite of the vascularity of the synovium inPVNS, the presence of organizing thrombus on thesynovial surface is distinctly uncommon.Although abundant haemosiderin is present in
these lesions (fig 4), no giant cells or sheets ofxanthoma cells are seen. Except forthe haemosiderin-containing macrophages, there is a lack of the
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A cause of erroneous diagnosis ofpigmented villonodular synovitis 19
Fig 1 Low-powerview ofpart of thelesion in case 4.A distended vascularspace containingorganizing thrombusis shown. In severalareas a pronouncedpapillary pattern isevident, and moresld regions contain
numerous slitlikechannels. Severalcollapsed, vascular
ft. ~~~~~~~~spacesin directcontinuity with thethrombosed vesselare present at thebottom of thepicture.Haematoxylin and
(4 eosin x 20.
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R. A. Burnett
Fig 3 Case 6.Numerous slitlikevascular channels arepresent in this area
of organizingthrombus. Thisappearance mttay bemistaken for villousmatting. The wall ofthe vascular channel,cut rather obliquely,is seen at the top leftof the picture.HandE x 75
Fig 4 Case S (recurrence). Higher-power view of a similar area to that shown in figure 3. Muchhaemosiderin is present. H and E x 210.
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A cause of erroneous diagnosis ofpigmented villonodular synovitis
macrophage-type cells which form the main cellularcomponent of the PVNS lesion.
Neither the site of these lesions nor the youngage groups in which they occur is helpful in differen-tiating them from PVNS. Although the finger isone of the commonest sites for PVNS, the lesionthere is almost invariably of the nodular type (Byerset al, 1968), while these vascular hamartomata arelikely to be confused with the villous form.
While these points may be ofhelp in differentiatingbetween papillary organizing thrombus in a vascularhamartoma and PVNS, the single most importantfactor is an awareness of the necessity for makingsuch a distinction.
The author is indebted to Dr Mary E. Catto,Reader in Orthopaedic Pathology at the Universityof Glasgow, for her help in the preparation of thispaper.
References
Byers, P. D., Cotton, R. E., Deacon, 0. W., Lowy, M.,Newman, P. H., Sissons, H. A., and Thomson, A. D.(1968). The diagnosis and treatment of pigmented villono-dular synovitis. J. Bone Jt Surg., 50B, 290-305.
Sevitt, S. (1973). The mechanisms of canalisation in deepvein thrombosis. J. Path., 110, 153-165.
Wright, C. J. E. (1949). Rapid recurrence of a giant-cellsynovioma of tendon sheath. J. Path. Bact., 61, 271-274.
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