1 Clin Pathol 1996;49:164-167

Inflammatory pseudotumour of the mouth andmaxilla

A W H Shek, P C Wu, N Samman

AbstractAim-To describe the clinicopathologicaland immunophenotypical findings of twocases of inflammatory pseudotumour inthe oral cavity.Methods and Results-The patients pre-sented with a short history of swelling inthe cheek and the maxilla respectively.Magnetic resonance imaging or com-puterised tomography scan showed spaceoccupying lesions with infiltrative marginswhich were interpreted as aggressivemalignant neoplasms. Histological ex-amination showed fascicles ofspindle cellsin a background of chronic reactive in-flammatory cells including plasma cells,typical of inflammatory pseudotumour.The spindle cells were positive for vi-mentin, smooth muscle actin and CD68,but were negative for follicular dendriticcell markers. The lymphocytes showed nolight chain restriction.Conclusions-Inflammatory pseudotumourin the oral cavity is completely benign andsimple excision is curative. However, itmay be confused with a malignant tumouron clinical and radiographic grounds, andhistologically the appearances can also bemisinterpreted as those of a more ag-gressive lesion. Its correct recognition bythe surgical pathologist is important toavoid unnecessarily radical and potentiallymutilating surgery.(J Clin Pathol 1996;49:164-167)

Keywords: inflammatory pseudotumour, oral cavity,immunohistochemistry.

Case reportsCASE 1A 20 year old man was referred for a swellingover the right cheek. This had been present forone month and did not respond to antibiotictreatment. Physical examination revealed adiffuse swelling over the right cheek. Intra-orally, there was a firm exophytic mass of 2 cmdiameter in the right cheek opposite the molarregion. The overlying mucosa was ulcerated,but there was no discharge. Magnetic res-onance imaging (MRI) revealed an infiltrativelesion invading skin and parotid duct (fig 1).The impression was that of an aggressive neo-plasm.

Fine needle aspiration was performed andsmears showed non-specific chronic inflam-mation with epithelioid-like cells present (fig2). Special stains for micro-organisms, in-cluding mycobacteria and fungi, were negative.Excisional biopsy was advised.The lesion was completely excised and histo-

logical examination showed fascicles of elong-ated spindle cells in a mixed inflammatorybackground with a predominance of plasmacells (fig 3). Special stains for micro-organisms,including mycobacteria and fungi, werenegative. The majority of the spindle cellswere positive for CD68 (Dako) and vimentin(Dako), while a smaller number were positivefor smooth muscle actin (BioGenex), butthey were negative for S-100 (Dako),MAK-6 (Ciba), CD21 (Dako), Ber-MAC-DRC(Dako), and Ki-M4 (table 1). The lympho-

University of HongKong, Queen MaryHospital, Hong Kong:Department ofPathologyA W H ShekP C Wu

Department of Oraland MaxillofacialSurgeryN Samman

Correspondence to:Dr Tony W H Shek,Department of Pathology,University of Hong Kong,Queen Mary Hospital,Hong Kong.Accepted for publication:5 September 1995

Inflammatory pseudotumour is a tumour-likelesion characterised histologically by fascicles ofplump spindle cells in a background of chronicinflammatory cells, notably plasma cells. Othersynonyms have been used to describe similarlesions, such as plasma cell granuloma, histio-cytoma, xanthomatous granuloma, inflam-matory myofibroblastictumour, and spindle cellpseudotumour.

Inflammatory pseudotumour occurs in awide variety of somatic tissue and visceral or-gans, including the lung,' liver,2 thyroid,3 andmany other organs. Recently it has been des-cribed in the major salivary glands4 and thebuccal tissue in children.5 We describe herethe clinical, radiological, histological, and im-munophenotypical findings of two examples ofinflammatory pseudotumour in the oral cavityin adults.

Figure 1 MRI appearance of the firtn indurated mass(arrow) anterior to the right masseter muscle, infiltratingskin but not involving bone.

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.4

Figure 2 Clusters of mixed chronic inflammatory cells composed of histiocytes, Figure 4 CT appearance of cystic lesion within the leftlymphocytes, plasma cells, and some epithelioid cells (x 35). maxillary sinus, with erosion of the anterior wall of the

maxilla (arrow).

Figure 3 Short, swirling fascicles of spindle cells admixed with plasma cells andlymphocytes (x 114).

cytes and plasma cells showed no light chainrestriction.The patient was well at 13 months follow up

with no recurrence of tumour.

CASE 2A 36 year old woman was referred for man-agement of a painless, gradually enlargingswelling in the left maxilla for the past year.Physical examination revealed a small palpableswelling in the left infraorbital region with nor-

mal overlying skin. The eye movements werenormal. No epiphora or nasal discharge wasnoted.

Intraorally, a diffuse swelling in the left upperbuccal sulcus was present, extending from themidline to the maxillary tuberosity. The cov-ering mucosa was normal. The second pre-molar was tender to percussion but bothpremolars and the first molar on the left sidewere negative to electric pulp testing. Plainradiographs showed a loculated cystic lesionin proximity to the left maxillary teeth andextending into the left maxillary sinus. Therewas no root resorption. Computed tomography(CT) scan showed a cystic lesion occupying alarge part of the maxillary sinus with evidenceof erosion of the anterior wall of the sinus inthe infraorbital region (fig 4). It was interpretedas an aggressive neoplasm.Open biopsy through an intraoral sulcus in-

cision revealed a cystic cavity containing strawcoloured fluid with an irregular yellowish firmmass at its wall on the cheek. Histologicalexamination showed fibroblastic spindle cellsadmixed with abundant chronic inflammatorycells and focally the stroma was loose andmyxoid, closely resembling that of nodularfasciitis (fig 5). The lesion was entirely resected.Microscopic examination showed fascicles ofplump spindle cells with abundant plasma cellsand lymphocytes in the background, identicalwith that of case 1. Areas resembling nodularfasciitis found in the previous biopsy specimen

Table 1 Immunohistochemical profiles of the spindle cells in the two cases of inflammatory pseudotumourAntibody Source Major reactivity Results

Case 1 Case 2Smooth muscle actin BioGenex (San Ramon, CA, USA) Smooth muscle cell + (f) +CD68 Dako (Glostrup, Denmark) Histiocytes + + (f)Vimentin Dako Mesenchymal cells + +S-100 Dako Interdigitating cells, - -

melanocytic cells, etcMAK-6 Ciba (Alamendo, CA, USA) Epithelial cellsCD21 Dako Follicular dendritic cell -Ber-MAC-DRC Dako Follicular dendritic cell -Ki-M4 * Follicular dendritic cell -

(f) = focally positive.* Kindly donated by Prof M R Parwaresch, Kiel, Germany.

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Figure 5 Spindle cells in a myxoid background, resembling nodular fasciitis (x 240).

were not seen. Special stains for micro-organisms, including mycobacteria and fungi,were negative. The majority of these plumpspindle cells stained strongly for vimentin andsmooth muscle actin and only a minority was

positive for CD68. They were negative forS-100, MAK-6, CD21, Ber-MAC-DRC, andKi-M4 (table 1). Scattered CD68 positivemacrophages were found among the chronicinflammatory cells. The plasma cells and lym-phocytes showed no light chain restriction. Thecyst was lined by ulcerated, non-keratinised,stratified squamous epithelium with a fibroticwall, consistent with an infected residual cyst.The patient was well at 13 months follow up

with no recurrence of tumour.

DiscussionInflammatory pseudotumour of the oral cavityis very rare and only eight previous reportedcases are to be found in English language pub-lications (table 2). It occurs in a wide age range

(19 months to 63 years), but it tends to affectchildren and young adults. The cheek andthe mandible are the sites of predilection. Itpresents as an intraoral painless swelling ofrelative short duration, which is firm and in-durated on physical examination. Unlike itscounterpart in the visceral organs, oral in-flammatory pseudotumour does not producesignificant systemic symptoms, and routineblood investigations are normal. Magnetic res-

onance imaging or a CT scan was done in twoofthe reported cases and in both ofour patients.

All were characterised by infiltrative margins,and were interpreted on radiological groundsas aggressive malignant neoplasms.The cause of inflammatory pseudotumour

remains unknown and microbiological cultureresult is usually negative although Escherichiacoli has been found in an example of in-flammatory pseudotumour of the liver." Mor-phologically similar lesions caused by myco-

bacteria have been described in the skin,'2lymph node'3 bone marrow,'4 and lung'5 inimmunosuppressed transplant patients or

patients with acquired immunodeficiency syn-

drome. When it occurs in the mandible, in-

flammatory pseudotumour is usually associatedwith dental granuloma and in addition to thecharacteristic spindle cells there are also abund-ant foam cells, cholesterol clefts, and giantcells.67 Such concomitant presence of dentalgranuloma and a chronically inflamed cyst inour case 2 may lend support to the idea thatinflammatory pseudotumour is an unusual tis-sue reaction to chronic inflammation.

Histologically, inflammatory pseudotumourof the oral cavity is similar to that of otherorgans, although a nodular fasciitis-like area

has never been described. The proportion ofspindle cells, foam cells, lymphocytes, andplasma cells is highly variable, and Chen'6 re-

ported an increased proportion of foam cellsin a subsequent follow up biopsy specimen ina case of inflammatory pseudotumour of theliver. Furthermore the immunophenotype ofthe spindle cells is also highly variable; theplump spindle cells in case 2 were stronglypositive for vimentin and smooth muscle actinbut only weakly and sparingly positive forCD68, while in case 1 they were strongly posi-tive for CD68 and weakly positive for smoothmuscle actin and vimentin. This observation isconsistent with the concept that these spindlecells are of fibrohistiocytic nature, showing theimmunohistochemical phenotypes of bothhistiocytes and myofibroblasts."' A similar ob-servation has also been reported in in-flammatory pseudotumours of the majorsalivary gland4 and the liver.2 The spindle cellsin case 1 were more elongated and appearedepithelioid, which raises the possibility ofgranulomatous inflammation in cytologicalpreparations. The cytological features of in-flammatory pseudotumour have been de-scribed rarely.'8 '9 It is generally accepted thata definite cytological diagnosis of inflammatorypseudotumour cannot be made by fine needleaspiration cytology because the predominantcell pattern is non-specific. '8

Table 2 Summary of reported cases of oral inflammatory pseudotumourAuthor Sex Age Site Follow up data

Iiston et al' F 4 Right cheek No recurrence at 6 months19 m Left cheek No recurrence at 10 months

M 6 Right cheek ?Rudy et al6 F 49 Right lower jaw No recurrence at 10 monthsZegarelli et al' F 56 Mandible No recurrence at 1 yearAcevedo and Buhlert F 49 Gingiva ?Earl et aP M 44 Right mandible No recurrence at 2 yearsInui et allo M 63 Right mandible No recurrence at 2 5 yearsShek et al M 20 Right cheek No recurrence at 13 months(present study) F 36 Left maxilla No recurrence at 13 months

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Being a fibrohistiocytic lesion, inflammatorypseudotumour may be misinterpreted by thehistopathologist as being a neoplastic or quasi-neoplastic condition of the myofibroblasts,such as nodular fasciitis, fibromatosis, or fibro-sarcoma. The positive immunohistochemicalstain for actin in inflammatory pseudotumourcan be a potential diagnostic pitfall and itmay be mistaken as a leiomyosarcoma. Oralinflammatory pseudotumour needs to bedistinguished from the recently describedfollicular dendritic cell tumour of the oral cav-ity,20 which runs an indolent course with atendency of local recurrence. Nodular fasciitisuncommonly occurs in the oral cavity and it ischaracterised histologically by the presence ofloose myxoid matrix containing short linearcurved fascicles of spindle cells.2"22 Althoughfocal nodular fasciitis-like area was detected incase 2, inflammatory pseudotumour can bedistinguished by the presence oflonger fasciclesof spindle cells in an inflammatory backgroundrich in plasma cells. Fibromatosis of the oralcavity usually occurs in young adults and it ischaracterised histologically by broad interlacingfascicles of mature fibroblasts with a variabledegree of collagenisation.23 An inflammatorycomponent is absent. It is notoriously difficultto separate fibromatosis from well differ-entiated fibrosarcoma, especially in infants andjuveniles in whom fibromatoses are char-acterised by higher mitotic rates than in adults.Its distinction from inflammatory pseudo-tumour can be established by the absence of aninflammatory component. Follicular dendriticcell tumour of the oral cavity is a recentlydescribed entity which can closely mimic in-flammatory pseudotumour, with whorls or fas-cicles ofplump spindle cells in an inflammatorybackground of lymphocytes and histiocytes.20In contrast, plasma cells constitute a significantproportion of the chronic inflammatory cells ininflammatory pseudotumour. The distinctioncan be established by the positive staining forCD21, Ber-MAC-DRC, and Ki-M4 in fol-licular dendritic cell tumour.20

In conclusion, inflammatory pseudotumourofthe oral cavity is a distinct pathological entitycharacterised by fascicles of spindle cells in aninflammatory background rich in plasma cells.Clinically and radiographically it may be mis-interpreted as a malignant neoplasm. Cytologicdiagnosis on fine needle aspiration can rarelyreach a definitive diagnosis and excisional bi-opsy is usually required. Treatment is complete

surgical resection which is curative. No deathhas been ascribed to it when it occurs in theoral cavity. Its correct recognition by surgicalpathologists is, therefore, vital in order to avoidunnecessary extensive and radical surgery.We would like to thank ProfMR Marwaresch for giving us themonoclonal antibody Ki-M4.

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