AMELOBLASTIC FIBROMA--CASE REPORT

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1 AMELOBLASTIC FIBROMA--CASE REPORT J. R. TROTT, M.D.S.(Adelaide) Associate Professor of Oral Pathology, University of Manitoba, Faculty of Dentistry, Winnipeg 3, Canada INTRODUCTION NEOPLASIA of the odontogenic tissues is rare and, in recent years, there has been an attempt to understand the'. nours by a classification founded on the primary tissue of origin (Blackwood, I. Thus they can arise either from the odontogenic epithelium or mesenchyme, and in turn the former group may or may not have an inductive change on the mesoderm. If it does, then we are faced in the case of the ameloblastic fibroma with a true mixed tumour. Such entities as the compound and complex odontomes although containing mixed tissue could, with some justification, be considered hamartomata and not neoplasia. Argument on these points no doubt will continue until a sufficient amount of histological material is accumulated and analysed by more sophisticated methods. The present lesion is reported simply because there are few reported cases of this kind in the literature. Gorlin et al. (I96r) revealed only 23 such cases at that time, and also to impress upon practitioners the need for histological examination of material which might in the usual course of events be disposed of as 'granulation tissue'. CASE REPORT Clinical Findings. The patient, a girl aged 85 years, attended her dentist for a regular six-monthly check in April I965. The dentist had for the last year been observing whether the a/was going to be resorbed and exfoliated normally. However, at this visit the a/ was still present, vital and only slightly mobile so that a periapical film of the area was taken. During the year that the patient had been under observation, the normal eruption of the permanent teeth had taken place with the exception of the I/. There was no abnormal swelling in the buccal sulcus above a/, neither was the area tender to palpation nor the deciduous tooth sensitive to percussion. Radiographic examination showed the normal eruption of/r and 2/ while a/ lay superficially in the alveolar bone (Fig. I). The periodontal space and the laminadura was normal around the remaining root of a/ and at least half to two-thirds of the deciduous root had been resorbed. Apical to t-he lamina dura around the a/a radiolucent area extended from the mesial of 2/to the mesio-incisal angle of the unerupted r/and apparently involved part of the crown at the disto-incisal angle. The radiolucent area measured approximately 9 8 ram. The periapical radiolucency was diagnosed as an incisive canal cyst and the a/was extracted without difficulty using local anaesthesia. The dentist, however, found the patient 'very apprehensive' and decided to refer the patient to an oral surgeon for curettage of the radiolucent area. Under general anaesthesia, a flap was laid back on II

12 BRITISH JOURNAL OF ORAL SURGERY the buccal aspect of the unerupted tooth, the overlying bone removed and the soft 'granulation' tissue curetted and sent for histological examination.

in diameter, were submitted for histological examination. FIG.

2 12 BRITISH JOURNAL OF ORAL SURGERY the buccal aspect of the unerupted tooth, the overlying bone removed and the soft 'granulation' tissue curetted and sent for histological examination. At operation, the surgeon reports that the lesion was only 3 mm. in diameter. Three irregular small pieces of soft white tissue, each approximately 2 mm. in diameter, were submitted for histological examination. FIG. I Periapical view of the a/ showing the intact lamina dura around the apex of a/and the radiolucent area over the crown of the unerupted I/and bctween these two teeth. Histological Findings. Histologically, the tissue showed three pieces of soft tissue and several small spicules of bone. In only one of the soft tissue pieces was there evidence of a 'mixed' tumour. This consisted of an oval piece of tissue (Fig. 2A) with a definite boundary, but only in one area was there any arrangement of collagen fibres to form a capsule. The remainder of the tissue showed mainly a primitive mesenchymal tissue with multiform nuclei of the constituent cells and a fine fibrillar meshwork, similar to a developing dental papillae. Near one pole of the lesion there was a clump ofodontogenic epithelial cells arranged in a dumbell formation. These cells were mostly cuboidal in nature, irregularly arranged both peripherally and centrally, with no sign of a stellate reticulum. Around the periphery of this clump of epithelial cells there was a halo effect from a condensation of a homogeneous eosinophilic material which was largely cell free (Fig. 2B). No active mitoses were observed in any of the 50 sections examined either in the mesenchyme or the odontogenic epithelia. Because of the predominance of the irregular mesenchymal tissue which had many of the appearances of primitive pulp tissue and the presence of the odontogenic epithelium which showed both cuboidal and columnar cells, a diagnosis of ameloblastic fibroma was made. In an attempt to clarify the nature of the mesenchymal tissue in this odontogenic tumour, a Massons trichrome, PAS, reticulin and mucicarmine stain were used on the sections. Sections from umbilical cord, contro sections and sections taken from a developing tooth germ were stained similarly. The reticulin stain showed a fine interlacing network of branching fibrils with the occasional formation of collagen bundles within the lesion (Fig. 3A). A similar picture could be seen with the Massons trichrome, mucicarmine (Fig. 3, B and c) and the PAS However, with the later two stains the open spaces in the network did not show a positive reaction.

AMELOBLASTIC FIBROMA--CASE REPORT 13 T h e halo effect seen in the H. and E.

mesenchymal tissue. Stain H. and E., orig. mag. 60. FIG. 3A T u m o u r showing the fine reticular network. Stain Wilder's Reticulin.

3 AMELOBLASTIC FIBROMA--CASE REPORT 13 T h e halo effect seen in the H. and E. stained sections surrounding the clumps of odontogenic epithelium was not particularly conspicuous with the connective tissue stains that were used. FIG. 2B FIG. 2B Part of the lesion at higher magnification showing the odontogenic epithelium, the halo effect around it and the primitive mesenchymal tissue. Stain H. and E., orig. mag. 60. FIG. 3A T u m o u r showing the fine reticular network. Stain Wilder's Reticulin. Orig. mag. x i5 o. FIG. 3B Turnout showing the fine fibrillar structure, lack of ground substance staining and the loss of the halo effect around the odontog.enic epithelium. Stain mucicarmine. Orig. mag. x I5O. FIG. 3c Same lesion. Stain PAS. Orig. mag. I5o. (Note the lack of staining of the ground substance.)

14 BRITISH JOURNAL OF ORAL SURGERY DISCUSSION Lesions such as this are interesting because of their possible histogenesis particularly when two elements, ectodermal and mesodermal comprise the lesion.

They do not state the stain used to confirm this appearance and certainly their Figure 3 shows such a situation but it could be a photomicrograph of an H. and E. section.

4 14 BRITISH JOURNAL OF ORAL SURGERY DISCUSSION Lesions such as this are interesting because of their possible histogenesis particularly when two elements, ectodermal and mesodermal comprise the lesion. Chaudhry et al. (I962) describes a lesion where there were large areas of myxomatous tissue. They do not state the stain used to confirm this appearance and certainly their Figure 3 shows such a situation but it could be a photomicrograph of an H. and E. section. Willis (I96O) is quite clear that only with the demonstration of mucin can one justify the claim that in a presumed fibroma or fibrosarcoma are there myxomatous changes. It is possible in this lesion that this is either an oedematous fibroma type of mesenchymal tissue or a primitive type of mesenchyme, but that little can be said about the structure of the ground substance since neither the PAS nor the muci- FIG. 4 Remnants of dental lamina from a normally developing tooth germ. Stain H. and E. Orig. mag. 60. carmine stains were positive. One would be inclined to lean toward the view that the lesion consists primarily of a primitive mesenchymal tissue because there is a large reticular network present and only slight collagen formation has occurred. The odontogenic epithelium in this particular lesion bears some resemblance to the remnants of the dental lamina and does not appear to be taking a very active part in the formation of the tumour (Fig. 4). There seems little doubt that it is an intraosseous benign neoplasm. No mitoses were seen in this tissue, which would agree with its very benign nature. Because of the anatomical situation of the lesion, one wonders whether this odontogenic epithelium is not a remnant of the dental lamina and the lesion is an odontogenic fibroma or an odontogenic myxoma and not a 'mixed' tumour. The odontogenic myxoma can be ruled out if one follows Willis (196o), that there must be histological evidence of mucin. Whether this is an odontogenic fibroma or an ameloblastic fibroma would appear to depend on the criteria one uses for describing the odontogenic epithelium found in the specimen as well as the connective tissue matrix. Bhaskar (I965) points out that in the odontogenic

AMELOBLASTIC FIBROMAmCASE REPORT 15 fibroma strands or islands of odontogenic epithelium 'closely resemble those seen in the dental lamina', a view with which Blackwood (1965) appears to concur.

5 AMELOBLASTIC FIBROMAmCASE REPORT 15 fibroma strands or islands of odontogenic epithelium 'closely resemble those seen in the dental lamina', a view with which Blackwood (1965) appears to concur. In this lesion there is no sign of the formation of a stellate rcticulum by the odontogenic epithelia and yet the cells are plump, basophilic and cuboidal in nature. In some sections thcy take on the appearance of columnar cells, while in the centre of the clumps the cells become oval and disorientated so that the similarity to dental lamina is sometimes tenuous and at other times rather striking. In an odontogcnic fibroma one would cxpcct to observe more evidence of active couagcn formation, while the mesenchyme in this tissue still has many of the appearances of dental pulp. This appears to be the distinction Thoma (1954) makes and to this author seems a valid one. For the time being, it would seem that this lesion should be classified as an amcloblastic fibroma. Yet the author doubts whether it is truly a 'mixed' turnout but that one ought to consider thc odontogcnic fibroma, odontogcnic myxoma and the ameloblastic fibroma as variants of the same benign process taking place in the mesenchymal tissue. SUMMARY A case of an ameloblastic fibroma is described and the histogenesis of such a lesion discussed. The possibility of it being an odontogenic fibroma is considered as well as the merits of considering such tumours as 'mixed' in nature. ACKNOWLEDGEMENTS The author is grateful to Dr. R. Glen and Dr. S. Clamen of Winnipeg for access to their clinical records; to Mrs. Y. Pan for the histochemical work, and to Mrs. B. Tiller for typing the manuscript. REFERENCES BHASKAR, S. N. (1965). Synopsis of Oral Pathology. St. Louis: C. V. Mosby Co. BLACKWOOD, I-I. J. J. (1965). Brit. dent. ft. 119, 431. CHAUDHRY, A. P., STICKEL, F. R., GORLIN, R. J. & VICKERS, R. A. (1962). Oral Surg. 15, 86. GORLIN, R. J., CHAtlDHRY, A. P. & PINDBORG, J. J. (1961). Cancer, 14, 73- THOMA, K. H. (1954). Oral Pathology, 4th ed. St. Louis: C. V. Mosby Co. WILLIS, R. A. (I96O). Pathology of Tumours, 3rd ed. London: Butterworths.

Odontomes and Odontogenic tumours

Odontomes and Odontogenic tumours Odontomes Developmental hamartoma Hamartoma: normal tissue in abnormal location Any cells to be neoplastic it must be able to replicate, which is not seen in hamartoma