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Implantation keratinizing epidermoid cysts
Implantation keratinizing epidermoid cysts A review
and
case history
R. L. Ettinger, M.D.S., and R. D. Manderson, P.D.S.R.C.S. Ed&burgh, Xcotland DEPARTMENT
OF RESTORATIVE
DENTISTRY,
UNIVERSITY
(Ed.),
OF EDINBURGH
The pathogenesis of the implantation keratinizing epidermoid cyst is reviewed and discussed. Trauma is always the precipitating factor, and a source of epithelium capable of proliferation at that period in time is required. This epithelium may be derived from the surface epithelium or from the epithelium of adjacent glands or hair follicles. Presented is a case report of this type of lesion involving the vermilion border of the lip. The case history is of interest because the development of the lesion could very clearly be shown to be related to the facial accident. The value of a soft-tissue profile radiograph in the detection of glass is also discussed.
T
here are two types of epidermoid cyst, the congenital and the acquired. The congenital type develops at any development fusion point in the body where ectodermal tissue has become included at the line of fusion of embryonic body processes1 The acquired, posttraumatic, or implantation keratinizing epidermoid cyst is believed by most authorities to result from some previous trauma at the site. It is usually produced by a blunt instrument or object which may have driven epithelial cells into the dermis. When healing takes place the epithelial cells may behave like a cutaneous graft, multiplying and producing a central mass of keratin and growing slowly by expansion.2* 3 Posttraumatic cysts are found beneath the epithelium of the skin, just below the site of the scar. Clinically, their presence is suggested by slow-growing, painless, and well-circumscribed firm swellings, which are palpable beneath a normal cpithclial surface. REVIEW
OF THE LITERATURE
The most commonly accepted explanation of the pathogenesis of the implantation keratinizing epidermoid cyst is the “epithelium implant theory.“4, 5 This theory suggests that such a cyst originates as an implant of epithelium in deeper structures and becomes independent of the parent structures but still continues in its normal keratin-forming function. The mode of implant is suggested to be either surgical or accidental trauma. 225
Oral Surg. August, 1973
It has been suggested by King” and by Wein and Care’ that these cysts are not always due to implantation of skin but that they may develop from cells separated from the deeper layer of the epithelium or from some other source (for example, adjacent glands, hair follicles, or embryonic cell rests). Trauma is said to always precipitate the formation of these cysts. They were first called im~plantntio?~cysts by Sutton,” in 1895; King,” however, prefers the term posttrnumcrtic cyst. These cysts have been produced experimentally in animals. As early as 1884, Kauffman9 produced cysts using cocks’ combs, which contain neither hair follicles nor sweat glands; in the same year, SchwenigeP buried pieces of skin in the subcutaneous tissue of dogs in order to produee implantation cysts. These cysts were believed to bc derived from the buried surface epithelial cells. In 1905, Pcls-Jleusdenll found that magnesium disks buried in the dermis of rabbits became surrounded by epithelium. He postulated that this epithelium originated from the epithelium of adjacent glands or hair follicles, since he believed that his surgical technique did not carry surface epithelial cells to the site of the implanted disks. Manderson,12 working with titanium spiral implants in pigs, has suggested that the source of epithelium at the apex of one of the implant specimens may have been derived from the reduced enamel epithelium of an adjacent unerupted tooth. Thus, it is suggest.edthat trauma may stimulate epithelium from adjacent sites to proliferate and be the potential source of epithelium for posttraumatic cyst formation. Baker and Mitchell” successfully produced cysts in rats by the implantation of autogenous epithelium and showed that cyst growth occurred if the epithelium had a good supply of nutrient. Similar observations of cyst formation have been made in human beings, by the inclusion of epithelium in surgical wound sites. StrahanX3 observed the formation of cysts in nine of 413 hernial repairs in which whole-skin grafts were used. Gregory and Shafer I4 described four cases of ciliated cysts of the maxilla and suggested that this epithelium was derived from the antral lining entrapped at the site of incision after Caldwell-Luc Operations which had been carried out 10 to 40 years previously. Kpstcin an(l Kligman’” suggest that any trauma, blunt or penetrating, recognized or not, which is sufficient to start epithelial proliferation can result in traumatic cyst formation. The rarity of these cysts, despite almost constant trauma to hands, attests to the fact that the proper combination of events, namely, (1) trauma, (‘2) an epithelial system capable of proliferation at that moment, and (3) minimal inflammation, is exceedingly uncommon. In the head and neck it may be difficult to differentiate clinically the epidermoid cyst from implanted foreign bodies, chronic infections of the floor of the mouth, and benign and malignant, lesions of the connective tissues and the salivary glands.3l lG-lS Clinically, the congenital epidermoid cyst resemblesthe dermoid and teratoid cysts and can be differentiated from them only by histologic examination. These congenital epidermoid cysts are distinguished from the dermoid ones by the
Volume 36 Number 2
Fig. 2. Implantation
Implantation
keratinizing
keratinizing
epidermoid
cysts
227
epidermoid cyzt of the vermilion border of the lip.
Pig. 1. Histologic section of the cyst. (Hematixylin and eosin. Original magnification, x4.) E, Oral epithelium. CL!‘, Connective tissue. CL, Cyst lining. X, Xeratin in lumen of cyst.
absence of skin appendages, and from the teratoid ones which have skin and mesodermal derivatives.16t lpp2o Th e implantation keratinizing epidermoid cyst has no histologic similarity to the other lesions considered in the differential diagnosis. The observation haa been made that malignant change in the linings of odontogenic cysts appears to be more common in those that contain keratinizing epithelium.21-24However, there do not seemto be any reported casesof malignant change in implantation keratinizing epidermoid cysts. CASE REPORT A 5%year-old man was first seen on Feb. 17, 1971, for the repair of a 7-year-old mandibular denture, which was fractured in the midline. The patient was in good health, and
228
Ettinger
and Manderson
Oral August,
Burg. 1973
his past medical history was found to be uneventful. Eleven years previously, however, he had been involved in a road traffic accident, in the course of which the windshield of his car had been smashed by the impact of his forehead against it. As a consequence, he sustained multiple lacerations of the face. Shortly after the accident he noticed a hard lump in the upper lip and thought that it was a piece of glass from the windshield. Clitical examination revealed no signs of pathosis of the oral mucosa and no lymphadenopathy. However, a lesion was present on the lip, to the left of the midline on the vermilion border. The lesion was cream colored, oval in shape, and measured approximately 4 by 3 mm. On palpation, it was found to be elevated, firm, and mobile (Fig. 1). Xadiographia exanmination. A panoramic [Panorex] radiograph revealed no psthosis of the jaws. A soft-tissue profile radiograph of the lip showed no evidence of radiopacity suggestive of glass or any other radiopaque foreign bodies. A preliminary diagnosis of an encapsulated radiomcent foreign body or implantation cyst was made. Treatment was as follows: On Feb. 23, 1971, with the use of local anesthesia, an elliptical incision was made parallel to the mucocutaneous border of the lip, and the lesion was enucleated intact. The wound was closed with a single bla.ck silk suture, and the excised tissue was subjected to histopathologic examination. Healing was uneventful.
Histopathologic
report
Macroscofioally, the nodule consisted of cream-colored soft tissue, 4 by 3 mm., with smooth gray epithelium on one side. The bisected cut surface showed soft cheeselike material surrounded by a thin layer of gray tissue. Mioroscq~icdly, the sections showed an intact cyst (Fig. Z), the lumen of which was packed with keratin and lined with a thin, even layer of keratinizing, stratified squamous epithelium. The epithelium was surrounded by a little loose collagenous connective tissue. A strip of slightly atrophic keratinized lip mucosa was present aIong one edge (Fig. 3). Diccgno&: The appearances were those of an implantation keratinizing epidermoid cyst of the lip. There was no evidence of malignancy.
DISCUSSION
The history given by the pa.tient suggested the presence of a foreign body in the lip, which he believed to be glass. In the differential diagnosis of such lesions the soft-tissue profile radiograph is of value. The use of such radiographs for the diagnosis of glass fragments in soft tissues has been described by LewW and by Felman and Fisher.26, 27 They have shown as invalid the widely held concept that glass must contain lead or other heavy metals to be seen radiographic&y. In fact, all types of eommereial glass possessphysical characteristics which are different from those of ‘the surrounding soft, tissues, namely, a higher density and an effective atomic number. With a suitably exposed soft-tissue profile radiograph, it was possible in this case to eliminate the 1)ossibility of the presence of glass in the lip. Although posttraumatic cysts are usually symptomless and may not be associated in the patient’s mind with any specific injury, such injury possibly having occurred many years earlier, in the present case there was a clear and direct relationship between the facial injury and the lesion. Clinically, implantation keratinizing cysts are limited in size. Since the lumen of these cysts is packed with insoluble keratin, which does not lyse, the postulate is that they usually contain litt.le or no fluid of high osmolality and thus their expansion is limited. In the present case, the firmness and size of the lesion (4 by 3 mm.) after a period of 1Ol/, years are in keeping with the histologic findings of a cyst packed with keratin.
Volume 36 Number 2
Implantation
keratinizing
epidermoid cysts
229
Fig. J. Histologic section of the cyst. (Hematoxylin and eosin. Original magnification, x40.) E, Stratified squamous epithelium of lip. CT! Loose collagenous connective tissue. CL, Cyst lining of keratinizing stratified squamous eprthelium. K, Lumen of cyst packed with keratin.
The possible sources of epithelium in the formation of epidermoid cysts been considered. The site of the lesion described, namely, the have already vermilion border of the lip, which contains no hair follicles or sweat glands, leaves as the most probable source of epithelium in this case. the surface epithelium Thus, the most plausible explanation for the formation of this implantation epidermoid cyst is the epithelicrl implnnt theory. SUMMARY The pathogenesis of the implantation keratinizing epidermoid cyst is reviewed and discussed. Trauma is always the precipitating factor, and a source of epithelium capable of proliferation at the time of trauma is required. This epithelium may be derived from the surface epithelium or from the epithelium of adjacent glands or hair follicles. Reported is a case of this type of lesion involving the vermilion border of t,he lip. The case history is of interest because it was possible to relate very clearly the development of the lesion to the facial accident. The value of a soft-tissue profile radiograph in the detection of glass is also discussed. REFERENCES
1. Walter, J. B., and Israel, Ltd., p. 590.
M. 8.:
General
Pathology,
ed. 3, London,
1970,
J. & A. Churchill,
230
Ettinger
and Manderson
Oral August,
Burg. 19’73
2. Baker, B. R., and Mitchell, D. F.: The Pathogenesis of Epidermoid Implantation Cysts, ORAL BURG. 19: 494-501, 1965. 3. Torres, J. S., and Higa, T. T.: Epidermoidal Cysts in the Oral Cavity, ORAL Sun&. 30: 592-600, 1970. 4. Colby, R. A., and others: Colour Atlas of Oral Pathology, ed. 2, Philadelphia, 1961, J. B. Lippihcott Company, p. 21. 5. Baker, B. R.: Pathogenesis of Autogenous Skin Implantation Cysts, Alumni Bulletin, Indiana Univ. School of Dentistry, Fall, 1963, p. 19 (Abstr.). 6. King, E. S. J.: Post-traumatic Epidermoid Cysts of Hands and Fingers, Br. J. Burg. 21: 29-43, 1933. 7. Wein. M. 5.. and Caro, M. R.: Traumatic Eoithelial Cysts of the Skin, J. A. M. A. 102: L 197-260, 1934. Sutton, J. B.: A Clinical Lecture on Some Unusual Tumours, Br. Med. J. 1: 461-464, 1895. i: Kauffman, E.: tiber Enkatarrhaphie von Epithel: Ein experimenteller Beitrag zur Entetehune der Geschnulste. Virchows Arch. Pathol. Anat. 97: 236-253. 1884. 10. Schweniger, E. : Beitrag zur experimentellen Erzuegung von ‘Hautgeschwulsten (Atheromen) durch subcutan Verlagerte mit Mutterbochen in Verbindung gelassene Hautstiicke, Charite-Ann. 11: 642-649, 1884; Berlin, 1886. 11. Pels-Leusden, F. : tfber abnorme Epithelisierung und traumatische Epithelcysten, D&h. Med. Wochnschr. 31: 1340-1342, 1905. 1‘2. Manderson, R. D.: Experimental Intra-osseous Implantation in the Jaws of Pigs, Dent. Pratt. Dent. Rec. 22: 225-231, 1972. 13. Strahan, A. W. B.: Hernial Repair by Whole Skin Graft With Report on 413 Cases, Br. J. Surg. 38: 276-284, 1951. 14. Gregory, G. T., and Shafer, W. C.: Surgical Ciliated Cysts of the Maxilla. Report of Cases, J. Oral Surg. 16: 251-253, 1958. 15. Epstein, W. L., and Kligman, A. M.: Epithelial Cysts in Buried Human Skin, Arch. Dermatol. 76: 437-445, 1957. 16. Johnston, W. H.: Cysts of the Floor of the Mouth, Ann. Otol. Rhinol. L’aryngol. 51: 917930. 1942. 17. Keiln, E. E.: Oral Epidermal Cysts and Probable Histogenesis. Report of a Case, ORAL SURO. 19: 359-364, 1965. 18. Portales, C., and L’osealzo, L. J.: Unusual Epidermal Cyst, ORAL SURG. 24: 581-584, 1967. 19. Erich, J. B.: Sebaceous, Mucous, Dermoid and Epidermoid Cysts, Am. J. Surg. 50: 672677, 1940. 20. Meyer, I.: Dermoid Cysts (Dermoids) of the Floor of the Mouth, ORAL SURG. 8: 11491164, 195.5.
21. Kramer, I. R. H.: Ameloblastoma: A Clinicopathological Appraisal, Br. J. Oral Burg. 1: 13-28, 1963. 22. To&r, P. A.: Origin and Growth of Cysts of the Jaws, Ann. R. Coll. Surg. Engl. 40: 306-336, 1967. 23. Browne, R. M.: The odontogenic Keratocyst. Histological Features and Their Correlation With Clinical Behaviour, Br. Dent. J. 131: 249-259, 1971. 24. Payne, T. F.: An Analysis of the Clinical and Histopathologic Parameters of the Odontogenic Keratocyst, ORAL SURG. 33: 538-546, 1972. 25. Lewis, R. W.: A Roentgenographic Study of Glass and Its Visibility As a Foreign Body, Am. J. Roentgenol. Radium Ther. Nucl. Med. 27: 853-857, 1932. 26. Felman, A. H., and Fisher, M. S.: Radiographic Detection of Glass in Soft Tissue, Radiology 92: 1529-1531, 1969. 27. Felman, A. H., and Fisher, M. S.: Detection of Glass in Soft Tissue by X-Ray, Pediatrics 45: 478-480, 1970. Reprint requests to : Dr. R. L. Ettinger Department of Removable Prosthodonties University of Iowa Iowa City, Iowa 52242 or Dr. R. D. Manderson Department of Dental Prosthetics University College Hospital Dental School Mortimer Market London, W.C. I, England
and
case history
R. L. Ettinger, M.D.S., and R. D. Manderson, P.D.S.R.C.S. Ed&burgh, Xcotland DEPARTMENT
OF RESTORATIVE
DENTISTRY,
UNIVERSITY
(Ed.),
OF EDINBURGH
The pathogenesis of the implantation keratinizing epidermoid cyst is reviewed and discussed. Trauma is always the precipitating factor, and a source of epithelium capable of proliferation at that period in time is required. This epithelium may be derived from the surface epithelium or from the epithelium of adjacent glands or hair follicles. Presented is a case report of this type of lesion involving the vermilion border of the lip. The case history is of interest because the development of the lesion could very clearly be shown to be related to the facial accident. The value of a soft-tissue profile radiograph in the detection of glass is also discussed.
T
here are two types of epidermoid cyst, the congenital and the acquired. The congenital type develops at any development fusion point in the body where ectodermal tissue has become included at the line of fusion of embryonic body processes1 The acquired, posttraumatic, or implantation keratinizing epidermoid cyst is believed by most authorities to result from some previous trauma at the site. It is usually produced by a blunt instrument or object which may have driven epithelial cells into the dermis. When healing takes place the epithelial cells may behave like a cutaneous graft, multiplying and producing a central mass of keratin and growing slowly by expansion.2* 3 Posttraumatic cysts are found beneath the epithelium of the skin, just below the site of the scar. Clinically, their presence is suggested by slow-growing, painless, and well-circumscribed firm swellings, which are palpable beneath a normal cpithclial surface. REVIEW
OF THE LITERATURE
The most commonly accepted explanation of the pathogenesis of the implantation keratinizing epidermoid cyst is the “epithelium implant theory.“4, 5 This theory suggests that such a cyst originates as an implant of epithelium in deeper structures and becomes independent of the parent structures but still continues in its normal keratin-forming function. The mode of implant is suggested to be either surgical or accidental trauma. 225
Oral Surg. August, 1973
It has been suggested by King” and by Wein and Care’ that these cysts are not always due to implantation of skin but that they may develop from cells separated from the deeper layer of the epithelium or from some other source (for example, adjacent glands, hair follicles, or embryonic cell rests). Trauma is said to always precipitate the formation of these cysts. They were first called im~plantntio?~cysts by Sutton,” in 1895; King,” however, prefers the term posttrnumcrtic cyst. These cysts have been produced experimentally in animals. As early as 1884, Kauffman9 produced cysts using cocks’ combs, which contain neither hair follicles nor sweat glands; in the same year, SchwenigeP buried pieces of skin in the subcutaneous tissue of dogs in order to produee implantation cysts. These cysts were believed to bc derived from the buried surface epithelial cells. In 1905, Pcls-Jleusdenll found that magnesium disks buried in the dermis of rabbits became surrounded by epithelium. He postulated that this epithelium originated from the epithelium of adjacent glands or hair follicles, since he believed that his surgical technique did not carry surface epithelial cells to the site of the implanted disks. Manderson,12 working with titanium spiral implants in pigs, has suggested that the source of epithelium at the apex of one of the implant specimens may have been derived from the reduced enamel epithelium of an adjacent unerupted tooth. Thus, it is suggest.edthat trauma may stimulate epithelium from adjacent sites to proliferate and be the potential source of epithelium for posttraumatic cyst formation. Baker and Mitchell” successfully produced cysts in rats by the implantation of autogenous epithelium and showed that cyst growth occurred if the epithelium had a good supply of nutrient. Similar observations of cyst formation have been made in human beings, by the inclusion of epithelium in surgical wound sites. StrahanX3 observed the formation of cysts in nine of 413 hernial repairs in which whole-skin grafts were used. Gregory and Shafer I4 described four cases of ciliated cysts of the maxilla and suggested that this epithelium was derived from the antral lining entrapped at the site of incision after Caldwell-Luc Operations which had been carried out 10 to 40 years previously. Kpstcin an(l Kligman’” suggest that any trauma, blunt or penetrating, recognized or not, which is sufficient to start epithelial proliferation can result in traumatic cyst formation. The rarity of these cysts, despite almost constant trauma to hands, attests to the fact that the proper combination of events, namely, (1) trauma, (‘2) an epithelial system capable of proliferation at that moment, and (3) minimal inflammation, is exceedingly uncommon. In the head and neck it may be difficult to differentiate clinically the epidermoid cyst from implanted foreign bodies, chronic infections of the floor of the mouth, and benign and malignant, lesions of the connective tissues and the salivary glands.3l lG-lS Clinically, the congenital epidermoid cyst resemblesthe dermoid and teratoid cysts and can be differentiated from them only by histologic examination. These congenital epidermoid cysts are distinguished from the dermoid ones by the
Volume 36 Number 2
Fig. 2. Implantation
Implantation
keratinizing
keratinizing
epidermoid
cysts
227
epidermoid cyzt of the vermilion border of the lip.
Pig. 1. Histologic section of the cyst. (Hematixylin and eosin. Original magnification, x4.) E, Oral epithelium. CL!‘, Connective tissue. CL, Cyst lining. X, Xeratin in lumen of cyst.
absence of skin appendages, and from the teratoid ones which have skin and mesodermal derivatives.16t lpp2o Th e implantation keratinizing epidermoid cyst has no histologic similarity to the other lesions considered in the differential diagnosis. The observation haa been made that malignant change in the linings of odontogenic cysts appears to be more common in those that contain keratinizing epithelium.21-24However, there do not seemto be any reported casesof malignant change in implantation keratinizing epidermoid cysts. CASE REPORT A 5%year-old man was first seen on Feb. 17, 1971, for the repair of a 7-year-old mandibular denture, which was fractured in the midline. The patient was in good health, and
228
Ettinger
and Manderson
Oral August,
Burg. 1973
his past medical history was found to be uneventful. Eleven years previously, however, he had been involved in a road traffic accident, in the course of which the windshield of his car had been smashed by the impact of his forehead against it. As a consequence, he sustained multiple lacerations of the face. Shortly after the accident he noticed a hard lump in the upper lip and thought that it was a piece of glass from the windshield. Clitical examination revealed no signs of pathosis of the oral mucosa and no lymphadenopathy. However, a lesion was present on the lip, to the left of the midline on the vermilion border. The lesion was cream colored, oval in shape, and measured approximately 4 by 3 mm. On palpation, it was found to be elevated, firm, and mobile (Fig. 1). Xadiographia exanmination. A panoramic [Panorex] radiograph revealed no psthosis of the jaws. A soft-tissue profile radiograph of the lip showed no evidence of radiopacity suggestive of glass or any other radiopaque foreign bodies. A preliminary diagnosis of an encapsulated radiomcent foreign body or implantation cyst was made. Treatment was as follows: On Feb. 23, 1971, with the use of local anesthesia, an elliptical incision was made parallel to the mucocutaneous border of the lip, and the lesion was enucleated intact. The wound was closed with a single bla.ck silk suture, and the excised tissue was subjected to histopathologic examination. Healing was uneventful.
Histopathologic
report
Macroscofioally, the nodule consisted of cream-colored soft tissue, 4 by 3 mm., with smooth gray epithelium on one side. The bisected cut surface showed soft cheeselike material surrounded by a thin layer of gray tissue. Mioroscq~icdly, the sections showed an intact cyst (Fig. Z), the lumen of which was packed with keratin and lined with a thin, even layer of keratinizing, stratified squamous epithelium. The epithelium was surrounded by a little loose collagenous connective tissue. A strip of slightly atrophic keratinized lip mucosa was present aIong one edge (Fig. 3). Diccgno&: The appearances were those of an implantation keratinizing epidermoid cyst of the lip. There was no evidence of malignancy.
DISCUSSION
The history given by the pa.tient suggested the presence of a foreign body in the lip, which he believed to be glass. In the differential diagnosis of such lesions the soft-tissue profile radiograph is of value. The use of such radiographs for the diagnosis of glass fragments in soft tissues has been described by LewW and by Felman and Fisher.26, 27 They have shown as invalid the widely held concept that glass must contain lead or other heavy metals to be seen radiographic&y. In fact, all types of eommereial glass possessphysical characteristics which are different from those of ‘the surrounding soft, tissues, namely, a higher density and an effective atomic number. With a suitably exposed soft-tissue profile radiograph, it was possible in this case to eliminate the 1)ossibility of the presence of glass in the lip. Although posttraumatic cysts are usually symptomless and may not be associated in the patient’s mind with any specific injury, such injury possibly having occurred many years earlier, in the present case there was a clear and direct relationship between the facial injury and the lesion. Clinically, implantation keratinizing cysts are limited in size. Since the lumen of these cysts is packed with insoluble keratin, which does not lyse, the postulate is that they usually contain litt.le or no fluid of high osmolality and thus their expansion is limited. In the present case, the firmness and size of the lesion (4 by 3 mm.) after a period of 1Ol/, years are in keeping with the histologic findings of a cyst packed with keratin.
Volume 36 Number 2
Implantation
keratinizing
epidermoid cysts
229
Fig. J. Histologic section of the cyst. (Hematoxylin and eosin. Original magnification, x40.) E, Stratified squamous epithelium of lip. CT! Loose collagenous connective tissue. CL, Cyst lining of keratinizing stratified squamous eprthelium. K, Lumen of cyst packed with keratin.
The possible sources of epithelium in the formation of epidermoid cysts been considered. The site of the lesion described, namely, the have already vermilion border of the lip, which contains no hair follicles or sweat glands, leaves as the most probable source of epithelium in this case. the surface epithelium Thus, the most plausible explanation for the formation of this implantation epidermoid cyst is the epithelicrl implnnt theory. SUMMARY The pathogenesis of the implantation keratinizing epidermoid cyst is reviewed and discussed. Trauma is always the precipitating factor, and a source of epithelium capable of proliferation at the time of trauma is required. This epithelium may be derived from the surface epithelium or from the epithelium of adjacent glands or hair follicles. Reported is a case of this type of lesion involving the vermilion border of t,he lip. The case history is of interest because it was possible to relate very clearly the development of the lesion to the facial accident. The value of a soft-tissue profile radiograph in the detection of glass is also discussed. REFERENCES
1. Walter, J. B., and Israel, Ltd., p. 590.
M. 8.:
General
Pathology,
ed. 3, London,
1970,
J. & A. Churchill,
230
Ettinger
and Manderson
Oral August,
Burg. 19’73
2. Baker, B. R., and Mitchell, D. F.: The Pathogenesis of Epidermoid Implantation Cysts, ORAL BURG. 19: 494-501, 1965. 3. Torres, J. S., and Higa, T. T.: Epidermoidal Cysts in the Oral Cavity, ORAL Sun&. 30: 592-600, 1970. 4. Colby, R. A., and others: Colour Atlas of Oral Pathology, ed. 2, Philadelphia, 1961, J. B. Lippihcott Company, p. 21. 5. Baker, B. R.: Pathogenesis of Autogenous Skin Implantation Cysts, Alumni Bulletin, Indiana Univ. School of Dentistry, Fall, 1963, p. 19 (Abstr.). 6. King, E. S. J.: Post-traumatic Epidermoid Cysts of Hands and Fingers, Br. J. Burg. 21: 29-43, 1933. 7. Wein. M. 5.. and Caro, M. R.: Traumatic Eoithelial Cysts of the Skin, J. A. M. A. 102: L 197-260, 1934. Sutton, J. B.: A Clinical Lecture on Some Unusual Tumours, Br. Med. J. 1: 461-464, 1895. i: Kauffman, E.: tiber Enkatarrhaphie von Epithel: Ein experimenteller Beitrag zur Entetehune der Geschnulste. Virchows Arch. Pathol. Anat. 97: 236-253. 1884. 10. Schweniger, E. : Beitrag zur experimentellen Erzuegung von ‘Hautgeschwulsten (Atheromen) durch subcutan Verlagerte mit Mutterbochen in Verbindung gelassene Hautstiicke, Charite-Ann. 11: 642-649, 1884; Berlin, 1886. 11. Pels-Leusden, F. : tfber abnorme Epithelisierung und traumatische Epithelcysten, D&h. Med. Wochnschr. 31: 1340-1342, 1905. 1‘2. Manderson, R. D.: Experimental Intra-osseous Implantation in the Jaws of Pigs, Dent. Pratt. Dent. Rec. 22: 225-231, 1972. 13. Strahan, A. W. B.: Hernial Repair by Whole Skin Graft With Report on 413 Cases, Br. J. Surg. 38: 276-284, 1951. 14. Gregory, G. T., and Shafer, W. C.: Surgical Ciliated Cysts of the Maxilla. Report of Cases, J. Oral Surg. 16: 251-253, 1958. 15. Epstein, W. L., and Kligman, A. M.: Epithelial Cysts in Buried Human Skin, Arch. Dermatol. 76: 437-445, 1957. 16. Johnston, W. H.: Cysts of the Floor of the Mouth, Ann. Otol. Rhinol. L’aryngol. 51: 917930. 1942. 17. Keiln, E. E.: Oral Epidermal Cysts and Probable Histogenesis. Report of a Case, ORAL SURO. 19: 359-364, 1965. 18. Portales, C., and L’osealzo, L. J.: Unusual Epidermal Cyst, ORAL SURG. 24: 581-584, 1967. 19. Erich, J. B.: Sebaceous, Mucous, Dermoid and Epidermoid Cysts, Am. J. Surg. 50: 672677, 1940. 20. Meyer, I.: Dermoid Cysts (Dermoids) of the Floor of the Mouth, ORAL SURG. 8: 11491164, 195.5.
21. Kramer, I. R. H.: Ameloblastoma: A Clinicopathological Appraisal, Br. J. Oral Burg. 1: 13-28, 1963. 22. To&r, P. A.: Origin and Growth of Cysts of the Jaws, Ann. R. Coll. Surg. Engl. 40: 306-336, 1967. 23. Browne, R. M.: The odontogenic Keratocyst. Histological Features and Their Correlation With Clinical Behaviour, Br. Dent. J. 131: 249-259, 1971. 24. Payne, T. F.: An Analysis of the Clinical and Histopathologic Parameters of the Odontogenic Keratocyst, ORAL SURG. 33: 538-546, 1972. 25. Lewis, R. W.: A Roentgenographic Study of Glass and Its Visibility As a Foreign Body, Am. J. Roentgenol. Radium Ther. Nucl. Med. 27: 853-857, 1932. 26. Felman, A. H., and Fisher, M. S.: Radiographic Detection of Glass in Soft Tissue, Radiology 92: 1529-1531, 1969. 27. Felman, A. H., and Fisher, M. S.: Detection of Glass in Soft Tissue by X-Ray, Pediatrics 45: 478-480, 1970. Reprint requests to : Dr. R. L. Ettinger Department of Removable Prosthodonties University of Iowa Iowa City, Iowa 52242 or Dr. R. D. Manderson Department of Dental Prosthetics University College Hospital Dental School Mortimer Market London, W.C. I, England