J Oral Maxillofac Surg 49:268=271,1991
Nasopalatine An Analysis
Duct Cyst: of 334 Cases
KIMBERLY S. SWANSON, DDS,* GEORGE E. KAUGARS, DDS,t AND JOHN C. GUNSOLLEY, DDS, MS* The nasopalatine duct cyst (NPDC) is the most common cyst of nonodontogenic origin in the maxilla. However, the information reported about this lesion consists primarily of small surveys and isolated case reports. The purpose of this retrospective investigation was to gather demographic, clinical, and histologic data on a large series of NPDCs, and to compare the findings with those of previous studies. In this study, the overall mean age at diagnosis was 42.5 years, and there was a slight male predilection. The mean radiographic diameter was 17.1 mm, but 75% of the lesions were 20 mm or less in diameter. Symptoms were present in at least 70% of the cases. Only 28% of the specimens contained respiratory epithelium. There was no correlation between radiographic size, patient’s age, presenting symptoms, or type of epithelium. Recurrence was noted in only 2% of the cases.
of 334 NPDCs and compare the present with those of previous studies.
Meyer first described the nasopalatine duct cyst (NPDC) in 1914as a “supernumerary nasal sinus.“’ The NPDC, also popularly known as the incisive canal cyst, is the most common nonodontogenic cyst in the maxilla, occurring in 1% of the population. 2-8It is thought to originate from epithelial remnants of the nasopalatine duct,2,3,9,‘0 which might be stimulated to proliferate by trauma, infection,” or mucous retention.4.5’9 Spontaneous cystic degeneration of epithelial remnants has also been suggested as a cause because these cysts have been found in human fetal incisive canals.‘* Much of the information concerning NPDCs consists of isolated case reports and small surveys. There has been no large study of this relatively common cyst to date. The purpose of this retrospective investigation is to present data on a series
Materials and Methods
Of the lesions submitted to the Oral Pathology Diagnostic Service from January 1, 1970, to September 20, 1989, all those diagnosed as incisive canal cyst, nasopalatine duct cyst, median palatine cysts, or cysts of the incisive papilla were reviewed microscopically by the authors. Data regarding age, race, and sex of the patient, symptoms, radiographic size, recurrence, and type of practitioner submitting the specimen were obtained from the biopsy request forms. Criteria for inclusion in the study were the histologic presence of cystic epithelium and the presence of an intraosseous radiolucency in the maxillary midline as stated by the practitioner on the biopsy form. Lesions with radiographic evidence of calcification and those associated with nonvital teeth suspected of being endodontic in origin were excluded. Radiographic diameter in millimeters was recorded as provided on the biopsy form or as measured from enclosed radiographs. Recurrence was identified by the history given on the biopsy form by the practitioner.
Received from the Medical College of Virginia, Richmond. * Chief Resident, Department of Oral and Maxillofacial Surgery. t Associate Professor, Department of Oral Pathology. $ Assistant Professor, Departments of Periodontics and Biostatistics. Address correspondence and reprint requests to Dr Kaugars: Department of Oral Pathology, Medical College of Virginia, Box 566, MCV Station, Richmond, VA 23298. 0 1991 American Association geons 0278-2391/91/4903-0009/$3.00/O
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Table 2. Radlognphic Diameter of Nasopalatine Duct Cysts (N = 116)
Results Of the 69,988 biopsies accessioned during the period of the study, 334 acceptable cases (0.5%) were identified. Demographic information is presented in Table 1. The overall mean age was 42.5 years, with a range from 9 to 84 years. There was no significant age difference at time of diagnosis between males and females, or blacks and whites. A slight majority, 54%, occurred in males. However, this can be considered a significant sex predilection because only 44.3% of all the submitted biopsies were from males (P = .OOOl). Most patients (93.0%) were white and only 6.0% were black, although 15.3% of all biopsies submitted were from black patients (P = .0065). The mean radiographic diameter was 17.1 mm in 116 cases with which this information was available (Table 2). A small number (6.4%) of cysts were 6 mm or less in diameter, which is within the normal anatomical size range for the incisive cana1.9Y10~‘2 Only one of the eight cysts 6 mm or less in diameter was asymptomatic. There was no correlation between radiographic size of the NPDC and age of the patient. Mean radiographic diameter in whites was smaller than in blacks (P = .0019). Males had a larger mean radiographic diameter than females (P = .0233). The sample size was too small to assess size variations when both race and gender were considered together. Clinical symptoms were common; 52% of patients complained of swelling, 25% had drainage, 20% experienced pain, and 70% of all cases had a combination of these symptoms. Bony expansion was noted in only 1.4% of patients. Palatal numbness, altered or salty taste, or tooth movement was noted in three cases or less in each instance. Up to 29% of patients may have been asymptomatic; howTable 1. Patients Diagnosed With Nasopalatine Duct Cysts (N = 334) Age, mean (yr) Overall Male Female White Black Sex Male Female Race White Black Oriental Not stated * Numbers within parentheses cases.
42.5 43.3 41.5 42.6 38.4 54.2% (181) 45.8% (153) 93.0% (291) 6.0% (20) 1.O% (2) (21) represent the actual number of
Size. mean (mm) Overall Male Female White Black Size, mean (mm) ~6 ( 6.4%) 7-10 (18.6%) 11-15 (25.0%) 16-20 (25.0%) 21-30 (15.0%) 31-50 ( 7.5%) 51-60 ( 2.5%)
17.1 18.9 14.2 16.4 27.8
ever, the information regarding symptoms was not included on the biopsy request form by the practitioner. Symptoms or lack of symptoms was not significantly related to patient age or gender. The presence of symptoms also was not related to radiographic diameter. Histologically, only respiratory epithelium was seen in 9.8% of cases. Respiratory epithelium in combination with one or more other types of epithelium was seen in 18.2%, and 71.8% of lesions had either squamous, columnar, cuboidal, or some combination of these epithelial types but no respiratory epithelium. The type of epithelium present was not related to cyst size. Most biopsy specimens (96.6%) were submitted by oral and maxillofacial surgeons. The remainder were submitted by periodontists, endodontists, and general practitioners. There was no significant difference in lesions removed by surgeons as compared with those removed by other dental practitioners, with one exception: all 10 lesions removed by nonoral and maxillofacial surgeons were asymptomatic . Recurrence was noted in 2% of the cases. No difference was found when comparing cysts that recurred to those that did not. The time between initial treatment and recurrence ranged from 3 months to 6 years. Discussion
Our series of 334 NPDCs comes from a selected sample because all were surgically removed. It is probable that some NPDCs are recognized but are not treated. Because only 57% of the US adult population seeks regular dental care, it is likely that some NPDCs remain undiagnosed.13 Therefore, it is possible that the NPDCs that were surgically removed were not representative of all NPDCs. The NPDC is considered by some to be develop-
270
NASOPALATINEDUCTCYST
The trigger for the prolifermental in origin. 2*3V9*15 ation of epithelial remnants and subsequent cyst formation is unknown. Trauma, bacterial infection, and mucous retention have been suggested and subsequently rejected as mechanisms of cystic pathogenesis. 4,5,7,8,11,12,i6*i7 that a genetic factor may be involved because they found large, rapidly growing NPDCs in young black patients. Spontaneous cystic degeneration of the contents of the incisive canal has been postulated to explain the observation of NPDCs in all ages, including the human fetus.12 The spontaneous cystic degeneration theory seems the most plausible in view of our findings. We found no relationship between patient’s age and lesion size. If the NPDCs were developmental, the size of the lesion would increase as the patient aged. Smaller lesions would be found in young people, and larger lesions would be in older patients. The classification of the NPDC as developmental must be questioned because of the lack of correlation between age and radiographic size. Roper-Hall may have been the tirst to recommend the use of radiographic size in diagnosing NPDCs when he concluded that any radiographic lesion less than 6 mm in diameter should be considered within normal limits.’ This was based partially on the finding that the diameter of the average incisive foramen was approximately 3 mm. However, radiographic magnification, especially in panoramic radiographs, should also be considered. In addition, technical factors such as the angulation of the x-ray beam can alter the apparent radiographic size of a lesion. The presence of symptoms may be an indication for surgical intervention when the radiographic diameter of the lesion is less than 6 mm. Our series had eight cysts of 6 mm or less in diameter, seven of which were asymptomatic. The presence of symptoms was probably the reason that these lesions were removed. Reports of mean radiographic diameter of NPDCs range from 6 to 15 mm. *J~*~*In the present study, the mean diameter of 17.1 mm is larger than those previously reported. The average size of cysts in males was significantly larger than that in females, and the average cyst size in blacks was larger than in whites. One might speculate that larger cysts occur in patients with larger maxillas, or in patients who have a delayed onset of symptoms. Because males seek dental care less freit is plausible that males are quently than femalesI less likely to have asymptomatic NPDCs diagnosed at an early stage. In a similar fashion, blacks seek dental care less frequently than do whites,13 so it is reasonable to expect the mean radiographic size to be larger. A larger size at the time of diagnosis in males might also be related to a delay in the develNofijeeta1'8
suggested
opment of symptoms until the cyst reaches a critical size. Unfortunately, our data did not confirm or disprove any of these theories. Age was not related to size as might be expected for a developmental lesion. The rarity of NPDCs in the first decade of life was somewhat surprising in view of the increasing popularity of panoramic radiography in young patients. A limited potential for growth is demonstrated by the relatively small mean diameter (17.1 mm) and the large number of cases (75%) of cysts that were 20 mm or less in diameter. The relatively limited growth potential is also demonstrated by the finding that only 10% of the NPDCs were greater than 30 mm in diameter. These findings indicate a generalized lack of aggressive behavior and justify observation in selected cases. NPDCs are usually discovered in patients between the fourth and sixth decades of life.2*3*‘2,‘7 The mean age has been reported from 31 to 54 years.8,‘0 In a survey of 70 cysts, one of the largest previous series, Bodin et ali6 reported a mean age of 45 years. In agreement with these studies, our series showed a mean age of 42.5 years, with no significant difference between ages of males or females, and blacks or whites at time of diagnosis. Most of the available literature reports a male predilection for the NPDC. Annaroth et al8 reported a male:female ratio of I .7 to 1 in 35 cases. In a series of 51 cysts, Nortje et al” found 64.7% of the cases in males. Bodin et alI6 reported a similar 67% male predilection in their study of 70 lesions. Abrams et all2 are the only investigators who have reported an almost equal distribution between males and females. In the present study, 54% of the cases occurred in males. However, our biopsy service has more specimens submitted from female patients (56%). If the occurrence of NPDC has no sex predilection, then our series would be expected to show an approximate incidence in males of 44%. With this in mind, our findings suggest a slight male predilection for the NPDC. Goaz et al2 state that NPDCs occur equally in blacks and whites. The series of 70 cysts from Bodin et alI6 were all from white Swedish patients. Nortje et al” believe that blacks are more likely to develop these cysts; however, their study was conducted in a predominantly black South African population. Chamda et al6 studied 960 skulls from South African blacks and stated that the NPDC may occur more frequently in blacks. In our series of 334 NPDCs, 93.0% occurred in whites and only 6.0% in blacks. This may have occurred because whites are more likely to visit a dentist than blacks (59% vs 43%)” and, therefore, are more likely to be treated. The literature indicates that most NPDCs are
SWANSON ET AL
asymptomatic unless secondarily infected. 2.9.7-9,‘7.‘9Symptoms, if present, are so minor that they may be easily tolerated for long periods of time.‘.16 The most common presenting symptoms are swelling, drainage, and pain.8~‘2*‘6*18Tooth movement was noted by one group to occur in 78.4% of the cases.18 It has been stated that larger cysts produce more symptoms,‘6 but others maintain that size is not related to symptoms.8 The percentage of asymptomatic cysts reported ranges from 39% to 50%. ‘.I2 Only 29% were asymptomatic in the present study. It is possible that this is an overestimate because practitioners may not have completed the biopsy request form properly. Over 70% of NPDCs in our series were associated with some combination of swelling, pain, or drainage. Surprisingly, symptoms were not related to radiographic size. Some patients with large lesions had few or no symptoms, whereas some patients with small lesions had severe symptoms. Symptoms were also not related to age. Elderly patients reported the same frequency of symptoms as younger ones. Symptoms were also reported with equal frequency in males and females. It is reasonable to assume that the percentage of asymptomatic NPDCs would be higher in a study based on radiographic evaluation rather than a study of surgical specimens, which are likely to have been removed due to symptoms. Squamous epithelium has been reported in 75% to 82% of NPDCS.~.” Ciliated (respiratory) epithehum has been found in 23% to 42% of these Cysts?~‘~ More than one epithelial type is commanly found.5*” It is generally accepted that the type of epithelium is related to the vertical position within the canal of the cystic degeneration. Squamous metaplasia may account for the preponderante of squamous epithelium seen. In agreement with previous studies, our series showed that 71.8% ofNPDCs have either squamous, columnar, or cuboidal epithelium; 9.8% show respiratory epithelium alone; and 18.2% have both respiratory and squamous type epithelium. Therefore, respiratory epithelium was seen in 28.0% of the lesions. The type of epithelium was not related to cyst size. As expected, 96.6% of the 334 NPDCs were submitted by oral and maxillofacial surgeons. No difference in size by lesions removed by surgeons and other practitioners was seen. Ah 10 NPDCs removed by nonoral surgeons were asymptomatic. This may indicate that these practitioners did not
271
record symptoms on the biopsy form or perhaps felt that removal of asymptomatic lesions was indicated. It is generally agreed that NPDCs have a low recurrence rate; reports of recurrence range from 0% to 11%.16 The results of this investigation are consistent with previous studies, showing a recurrence rate of only 2%. Because only seven cysts recurred, it was not possible to determine the characteristics that made them different from cysts that did not recur.
I. Meyer AW: A unique supernumerary paranasal sinus directly above the superior incisors. J Anat 48:118, 1914 2. Goaz PW, White SC: Oral Radiology: Principles and Interpretation. St Louis, MO, MosbyT-1982. pp 443-445 3. Shafer WG. Hine MK. Levv BM: A Textbook of Oral Pathology (ed 4). PhiladelphLa, PA, Saunders, 1983, pp 70-72 4. Stafne EC. Austin LT. Gardner BS: Median anterior maxillary cysts. J Am Dent Assoc 23:801. 1936 5. Allard RHB. Van Der Kwast WAM. Van Der Waal I: Nasopalatine duct cyst. Review of the’literature and report of 22 cases. Int J Oral Surg 10447, 1981 6. Chamda RA. Shear M: Dimensions of incisive fossae on dry skulls and radiographs. Int J Oral Surg 9:452. 1980 7. Camobell JJ. Baden E. Williams AC: Nasopalatine cyst of unusual size: Report of case. J Oral Surg-31:776, 1973 8. Anneroth Cl. Hall G, Stuge U: Nasopalatine duct cyst. Int J Oral Maxillofac Surg 15572, 1986 9. Roper-Hall HT: Cysts of developmental origin in the premaxillary region, with special reference to their diagnosis. J Br Dent Assoc 65:29, 1938 IO. Nortje CJ. Wood RE: The radiologic features of the nasopalatine duct cyst. An analysis of 46 cases. Dentomaxillofac Radio1 17:129, 1988 I I. Brode H, Araiche M: Nasopalatine cyst: Report of a case. J Oral Surg 17&l, 1959 12. Abrams AM, Howell FV, Bullock WK: Nasopalatine cysts. Oral Surg Oral Med Oral Pathol 16:306. 1963 13. National Center for Health Statistics. US Dept. of Health & Human Services: Use of Dental Services and Dental Health, United States, 1986; National Health Survey, Series IO, Number 165; DHHS Publication No. (PHS) 881593, October 1988 14. Pindborg JJ, Kramer IRH. Torloni H: Histological typing of odontogenic tumours, jaw cysts, and allied lesions. World Health Oreanization. Geneva. 1971 15. Choukas NC: Case report of a’median palatine cyst with criteria for a differential diagnosis. Oral Surg Oral Med Oral Pathol 10:237, 1957 16. Bodin I, Isacsson G, Julin P: Cysts of the nasopalatine duct. Int J Oral Maxillofac Surg l5:6%, 1986 17. Hedin M, Klanfeldt A. Persson G: Surgical treatment of nasopalatine duct cysts: A follow-up study. Int J Oral Surg 71427, 1978 18. Nortje CJ, Farman AG: Nasopalatine duct cyst. An aggressive condition in adolescent negroes from south Africa? Int J Oral Surg 7:65, 1978 19. Staretz LR, Brada BJ, Schott TR: Well-defined radiolucent lesion in the maxillary anterior region. J Am Dent Assoc 120:335, 1990
Nasopalatine An Analysis
Duct Cyst: of 334 Cases
KIMBERLY S. SWANSON, DDS,* GEORGE E. KAUGARS, DDS,t AND JOHN C. GUNSOLLEY, DDS, MS* The nasopalatine duct cyst (NPDC) is the most common cyst of nonodontogenic origin in the maxilla. However, the information reported about this lesion consists primarily of small surveys and isolated case reports. The purpose of this retrospective investigation was to gather demographic, clinical, and histologic data on a large series of NPDCs, and to compare the findings with those of previous studies. In this study, the overall mean age at diagnosis was 42.5 years, and there was a slight male predilection. The mean radiographic diameter was 17.1 mm, but 75% of the lesions were 20 mm or less in diameter. Symptoms were present in at least 70% of the cases. Only 28% of the specimens contained respiratory epithelium. There was no correlation between radiographic size, patient’s age, presenting symptoms, or type of epithelium. Recurrence was noted in only 2% of the cases.
of 334 NPDCs and compare the present with those of previous studies.
Meyer first described the nasopalatine duct cyst (NPDC) in 1914as a “supernumerary nasal sinus.“’ The NPDC, also popularly known as the incisive canal cyst, is the most common nonodontogenic cyst in the maxilla, occurring in 1% of the population. 2-8It is thought to originate from epithelial remnants of the nasopalatine duct,2,3,9,‘0 which might be stimulated to proliferate by trauma, infection,” or mucous retention.4.5’9 Spontaneous cystic degeneration of epithelial remnants has also been suggested as a cause because these cysts have been found in human fetal incisive canals.‘* Much of the information concerning NPDCs consists of isolated case reports and small surveys. There has been no large study of this relatively common cyst to date. The purpose of this retrospective investigation is to present data on a series
Materials and Methods
Of the lesions submitted to the Oral Pathology Diagnostic Service from January 1, 1970, to September 20, 1989, all those diagnosed as incisive canal cyst, nasopalatine duct cyst, median palatine cysts, or cysts of the incisive papilla were reviewed microscopically by the authors. Data regarding age, race, and sex of the patient, symptoms, radiographic size, recurrence, and type of practitioner submitting the specimen were obtained from the biopsy request forms. Criteria for inclusion in the study were the histologic presence of cystic epithelium and the presence of an intraosseous radiolucency in the maxillary midline as stated by the practitioner on the biopsy form. Lesions with radiographic evidence of calcification and those associated with nonvital teeth suspected of being endodontic in origin were excluded. Radiographic diameter in millimeters was recorded as provided on the biopsy form or as measured from enclosed radiographs. Recurrence was identified by the history given on the biopsy form by the practitioner.
Received from the Medical College of Virginia, Richmond. * Chief Resident, Department of Oral and Maxillofacial Surgery. t Associate Professor, Department of Oral Pathology. $ Assistant Professor, Departments of Periodontics and Biostatistics. Address correspondence and reprint requests to Dr Kaugars: Department of Oral Pathology, Medical College of Virginia, Box 566, MCV Station, Richmond, VA 23298. 0 1991 American Association geons 0278-2391/91/4903-0009/$3.00/O
of Oral and Maxillofacial
findings
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SWANSON ET AL
Table 2. Radlognphic Diameter of Nasopalatine Duct Cysts (N = 116)
Results Of the 69,988 biopsies accessioned during the period of the study, 334 acceptable cases (0.5%) were identified. Demographic information is presented in Table 1. The overall mean age was 42.5 years, with a range from 9 to 84 years. There was no significant age difference at time of diagnosis between males and females, or blacks and whites. A slight majority, 54%, occurred in males. However, this can be considered a significant sex predilection because only 44.3% of all the submitted biopsies were from males (P = .OOOl). Most patients (93.0%) were white and only 6.0% were black, although 15.3% of all biopsies submitted were from black patients (P = .0065). The mean radiographic diameter was 17.1 mm in 116 cases with which this information was available (Table 2). A small number (6.4%) of cysts were 6 mm or less in diameter, which is within the normal anatomical size range for the incisive cana1.9Y10~‘2 Only one of the eight cysts 6 mm or less in diameter was asymptomatic. There was no correlation between radiographic size of the NPDC and age of the patient. Mean radiographic diameter in whites was smaller than in blacks (P = .0019). Males had a larger mean radiographic diameter than females (P = .0233). The sample size was too small to assess size variations when both race and gender were considered together. Clinical symptoms were common; 52% of patients complained of swelling, 25% had drainage, 20% experienced pain, and 70% of all cases had a combination of these symptoms. Bony expansion was noted in only 1.4% of patients. Palatal numbness, altered or salty taste, or tooth movement was noted in three cases or less in each instance. Up to 29% of patients may have been asymptomatic; howTable 1. Patients Diagnosed With Nasopalatine Duct Cysts (N = 334) Age, mean (yr) Overall Male Female White Black Sex Male Female Race White Black Oriental Not stated * Numbers within parentheses cases.
42.5 43.3 41.5 42.6 38.4 54.2% (181) 45.8% (153) 93.0% (291) 6.0% (20) 1.O% (2) (21) represent the actual number of
Size. mean (mm) Overall Male Female White Black Size, mean (mm) ~6 ( 6.4%) 7-10 (18.6%) 11-15 (25.0%) 16-20 (25.0%) 21-30 (15.0%) 31-50 ( 7.5%) 51-60 ( 2.5%)
17.1 18.9 14.2 16.4 27.8
ever, the information regarding symptoms was not included on the biopsy request form by the practitioner. Symptoms or lack of symptoms was not significantly related to patient age or gender. The presence of symptoms also was not related to radiographic diameter. Histologically, only respiratory epithelium was seen in 9.8% of cases. Respiratory epithelium in combination with one or more other types of epithelium was seen in 18.2%, and 71.8% of lesions had either squamous, columnar, cuboidal, or some combination of these epithelial types but no respiratory epithelium. The type of epithelium present was not related to cyst size. Most biopsy specimens (96.6%) were submitted by oral and maxillofacial surgeons. The remainder were submitted by periodontists, endodontists, and general practitioners. There was no significant difference in lesions removed by surgeons as compared with those removed by other dental practitioners, with one exception: all 10 lesions removed by nonoral and maxillofacial surgeons were asymptomatic . Recurrence was noted in 2% of the cases. No difference was found when comparing cysts that recurred to those that did not. The time between initial treatment and recurrence ranged from 3 months to 6 years. Discussion
Our series of 334 NPDCs comes from a selected sample because all were surgically removed. It is probable that some NPDCs are recognized but are not treated. Because only 57% of the US adult population seeks regular dental care, it is likely that some NPDCs remain undiagnosed.13 Therefore, it is possible that the NPDCs that were surgically removed were not representative of all NPDCs. The NPDC is considered by some to be develop-
270
NASOPALATINEDUCTCYST
The trigger for the prolifermental in origin. 2*3V9*15 ation of epithelial remnants and subsequent cyst formation is unknown. Trauma, bacterial infection, and mucous retention have been suggested and subsequently rejected as mechanisms of cystic pathogenesis. 4,5,7,8,11,12,i6*i7 that a genetic factor may be involved because they found large, rapidly growing NPDCs in young black patients. Spontaneous cystic degeneration of the contents of the incisive canal has been postulated to explain the observation of NPDCs in all ages, including the human fetus.12 The spontaneous cystic degeneration theory seems the most plausible in view of our findings. We found no relationship between patient’s age and lesion size. If the NPDCs were developmental, the size of the lesion would increase as the patient aged. Smaller lesions would be found in young people, and larger lesions would be in older patients. The classification of the NPDC as developmental must be questioned because of the lack of correlation between age and radiographic size. Roper-Hall may have been the tirst to recommend the use of radiographic size in diagnosing NPDCs when he concluded that any radiographic lesion less than 6 mm in diameter should be considered within normal limits.’ This was based partially on the finding that the diameter of the average incisive foramen was approximately 3 mm. However, radiographic magnification, especially in panoramic radiographs, should also be considered. In addition, technical factors such as the angulation of the x-ray beam can alter the apparent radiographic size of a lesion. The presence of symptoms may be an indication for surgical intervention when the radiographic diameter of the lesion is less than 6 mm. Our series had eight cysts of 6 mm or less in diameter, seven of which were asymptomatic. The presence of symptoms was probably the reason that these lesions were removed. Reports of mean radiographic diameter of NPDCs range from 6 to 15 mm. *J~*~*In the present study, the mean diameter of 17.1 mm is larger than those previously reported. The average size of cysts in males was significantly larger than that in females, and the average cyst size in blacks was larger than in whites. One might speculate that larger cysts occur in patients with larger maxillas, or in patients who have a delayed onset of symptoms. Because males seek dental care less freit is plausible that males are quently than femalesI less likely to have asymptomatic NPDCs diagnosed at an early stage. In a similar fashion, blacks seek dental care less frequently than do whites,13 so it is reasonable to expect the mean radiographic size to be larger. A larger size at the time of diagnosis in males might also be related to a delay in the develNofijeeta1'8
suggested
opment of symptoms until the cyst reaches a critical size. Unfortunately, our data did not confirm or disprove any of these theories. Age was not related to size as might be expected for a developmental lesion. The rarity of NPDCs in the first decade of life was somewhat surprising in view of the increasing popularity of panoramic radiography in young patients. A limited potential for growth is demonstrated by the relatively small mean diameter (17.1 mm) and the large number of cases (75%) of cysts that were 20 mm or less in diameter. The relatively limited growth potential is also demonstrated by the finding that only 10% of the NPDCs were greater than 30 mm in diameter. These findings indicate a generalized lack of aggressive behavior and justify observation in selected cases. NPDCs are usually discovered in patients between the fourth and sixth decades of life.2*3*‘2,‘7 The mean age has been reported from 31 to 54 years.8,‘0 In a survey of 70 cysts, one of the largest previous series, Bodin et ali6 reported a mean age of 45 years. In agreement with these studies, our series showed a mean age of 42.5 years, with no significant difference between ages of males or females, and blacks or whites at time of diagnosis. Most of the available literature reports a male predilection for the NPDC. Annaroth et al8 reported a male:female ratio of I .7 to 1 in 35 cases. In a series of 51 cysts, Nortje et al” found 64.7% of the cases in males. Bodin et alI6 reported a similar 67% male predilection in their study of 70 lesions. Abrams et all2 are the only investigators who have reported an almost equal distribution between males and females. In the present study, 54% of the cases occurred in males. However, our biopsy service has more specimens submitted from female patients (56%). If the occurrence of NPDC has no sex predilection, then our series would be expected to show an approximate incidence in males of 44%. With this in mind, our findings suggest a slight male predilection for the NPDC. Goaz et al2 state that NPDCs occur equally in blacks and whites. The series of 70 cysts from Bodin et alI6 were all from white Swedish patients. Nortje et al” believe that blacks are more likely to develop these cysts; however, their study was conducted in a predominantly black South African population. Chamda et al6 studied 960 skulls from South African blacks and stated that the NPDC may occur more frequently in blacks. In our series of 334 NPDCs, 93.0% occurred in whites and only 6.0% in blacks. This may have occurred because whites are more likely to visit a dentist than blacks (59% vs 43%)” and, therefore, are more likely to be treated. The literature indicates that most NPDCs are
SWANSON ET AL
asymptomatic unless secondarily infected. 2.9.7-9,‘7.‘9Symptoms, if present, are so minor that they may be easily tolerated for long periods of time.‘.16 The most common presenting symptoms are swelling, drainage, and pain.8~‘2*‘6*18Tooth movement was noted by one group to occur in 78.4% of the cases.18 It has been stated that larger cysts produce more symptoms,‘6 but others maintain that size is not related to symptoms.8 The percentage of asymptomatic cysts reported ranges from 39% to 50%. ‘.I2 Only 29% were asymptomatic in the present study. It is possible that this is an overestimate because practitioners may not have completed the biopsy request form properly. Over 70% of NPDCs in our series were associated with some combination of swelling, pain, or drainage. Surprisingly, symptoms were not related to radiographic size. Some patients with large lesions had few or no symptoms, whereas some patients with small lesions had severe symptoms. Symptoms were also not related to age. Elderly patients reported the same frequency of symptoms as younger ones. Symptoms were also reported with equal frequency in males and females. It is reasonable to assume that the percentage of asymptomatic NPDCs would be higher in a study based on radiographic evaluation rather than a study of surgical specimens, which are likely to have been removed due to symptoms. Squamous epithelium has been reported in 75% to 82% of NPDCS.~.” Ciliated (respiratory) epithehum has been found in 23% to 42% of these Cysts?~‘~ More than one epithelial type is commanly found.5*” It is generally accepted that the type of epithelium is related to the vertical position within the canal of the cystic degeneration. Squamous metaplasia may account for the preponderante of squamous epithelium seen. In agreement with previous studies, our series showed that 71.8% ofNPDCs have either squamous, columnar, or cuboidal epithelium; 9.8% show respiratory epithelium alone; and 18.2% have both respiratory and squamous type epithelium. Therefore, respiratory epithelium was seen in 28.0% of the lesions. The type of epithelium was not related to cyst size. As expected, 96.6% of the 334 NPDCs were submitted by oral and maxillofacial surgeons. No difference in size by lesions removed by surgeons and other practitioners was seen. Ah 10 NPDCs removed by nonoral surgeons were asymptomatic. This may indicate that these practitioners did not
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record symptoms on the biopsy form or perhaps felt that removal of asymptomatic lesions was indicated. It is generally agreed that NPDCs have a low recurrence rate; reports of recurrence range from 0% to 11%.16 The results of this investigation are consistent with previous studies, showing a recurrence rate of only 2%. Because only seven cysts recurred, it was not possible to determine the characteristics that made them different from cysts that did not recur.
I. Meyer AW: A unique supernumerary paranasal sinus directly above the superior incisors. J Anat 48:118, 1914 2. Goaz PW, White SC: Oral Radiology: Principles and Interpretation. St Louis, MO, MosbyT-1982. pp 443-445 3. Shafer WG. Hine MK. Levv BM: A Textbook of Oral Pathology (ed 4). PhiladelphLa, PA, Saunders, 1983, pp 70-72 4. Stafne EC. Austin LT. Gardner BS: Median anterior maxillary cysts. J Am Dent Assoc 23:801. 1936 5. Allard RHB. Van Der Kwast WAM. Van Der Waal I: Nasopalatine duct cyst. Review of the’literature and report of 22 cases. Int J Oral Surg 10447, 1981 6. Chamda RA. Shear M: Dimensions of incisive fossae on dry skulls and radiographs. Int J Oral Surg 9:452. 1980 7. Camobell JJ. Baden E. Williams AC: Nasopalatine cyst of unusual size: Report of case. J Oral Surg-31:776, 1973 8. Anneroth Cl. Hall G, Stuge U: Nasopalatine duct cyst. Int J Oral Maxillofac Surg 15572, 1986 9. Roper-Hall HT: Cysts of developmental origin in the premaxillary region, with special reference to their diagnosis. J Br Dent Assoc 65:29, 1938 IO. Nortje CJ. Wood RE: The radiologic features of the nasopalatine duct cyst. An analysis of 46 cases. Dentomaxillofac Radio1 17:129, 1988 I I. Brode H, Araiche M: Nasopalatine cyst: Report of a case. J Oral Surg 17&l, 1959 12. Abrams AM, Howell FV, Bullock WK: Nasopalatine cysts. Oral Surg Oral Med Oral Pathol 16:306. 1963 13. National Center for Health Statistics. US Dept. of Health & Human Services: Use of Dental Services and Dental Health, United States, 1986; National Health Survey, Series IO, Number 165; DHHS Publication No. (PHS) 881593, October 1988 14. Pindborg JJ, Kramer IRH. Torloni H: Histological typing of odontogenic tumours, jaw cysts, and allied lesions. World Health Oreanization. Geneva. 1971 15. Choukas NC: Case report of a’median palatine cyst with criteria for a differential diagnosis. Oral Surg Oral Med Oral Pathol 10:237, 1957 16. Bodin I, Isacsson G, Julin P: Cysts of the nasopalatine duct. Int J Oral Maxillofac Surg l5:6%, 1986 17. Hedin M, Klanfeldt A. Persson G: Surgical treatment of nasopalatine duct cysts: A follow-up study. Int J Oral Surg 71427, 1978 18. Nortje CJ, Farman AG: Nasopalatine duct cyst. An aggressive condition in adolescent negroes from south Africa? Int J Oral Surg 7:65, 1978 19. Staretz LR, Brada BJ, Schott TR: Well-defined radiolucent lesion in the maxillary anterior region. J Am Dent Assoc 120:335, 1990
