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Mylohyoid herniation: Gross and histologic evaluation with clinical correlation
Mylohyoid herniation: Gross and histologic evaluation with clinical correlation John D. Engel, Stanton D. Harn. and Donald M. Cohen, Lincoln, Neb. DEPARTMENT
OF ORAL
BIOLOGY,
UNIVERSITY
OF NEBRASKA
MEDICAL
CENTER
The purpose of this study was to further document the presence of a mass herniating inferiorly through the mylohyoid muscle into the submandibular area, to identify the mass histologically, and to discuss its importance in a differential diagnosis of masses in this area. A mass that perforated the mylohyoid muscle was found in 45 of the 100 cadavers studied. These 45 cadavers contained a total of 63 herniations. Of the 60 male cadavers, 26 (43.33%) showed herniation, and 19 (47.50%) of the 40 female cadavers showed herniation. Histologic evaluation of the 63 biopsy specimens revealed the following: 30 herniating masses (47.61%) were of the sublingual gland; 26 (44.44%) were of the submandibular gland; 4 (6.34%) were composed of pure adipose tissue, and 1 (1.56%) was a cholesteatoma. Inflammation was found in 46 (73.00%) of the biopsy specimens, consisting of sclerosing sialoadenitis in 30 specimens (47.61%) and a mild chronic inflammatory infiltrate in 16 specimens (25.39%). (ORAL SURG. ORAL MED. ORAL PATHOL.. 1987;63:55-9)
S
ublingual gland perforation of the mylohyoid muscle (sublingual gland herniation) exists with greater frequency than was once thought. Nathan and Luchansky’ found that 42% of the cadavers they studied had a deficiency or hiatus in the mylohyoid muscle. Gaughran2 found that 36.1% of the “halfheads” studied had a massthat projected through the
mylohyoid muscle-a so-called “mylohyoid boutonn&e” or “sublingual bouton.” In ai anatomic exploration of the paralingual space, Castelli and coworkers3found that 10%of the cadavers they studied had a large projection of the sublingual gland into the suprahyoid region. The purpose of this study was to document and evaluate mylohyoid herniation by
Fig. 1. Example of left-sided large herniating mass (Hm) passing inferiorly with submental artery (A/ through mylohyoid muscle into submandibular region. Sm, Submandibular gland. M, Mandible. D, Anterior belly of digastric muscle. Mh, Mylohyoid muscle. H, Hyoid bone. Omohyoid muscle has been moved superiorly adjacent to submandibular gland. 55
56
Engel, Harn, and Cohen
Oral Surg. January, 1987
Fig. 2. Frontal view showing submandibular region containing bilateral herniating masses(Hm). Masses this size would be palpable during a routine head and neck examination M, Mandible. Sm, Submandibular gland. D, Anterior belly of digastric muscle. Mh, Mylohyoid muscle.
Table I. Distribution of herniations in 100 cadavers No. of herniations 100 Cadavers
Male Female Total *Double herniatim
Unilateral right
Unilateral left
(46?5%) 8
(26.;2%) 1
-(42.10%)
- (5.26%)
(36,i4%)
(442404%)
(lG7%)
(31:141%)
Bilateral
Unilateral double right
-
26 19
Unilateral double left
Double bilateral
-
(lO.iza) -
45 (4.i4%)
Other
-
1* (5.26%)
1* (2.22%)
on left side with a concurrent single herniatian on right side
using gross and histologic methods. A differential diagnosis of massesin this region was included to aid the clinician considering treatment of submandibular masses. MATERIALS AND METHODS
The submandibular region of 100 adult cadavers (60 male, 40 female) was dissected bilaterally and evaluated for a sublingual gland herniation. The dimensions of the herniating masseswere measured according to their greatest height (inferior surface of mylohyoid muscle to inferior surface of mass), greatest length (anteroposterior dimension), and greatest width (mediolateral dimension). The position of the herniating mass within the muscle was recorded by measuring from the posterior aspect of the hiatus to the posterior border of the mylohyoid muscle. Biopsies of the masseswere then done, and the specimens were submitted for microscopic evaluation.
RESULTS
A massthat perforated the mylohyoid muscle was found in 45 of the 100 cadaversstudied (Figs. 1 to 3). Among these 45 cadavers, a total of 63 herniations were found (Table I). The average dimensions of the masseswere 12.69 mm anteroposteriorly (range 3 to 21 mm), 8.37 mm superoinferiorly (range 5 to 28 mm), and 5.15 mm mediolaterally (range 3 to 12 mm). The average distance from the posterior border of the mylohyoid muscle was found to be 16.74 mm (range 5 to 28 mm). The anteroposterior -length of the mylohyoid muscle is approximately 40 mm. The majority of the masseshad their lateral borders in contact with the medial surface of the mandible. All masses were enveloped by mylohyoid fascia that extended from the inferior surface of the mylohyoid muscle. The positions of the submental artery and vein and the mylohyoid nerve were found to have no definite
Volume63 Number 1
Mylohyoid herniation
57
Fig. 3. Inferior view of submandibular region showing example of unilateral double herniation through mylohyoid muscle. The anterior projection is an adipose globule (F) and the posterior projection is a massof salivary gland tissue (Sg). Sm, Submandibular gland. M, Mandible. Mh, Mylohyoid muscle.
Fig. 4. Normal submandibular gland showing predominance of serous acini (S) and few isolated nests of lighter staining mucous acini (kf). Also note ductal structures (D). Fig. 5. Normal sublingual gland showing area composedentirely of light-staining mucous acini with few ducts. Fig. 6. Salivary gland with sclerosing sialoadenitis showing increased amount of hyalinized stromal elements, fatty deposits in interlobular areas, and almost total absenceof glandular acini. Residual ductal elements predominate with many containing inspissated material. Fig. 7. Chronic inflammatory infiltrate within otherwise normal area of sublingual gland.
relationship with the herniation, although it was observed that they occasionally passed through the muscle along with the herniation. Histologic evaluation (Figs. 4 to 8) revealed that
30 (47.6 1%) of the herniating masseswere composed predominantly of mucous-type salivary gland tissue (sublingual gland), 28 (44.44%) were of the mixed mucous-seroustype with serous predominance (sub-
58
Engel, Ham, and Cohen
Fig.
Oral Surg. January, 1987
8. Cholesteatoma
showing characteristic
mandibular gland), 4 (6.34%) were composed of pure adipose tissue, and 1 (1.58%) was diagnosed as a cholesteatoma. Inflammation was found in 46 (73.00%) of the specimens,consisting of a sclerosing sialoadenitis in 30 specimens (47.61%) and a mild chronic inflammatory infiltrate in 16 specimens (25.39%). DBCUSSION
In the present study, mylohyoid herniations were found in 45% of the cadavers studied. No mention is made in either the Gaughran study2 or the Nathan and Luchansky study’ of the histologic composition of the glandular mylohyoid herniations. This study determined that these herniations are not specifically sublingual gland herniations in all cases,as implied by the other authors. Thirty (48%) of the specimens were predominantly mucous-type salivary gland tissue suggestive of sublingual gland, and 28 (44%) were of a mixed mucous-serous type with serous predominance suggestive of submandibular gland tissue. Significant inflammation was found in 73% of the cadaver specimens. It is not known whether this inffammation precipitated the glandular herniation or if the herniation is, in fact, a developmental defect. It is thought that the specimens composed of sublingual tissue represent herniated projections of the sublingual gland. The specimens composed of submandibular salivary tissue represent either a forward projection of the deep process of the submandibular gland that herniated inferiorly or ectopic
cholesterol clefts,
submandibular gland tissueh6that developed inferiorly and herniated through the myiohyoid muscle. The wide range of the dimensions of the masses shows there is a great size variation in mylohyoid herniation. We believe that approximately 25% of the massescould be readily palpated becauseof their large size (Figs. 1 and 2). The fact that herniation occurred in 45% of the cadavers studied makes the entity a significant factor when one is considering a differential diagnosis of a mass in the submandibular region. A differential diagnosis for swellings or palpable massesof the submandibular region would include tumors and inflammatory conditions of the submandibular and sublingual salivary glands; neoplastic and inflammatory conditions of the submandibular iymph nodes; adnexal tumors; granulomatous diseases;neoplasms arising from nerves, blood vessels, and adipose tissue; and assortedbranchiogenic developmental anomalies.7-9 According to Worphea,” a mass in this area may be assumedto be an enlarged lymph node if it is not determined to be originating in the submandibular gland. In the present study, 45% of the cadavers had a mass in this region that clearly did not arise from the submandibular gland or lymph nodes (Figs. 2 and 3). Forty-four percent of these masses were composedof ectopic submandibular gland tissue and 48% were composed of sublingual salivary gland tissue. This massis the so-called “mylohyoid boutonniere,” and this entity is a significant addition to the list of lesions that would normally appear in the
Mylohyoid
Volume 63 Number I
differential diagnosis for masses of the submandibular region. The authors wish to thank Deb McVey, Eddie Manning, and Phyllis Kumm for their help in preparation of the manuscript. The authors are also appreciative of Tom Gessner, Larry Sheffield, and Kim Theesen for their photographic and illustration expertise. REFERENCES
1. Nathan H, Luchansky E: Sublingual gland herniation through the mylohyoid muscle. ORAL SURG ORAL MED ORAL ton. J Anat 97: 565-568, 1963. 3. Castelli WA, Huelke DF, Celis A: Some basic anatomic features in paralingual space surgery. ORAL SURG ORAL MED ORAL PATHOL, 27: 613-621, 1969. 4. Bronstein SL, Clark MS: Sublingual gland salivary fistula and sialocele. ORAL SURG ORAL MED ORAL PATHOL, 57: 356-361. 1984.
59
Roman0 JF, Marino CT: Heterotopic salivary tissue at the base of the neck. Int J Dermatol 21: 42-43, 1982. Saucy P: Congenital cervical salivary fistula. Can J Surg 28: 130-131, 1985. Braun TW, SotereanosGC: Cervical ranula due to an ectopic sublingual gland. J Oral Maxillofac Surg 10: 56-58, 1982. Laskin JL. Hvlton RP. Stern M. Hornunn N: Soft tissue lesion of the sublingual and submandibular region. J Oral Maxillofac Surg 42: 453-458, 1984. 9. Mandel L, Baurmash H: Ranulae. ORAL SURG ORAL MED ORAL PATHOL 10: 567-574, 1957.
10. Worphea RL: Textbook of differential diagnosis of oral lesions, ed. 2, St. Louis, 1980,The C.V. Mosby Company, pp. 266-287.
PATHOL 59: 21-23, 1985. 2. Gaughran GR: Mylohyoid boutonniere and sublingual bou-
herniation
Reprint requests to:
Dr. Stanton D. Harn Department of Oral Biology University of Nebraska Medical Center College of Dentistry Lincoln. NE 68583-0740
OF ORAL
BIOLOGY,
UNIVERSITY
OF NEBRASKA
MEDICAL
CENTER
The purpose of this study was to further document the presence of a mass herniating inferiorly through the mylohyoid muscle into the submandibular area, to identify the mass histologically, and to discuss its importance in a differential diagnosis of masses in this area. A mass that perforated the mylohyoid muscle was found in 45 of the 100 cadavers studied. These 45 cadavers contained a total of 63 herniations. Of the 60 male cadavers, 26 (43.33%) showed herniation, and 19 (47.50%) of the 40 female cadavers showed herniation. Histologic evaluation of the 63 biopsy specimens revealed the following: 30 herniating masses (47.61%) were of the sublingual gland; 26 (44.44%) were of the submandibular gland; 4 (6.34%) were composed of pure adipose tissue, and 1 (1.56%) was a cholesteatoma. Inflammation was found in 46 (73.00%) of the biopsy specimens, consisting of sclerosing sialoadenitis in 30 specimens (47.61%) and a mild chronic inflammatory infiltrate in 16 specimens (25.39%). (ORAL SURG. ORAL MED. ORAL PATHOL.. 1987;63:55-9)
S
ublingual gland perforation of the mylohyoid muscle (sublingual gland herniation) exists with greater frequency than was once thought. Nathan and Luchansky’ found that 42% of the cadavers they studied had a deficiency or hiatus in the mylohyoid muscle. Gaughran2 found that 36.1% of the “halfheads” studied had a massthat projected through the
mylohyoid muscle-a so-called “mylohyoid boutonn&e” or “sublingual bouton.” In ai anatomic exploration of the paralingual space, Castelli and coworkers3found that 10%of the cadavers they studied had a large projection of the sublingual gland into the suprahyoid region. The purpose of this study was to document and evaluate mylohyoid herniation by
Fig. 1. Example of left-sided large herniating mass (Hm) passing inferiorly with submental artery (A/ through mylohyoid muscle into submandibular region. Sm, Submandibular gland. M, Mandible. D, Anterior belly of digastric muscle. Mh, Mylohyoid muscle. H, Hyoid bone. Omohyoid muscle has been moved superiorly adjacent to submandibular gland. 55
56
Engel, Harn, and Cohen
Oral Surg. January, 1987
Fig. 2. Frontal view showing submandibular region containing bilateral herniating masses(Hm). Masses this size would be palpable during a routine head and neck examination M, Mandible. Sm, Submandibular gland. D, Anterior belly of digastric muscle. Mh, Mylohyoid muscle.
Table I. Distribution of herniations in 100 cadavers No. of herniations 100 Cadavers
Male Female Total *Double herniatim
Unilateral right
Unilateral left
(46?5%) 8
(26.;2%) 1
-(42.10%)
- (5.26%)
(36,i4%)
(442404%)
(lG7%)
(31:141%)
Bilateral
Unilateral double right
-
26 19
Unilateral double left
Double bilateral
-
(lO.iza) -
45 (4.i4%)
Other
-
1* (5.26%)
1* (2.22%)
on left side with a concurrent single herniatian on right side
using gross and histologic methods. A differential diagnosis of massesin this region was included to aid the clinician considering treatment of submandibular masses. MATERIALS AND METHODS
The submandibular region of 100 adult cadavers (60 male, 40 female) was dissected bilaterally and evaluated for a sublingual gland herniation. The dimensions of the herniating masseswere measured according to their greatest height (inferior surface of mylohyoid muscle to inferior surface of mass), greatest length (anteroposterior dimension), and greatest width (mediolateral dimension). The position of the herniating mass within the muscle was recorded by measuring from the posterior aspect of the hiatus to the posterior border of the mylohyoid muscle. Biopsies of the masseswere then done, and the specimens were submitted for microscopic evaluation.
RESULTS
A massthat perforated the mylohyoid muscle was found in 45 of the 100 cadaversstudied (Figs. 1 to 3). Among these 45 cadavers, a total of 63 herniations were found (Table I). The average dimensions of the masseswere 12.69 mm anteroposteriorly (range 3 to 21 mm), 8.37 mm superoinferiorly (range 5 to 28 mm), and 5.15 mm mediolaterally (range 3 to 12 mm). The average distance from the posterior border of the mylohyoid muscle was found to be 16.74 mm (range 5 to 28 mm). The anteroposterior -length of the mylohyoid muscle is approximately 40 mm. The majority of the masseshad their lateral borders in contact with the medial surface of the mandible. All masses were enveloped by mylohyoid fascia that extended from the inferior surface of the mylohyoid muscle. The positions of the submental artery and vein and the mylohyoid nerve were found to have no definite
Volume63 Number 1
Mylohyoid herniation
57
Fig. 3. Inferior view of submandibular region showing example of unilateral double herniation through mylohyoid muscle. The anterior projection is an adipose globule (F) and the posterior projection is a massof salivary gland tissue (Sg). Sm, Submandibular gland. M, Mandible. Mh, Mylohyoid muscle.
Fig. 4. Normal submandibular gland showing predominance of serous acini (S) and few isolated nests of lighter staining mucous acini (kf). Also note ductal structures (D). Fig. 5. Normal sublingual gland showing area composedentirely of light-staining mucous acini with few ducts. Fig. 6. Salivary gland with sclerosing sialoadenitis showing increased amount of hyalinized stromal elements, fatty deposits in interlobular areas, and almost total absenceof glandular acini. Residual ductal elements predominate with many containing inspissated material. Fig. 7. Chronic inflammatory infiltrate within otherwise normal area of sublingual gland.
relationship with the herniation, although it was observed that they occasionally passed through the muscle along with the herniation. Histologic evaluation (Figs. 4 to 8) revealed that
30 (47.6 1%) of the herniating masseswere composed predominantly of mucous-type salivary gland tissue (sublingual gland), 28 (44.44%) were of the mixed mucous-seroustype with serous predominance (sub-
58
Engel, Ham, and Cohen
Fig.
Oral Surg. January, 1987
8. Cholesteatoma
showing characteristic
mandibular gland), 4 (6.34%) were composed of pure adipose tissue, and 1 (1.58%) was diagnosed as a cholesteatoma. Inflammation was found in 46 (73.00%) of the specimens,consisting of a sclerosing sialoadenitis in 30 specimens (47.61%) and a mild chronic inflammatory infiltrate in 16 specimens (25.39%). DBCUSSION
In the present study, mylohyoid herniations were found in 45% of the cadavers studied. No mention is made in either the Gaughran study2 or the Nathan and Luchansky study’ of the histologic composition of the glandular mylohyoid herniations. This study determined that these herniations are not specifically sublingual gland herniations in all cases,as implied by the other authors. Thirty (48%) of the specimens were predominantly mucous-type salivary gland tissue suggestive of sublingual gland, and 28 (44%) were of a mixed mucous-serous type with serous predominance suggestive of submandibular gland tissue. Significant inflammation was found in 73% of the cadaver specimens. It is not known whether this inffammation precipitated the glandular herniation or if the herniation is, in fact, a developmental defect. It is thought that the specimens composed of sublingual tissue represent herniated projections of the sublingual gland. The specimens composed of submandibular salivary tissue represent either a forward projection of the deep process of the submandibular gland that herniated inferiorly or ectopic
cholesterol clefts,
submandibular gland tissueh6that developed inferiorly and herniated through the myiohyoid muscle. The wide range of the dimensions of the masses shows there is a great size variation in mylohyoid herniation. We believe that approximately 25% of the massescould be readily palpated becauseof their large size (Figs. 1 and 2). The fact that herniation occurred in 45% of the cadavers studied makes the entity a significant factor when one is considering a differential diagnosis of a mass in the submandibular region. A differential diagnosis for swellings or palpable massesof the submandibular region would include tumors and inflammatory conditions of the submandibular and sublingual salivary glands; neoplastic and inflammatory conditions of the submandibular iymph nodes; adnexal tumors; granulomatous diseases;neoplasms arising from nerves, blood vessels, and adipose tissue; and assortedbranchiogenic developmental anomalies.7-9 According to Worphea,” a mass in this area may be assumedto be an enlarged lymph node if it is not determined to be originating in the submandibular gland. In the present study, 45% of the cadavers had a mass in this region that clearly did not arise from the submandibular gland or lymph nodes (Figs. 2 and 3). Forty-four percent of these masses were composedof ectopic submandibular gland tissue and 48% were composed of sublingual salivary gland tissue. This massis the so-called “mylohyoid boutonniere,” and this entity is a significant addition to the list of lesions that would normally appear in the
Mylohyoid
Volume 63 Number I
differential diagnosis for masses of the submandibular region. The authors wish to thank Deb McVey, Eddie Manning, and Phyllis Kumm for their help in preparation of the manuscript. The authors are also appreciative of Tom Gessner, Larry Sheffield, and Kim Theesen for their photographic and illustration expertise. REFERENCES
1. Nathan H, Luchansky E: Sublingual gland herniation through the mylohyoid muscle. ORAL SURG ORAL MED ORAL ton. J Anat 97: 565-568, 1963. 3. Castelli WA, Huelke DF, Celis A: Some basic anatomic features in paralingual space surgery. ORAL SURG ORAL MED ORAL PATHOL, 27: 613-621, 1969. 4. Bronstein SL, Clark MS: Sublingual gland salivary fistula and sialocele. ORAL SURG ORAL MED ORAL PATHOL, 57: 356-361. 1984.
59
Roman0 JF, Marino CT: Heterotopic salivary tissue at the base of the neck. Int J Dermatol 21: 42-43, 1982. Saucy P: Congenital cervical salivary fistula. Can J Surg 28: 130-131, 1985. Braun TW, SotereanosGC: Cervical ranula due to an ectopic sublingual gland. J Oral Maxillofac Surg 10: 56-58, 1982. Laskin JL. Hvlton RP. Stern M. Hornunn N: Soft tissue lesion of the sublingual and submandibular region. J Oral Maxillofac Surg 42: 453-458, 1984. 9. Mandel L, Baurmash H: Ranulae. ORAL SURG ORAL MED ORAL PATHOL 10: 567-574, 1957.
10. Worphea RL: Textbook of differential diagnosis of oral lesions, ed. 2, St. Louis, 1980,The C.V. Mosby Company, pp. 266-287.
PATHOL 59: 21-23, 1985. 2. Gaughran GR: Mylohyoid boutonniere and sublingual bou-
herniation
Reprint requests to:
Dr. Stanton D. Harn Department of Oral Biology University of Nebraska Medical Center College of Dentistry Lincoln. NE 68583-0740