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Epithelial-myoepithelial carcinoma: An immunocytochemical study
Epithelial-myoepithelial carcinoma: An . im.munocytochemical study Richard M. Palmer, Ph.D., B.D.S., F.D.S.R.C.S., London, England ROYAL
DENTAL
HOSPITAL
An immunocytochemical study of epithelial-myoepithelial carcinoma, using antibodies to smooth muscle myosin, keratins, and type IV collagen, is presented. This rare tumor of salivary gland is composed of tubules and ductal structures, comprising an outer layer of clear cells that show myoepithelial differentiation and an inner layer of eosinophilic cells that show ductal differentiation. The findings in this study correlate well with previous ultrastructural descriptions of this tumor. (ORAL SURG. ORAL MED. ORAL PATHOL. 59~511-515,
1985)
E
pithelial-myoepithelial carcinoma was the term used by Donath and co-workers’ in 1972 to describe a distinctive but rare tumor of salivary glands. Earlier cases had been described as glycogen-rich clear cell adenoma.,21 3 glycogen-rich reticulated adenoma, clear cell myoepithelial adenoma,5and adenomyoepithelioma.6 The parotid1gland is the most frequent site of this tumor, and there appears to be a predominance among female patients. It is most common in elderly patients, and the maximum frequency is in the seventh decade. It has a most characteristic histologic appearance, consisting of two distinctive cell types forming doubl.e-layered ductal or tubular structures. The inner cell layer is composedof eosinophilic cells that resemble intercalated duct cells, and the outer clear cells have been described as myoepithelial.‘-5, ‘, * Several reports, which have included ultrastructural descriptions offthese cell types, support this .view.‘,5x6 In some cases,however, the lack of optimal fixation and processing of the tissue hals not allowed definite proof of myoepithelial cell participation. More recently, immunocyt’ochemical techniques using antibodies to actin, myosin, and intermediate filament proteins have enabled workers to distinguish between cells that show various differentiation pathways in salivary gland tumors.9-‘3 These techniques have therefore been applied to a case of epithelial-:myoepithelial carcinoma in order to confirm or refute previous ultrastructural descriptions. MATERIAL
AND METHOD
The tumor ‘wasremoved from the parotid gland of an 83-year-old woman. The tissue was fixed in methacarn (60% methanol, 30% chloroform, 10%
acetic acid), as this fixative has been shown to permit successful immunoenzyme staining on paraffin-processedtissue with the antibodies used in the present study.13 The specimen was dehydrated through ascending concentrations of alcohol, cleared in chloroform, and impregnated in paraffin wax. Sections were dewaxed in xylene and absolute ethanol, rehydrated through descending concentrations of alcohol, and equilibrated in phosphate-buffered saline solution. l.mmunocytochemical staining was performed, as described previously’4 using alkaline phosphataseconjugated secondary antibodies (Sigma) with the following primary antibodies: 1. Antibody to smooth muscle myosin, raised in rabbits and previously shown to stain myoepithelial cells in normal glands.13x l5 2. Antibody to human callus prekeratin, raised in rabbits and previously shown to stain duct cells in normal glands.13,‘* 3. Monoclonal antibody (16a) to a 45/46K keratin doublet previously shown to stain cells in a basal location in normal salivary gland ducts.13 4. Monoclonal antibody to type IV collagen previously shown to stain basement membranes.‘3s’6 Immunoenzyme activity was detected with fast red/sodium naphthol substrate solution. To test for specificity of staining, control sections were incubated with preimmune sera. Staining was also demonstrated to be extinguished by prior absorption of the antibodies with the appropriate antigen. All ‘controls were negative. RESULTS
The tumor was composed of tubules and ductal structures consisting of an inner layer of eosinophilic 511
512
Palmer
Ora! Surg. May, 1985
Fig. 1. Immunoenzyme staining with anti-smooth-muscle myosin showing several positively stained clear cells in the outer layer of the ductai structures, (Original magnification, x500.)
Fig. 2. Immunoenzyme staining with anticallus keratin showing positive staining of the inner layer of duct cells. (Original magnification, X300.)
cells and an outer layer of clear cells. In some areas the clear cells predominated. Immunocytochemistry with anti-smooth muscle myosin produced staining of many of the clear cells (Fig. 1). The inner layer of ductal cells stained with the anticallus prekeratin (Fig. 2). Ail cells gave negative reactions to staining with the monoclonal keratin 16a (Fig. 3). Basement membranes outlining the ductal structures were stained with the anti-type
IV collagen (Fig. 4). These basement membranes often appeared to be duplicated. DlSClJSSlc9N The immunocytochemical results presented in this study correlate well with previous ultrastructural descriptions of this tumor. The inner layer of cells have been described as similar to intercalated duct cells and possesstonofilaments, desmosomes,luminal
Volume Number
59 5
Epithelial-myoepithelial
carcinoma
513
Fig. 3. Immunoenzyme staining with monoclonal antikeratin 16a, showing no staining of both cell types. (Original magnification, X300.)
Fig. 4. Immunoenzyme staining with monoclonal anti-type IV collagen showing staining of replicated basement membranes. (Original magnification, x300.)
microvilli, and some cytoplasmic vesicles7 The immunocytochemical staining observed with anticallus prekeratin would support this view, as intercalated ducts in the normal gland are positive with this antibody. However, cells of the striated and excretory ducts are also positively stained,13and therefore immtmocytochemistry would not exclude the possibility that these cells may be found in the tumor. The tumor ductal cells did not stain with the monoclonal keratin 16a, and tlherefore it is unlikely that these
cells are similar in their differentiation to basally located cells in the normal gland.13The suggestion that the ductal cells are most akin to intercalated duct cells probably arises from their relationship to the proposed myoepithelial clear cells, a relationship that exists in normal glands.17 Many of the outer clear cells were positive for smooth muscle myosin, and all clear cells were negative for both keratins, suggesting a myoepithelial rather than ductal differentiation. This is, therefore,
514
Palmer
in agreement with the ultrastructure.‘, ’ It has been shown previously that the antimyosin is a very specific label for myoepithelial cells in normal glands and that only tumor cells exhibiting considerable myoepithelial differentiation are stained.13It is possible, therefore, that the clear cells in this tumor show varying degrees of myoepithelial differentiation, so that only a proportion of them are positive for myosin. This correlates well with the suggestion that the clear cells in this tumor are similar to the clear ctll myoepithelial precursors described by Tandler in human submandibular glands.7,‘7It must be realized, however, that it is not always possible to equate cells that appear as clear cells on light microscopic sections with thosethat appear electronlucent at the ultrastructural level. Moreover, clear cells have been described asvariants of many additional cell types, in addition to myoepithelial cells, in salivary gland tumors.” A multilayered complex basal lamina at the stromal-epithelial interface has been described by Corio and co-workers,’ and this finding was substantiated with the demonstration of type IV collagen in the same location. The presence of a basal lamina has been proposed as further evidence of myoepithedial differentiation, but this cannot be considered as specific. It has been suggestedthat epithelial-myoepithelial carcinoma is a variant of pleomorphic adenoma but that it is sufficiently well defined to merit individual classification.2-5The behavior of this tumor would certainly suggest that it is a separate entity because, in comparison to pleomorphic adenoma, it is more infiltrative and destructive, has a propensity for recurrences following surgical excision, and shows a tendency toward perineural involvement and iemote metastases.2,7’B The results of the present immunocytochemical study would also confirm that this tumor is quite distinct from pleomorphic adenoma. In a similar study of pleomorphic adenoma, using the same antibodies, the outer layer of cells in the double-layered ductal structures were always negative for smooth muscle myosin.13This fact may be of some diagnostic benefit. The evidence given for the cell types involved and the particular behavior of this tumor would seemto indicate that the term epithelial-myoepithelial carcinoma is most appropriate. The precursor cells of the intercalated ducts have beenimplicated in the histogenesisof this tumor. Thus, it is proposed that they give rise to both duct and myoepithelial cells, as suggested for other salivary Alternatively, the recent hypothesis gland tumors. 19,*0 proposed by Dardick and co-workers,2“22implicating neoplasia of a complete ductal/myoepithelial unit in the histogenesis of pleomorphic adenoma, could also be applied to epithelial-myoepithelial carcinoma.
Oral Surg. May, 1985
I wish to thank Dr. B.A.
Gusterson of the Ludwig
Institute for Cancer Research,London, England, for his help with this study. REFERENCES 1. Donath K, Seifert G, Schmitz R: Zur Diagnose und Ultrastruktur des tubularen Speichelgangcarcinoms. Epithelialmyoepitheliales Schalstuckcarcinom. Virchows Arch (Pathol Anat) 356: 16-31, 1972. Corridan M: Glycogen rich clear cell adenoma of the parotid gland. J Path01 Bacterial 72: 623-626, 1956. Goldman RL, Klein HZ: Glycogen-rich adenoma of the carotid gland. Cancer 30: 749-754, 1972. ‘Feyrter,-F.: ijber das glycogenreiche retikulierte Adenom der Speicheldrusen. Z Krebsforsch 65: 446-454, 1963. Saksela E, Tarkkanen J, Wartiovaara J: Parotid clear-cell adenoma of possible myoepitheliai origin. Cancer 30: 742748, 1972. (cylindroma) of 6. Bauer WH, Fox RA: Adenomyoepithelioma palatal mucous glands. Arch Path01 39: 96-102, 1945. I. Corio RL, Sciubba JJ, Brannon RB, Batsakis JG: Epithelialmyoepithelial carcinoma of intercalated duct origin. ORAL SURC ORAL MED ORAL PATHOL 93: 280-287,
! 982
8. Chen KTK: Clear cell carcinoma of the salivary gland. Hum Pathol 14: 91-93, 1983. 9. Caselitz J. LoninE T: Soecific demonstration of actin and keratin filaments-in plekmorphic adenomas by means of immunoelectronmicroscopy. Virchows Arch (Path01 Anat) 393: 153-158, 1981. IO. Caselitz J, Loning T, Staquet MJ, Seifert 6, Thivolet J: lmmunocytochemical demonstration of filamentous structures in the parotid gland: occurrence of keratin and actin in normal and tumoral parotid gland with speciai respect to the myoepithelial cells. J Cancer Res Clin Onto! 100: 59-68, 1981. 11. Caselitz J, Osborn M, Seifert G, Weber K: Intermediate sized filament proteins (Prekeratin, vimentin, desmin) in the normal parotid gland and parotid gland tumours: immunofluorescence study. Virchows Arch (Path01 Anat) 393: 273-286, 1981. 12. Krepler R, Denk HJ, Artlieb U, Mall R: Immunocytochemistry of intermediate fiiament proteins present in pleomorphic adenomas of the human parotid gland: characterization of different cell types in the same tumor. Differentiation 21: 191-199, 1982. 13. Palmer RM, Lucas RB, Knight J, Gusterson B: Immunocytochemical identification of cell types in pleomorphic adenoma, with particular reference to myoepithelial cells. J Path01 (in press, 1985). 14. Mitchell D, Gusterson BA: Simultaneous demonstration of keratin and mucin. J Histochem Cytochem 30: 707-709, 1982. MJ, Mitchell D, Ellison M, 15. Gusterson BA, Warburton Neville AM, Rudland PS: Distribution of myoepithelial cells and basement membrane proteins in the normal breast and benign and malignant breast disease. Cancer Res 42: 47634770, 1982. 16. Gusterson BA, Warburton MJ, Mitchell D, Kraft N, Hancock WW: Invading squamous cell carcinoma can retain a basal lamina: An immunohistochemical study using a monocionai antibody. Lab Invest 51: 82-87, 1984. 17. Tandler B: Ultrastructure of the human submaxillary gland. III. Myoepithelium. Z Zellforsch 68: 852-863. 1965. 18. Seifert G. Donath K: iiber das Vorkommen SOQ.heller Zellen in Speicheldrusen-tumoren: Ultrastruktur unld Differentialdiagnose. Z Krebsforsch 91: 165-182. 1978. 19. Eversole LR: Histogenetic classification of salivary tumours. Arch Path01 92: 433-443, 1971. 20. Regezi JA, Batsakis JG: Histogenesis of salivary gland neoplasms. Otolaryngol Clin North Am 10: 297-307, 1977. 21. Dardick I, Van Norstrand AWP, Jeans MTD Rippstein P,
Epithelial-myoepithelial
Volume 59 Number 5 Edwards V: Pleomorphic adenoma. I. Ultrastructural organization of “epithelial” regions. H[um Path01 14: 780-797, 1983. 22. Dardick I, Van Norstrand AWP, Jeans MTD, Rippstein P, Edwards V: Pleomorphic adenoma. II. Ultrastructural organization of “stromal” regions. Hum Path01 14: 798809, 1983.
BOUND
VOLUMES
AVAILABLE
carcinoma
Reprint requests to: Dr. Richard M. Palmer Royal Dental Hospital Leicester Square London WC2H 7LJ, England
TO SUBSCRIBERS
Bound volumes of ORAL SURGERY, ORAL MEDICINE and ORAL PATHOLOGY are available to subscribers (only) for the 1985 issues from the Publisher, at a cost of $36.75 ($47.75 international) for Vmol.59 (January-June) and Vol. 60 (July-December). Shipping charges are included. Each bound volume contains a subject and author index and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact The C. V. Mosby Company, Circulation Department, 11830 Westline Industrial Drive, St. Louis, Missouri 63146, USA; phone (800) 325-4177, ext. 351. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular journal subscription.
515
DENTAL
HOSPITAL
An immunocytochemical study of epithelial-myoepithelial carcinoma, using antibodies to smooth muscle myosin, keratins, and type IV collagen, is presented. This rare tumor of salivary gland is composed of tubules and ductal structures, comprising an outer layer of clear cells that show myoepithelial differentiation and an inner layer of eosinophilic cells that show ductal differentiation. The findings in this study correlate well with previous ultrastructural descriptions of this tumor. (ORAL SURG. ORAL MED. ORAL PATHOL. 59~511-515,
1985)
E
pithelial-myoepithelial carcinoma was the term used by Donath and co-workers’ in 1972 to describe a distinctive but rare tumor of salivary glands. Earlier cases had been described as glycogen-rich clear cell adenoma.,21 3 glycogen-rich reticulated adenoma, clear cell myoepithelial adenoma,5and adenomyoepithelioma.6 The parotid1gland is the most frequent site of this tumor, and there appears to be a predominance among female patients. It is most common in elderly patients, and the maximum frequency is in the seventh decade. It has a most characteristic histologic appearance, consisting of two distinctive cell types forming doubl.e-layered ductal or tubular structures. The inner cell layer is composedof eosinophilic cells that resemble intercalated duct cells, and the outer clear cells have been described as myoepithelial.‘-5, ‘, * Several reports, which have included ultrastructural descriptions offthese cell types, support this .view.‘,5x6 In some cases,however, the lack of optimal fixation and processing of the tissue hals not allowed definite proof of myoepithelial cell participation. More recently, immunocyt’ochemical techniques using antibodies to actin, myosin, and intermediate filament proteins have enabled workers to distinguish between cells that show various differentiation pathways in salivary gland tumors.9-‘3 These techniques have therefore been applied to a case of epithelial-:myoepithelial carcinoma in order to confirm or refute previous ultrastructural descriptions. MATERIAL
AND METHOD
The tumor ‘wasremoved from the parotid gland of an 83-year-old woman. The tissue was fixed in methacarn (60% methanol, 30% chloroform, 10%
acetic acid), as this fixative has been shown to permit successful immunoenzyme staining on paraffin-processedtissue with the antibodies used in the present study.13 The specimen was dehydrated through ascending concentrations of alcohol, cleared in chloroform, and impregnated in paraffin wax. Sections were dewaxed in xylene and absolute ethanol, rehydrated through descending concentrations of alcohol, and equilibrated in phosphate-buffered saline solution. l.mmunocytochemical staining was performed, as described previously’4 using alkaline phosphataseconjugated secondary antibodies (Sigma) with the following primary antibodies: 1. Antibody to smooth muscle myosin, raised in rabbits and previously shown to stain myoepithelial cells in normal glands.13x l5 2. Antibody to human callus prekeratin, raised in rabbits and previously shown to stain duct cells in normal glands.13,‘* 3. Monoclonal antibody (16a) to a 45/46K keratin doublet previously shown to stain cells in a basal location in normal salivary gland ducts.13 4. Monoclonal antibody to type IV collagen previously shown to stain basement membranes.‘3s’6 Immunoenzyme activity was detected with fast red/sodium naphthol substrate solution. To test for specificity of staining, control sections were incubated with preimmune sera. Staining was also demonstrated to be extinguished by prior absorption of the antibodies with the appropriate antigen. All ‘controls were negative. RESULTS
The tumor was composed of tubules and ductal structures consisting of an inner layer of eosinophilic 511
512
Palmer
Ora! Surg. May, 1985
Fig. 1. Immunoenzyme staining with anti-smooth-muscle myosin showing several positively stained clear cells in the outer layer of the ductai structures, (Original magnification, x500.)
Fig. 2. Immunoenzyme staining with anticallus keratin showing positive staining of the inner layer of duct cells. (Original magnification, X300.)
cells and an outer layer of clear cells. In some areas the clear cells predominated. Immunocytochemistry with anti-smooth muscle myosin produced staining of many of the clear cells (Fig. 1). The inner layer of ductal cells stained with the anticallus prekeratin (Fig. 2). Ail cells gave negative reactions to staining with the monoclonal keratin 16a (Fig. 3). Basement membranes outlining the ductal structures were stained with the anti-type
IV collagen (Fig. 4). These basement membranes often appeared to be duplicated. DlSClJSSlc9N The immunocytochemical results presented in this study correlate well with previous ultrastructural descriptions of this tumor. The inner layer of cells have been described as similar to intercalated duct cells and possesstonofilaments, desmosomes,luminal
Volume Number
59 5
Epithelial-myoepithelial
carcinoma
513
Fig. 3. Immunoenzyme staining with monoclonal antikeratin 16a, showing no staining of both cell types. (Original magnification, X300.)
Fig. 4. Immunoenzyme staining with monoclonal anti-type IV collagen showing staining of replicated basement membranes. (Original magnification, x300.)
microvilli, and some cytoplasmic vesicles7 The immunocytochemical staining observed with anticallus prekeratin would support this view, as intercalated ducts in the normal gland are positive with this antibody. However, cells of the striated and excretory ducts are also positively stained,13and therefore immtmocytochemistry would not exclude the possibility that these cells may be found in the tumor. The tumor ductal cells did not stain with the monoclonal keratin 16a, and tlherefore it is unlikely that these
cells are similar in their differentiation to basally located cells in the normal gland.13The suggestion that the ductal cells are most akin to intercalated duct cells probably arises from their relationship to the proposed myoepithelial clear cells, a relationship that exists in normal glands.17 Many of the outer clear cells were positive for smooth muscle myosin, and all clear cells were negative for both keratins, suggesting a myoepithelial rather than ductal differentiation. This is, therefore,
514
Palmer
in agreement with the ultrastructure.‘, ’ It has been shown previously that the antimyosin is a very specific label for myoepithelial cells in normal glands and that only tumor cells exhibiting considerable myoepithelial differentiation are stained.13It is possible, therefore, that the clear cells in this tumor show varying degrees of myoepithelial differentiation, so that only a proportion of them are positive for myosin. This correlates well with the suggestion that the clear cells in this tumor are similar to the clear ctll myoepithelial precursors described by Tandler in human submandibular glands.7,‘7It must be realized, however, that it is not always possible to equate cells that appear as clear cells on light microscopic sections with thosethat appear electronlucent at the ultrastructural level. Moreover, clear cells have been described asvariants of many additional cell types, in addition to myoepithelial cells, in salivary gland tumors.” A multilayered complex basal lamina at the stromal-epithelial interface has been described by Corio and co-workers,’ and this finding was substantiated with the demonstration of type IV collagen in the same location. The presence of a basal lamina has been proposed as further evidence of myoepithedial differentiation, but this cannot be considered as specific. It has been suggestedthat epithelial-myoepithelial carcinoma is a variant of pleomorphic adenoma but that it is sufficiently well defined to merit individual classification.2-5The behavior of this tumor would certainly suggest that it is a separate entity because, in comparison to pleomorphic adenoma, it is more infiltrative and destructive, has a propensity for recurrences following surgical excision, and shows a tendency toward perineural involvement and iemote metastases.2,7’B The results of the present immunocytochemical study would also confirm that this tumor is quite distinct from pleomorphic adenoma. In a similar study of pleomorphic adenoma, using the same antibodies, the outer layer of cells in the double-layered ductal structures were always negative for smooth muscle myosin.13This fact may be of some diagnostic benefit. The evidence given for the cell types involved and the particular behavior of this tumor would seemto indicate that the term epithelial-myoepithelial carcinoma is most appropriate. The precursor cells of the intercalated ducts have beenimplicated in the histogenesisof this tumor. Thus, it is proposed that they give rise to both duct and myoepithelial cells, as suggested for other salivary Alternatively, the recent hypothesis gland tumors. 19,*0 proposed by Dardick and co-workers,2“22implicating neoplasia of a complete ductal/myoepithelial unit in the histogenesis of pleomorphic adenoma, could also be applied to epithelial-myoepithelial carcinoma.
Oral Surg. May, 1985
I wish to thank Dr. B.A.
Gusterson of the Ludwig
Institute for Cancer Research,London, England, for his help with this study. REFERENCES 1. Donath K, Seifert G, Schmitz R: Zur Diagnose und Ultrastruktur des tubularen Speichelgangcarcinoms. Epithelialmyoepitheliales Schalstuckcarcinom. Virchows Arch (Pathol Anat) 356: 16-31, 1972. Corridan M: Glycogen rich clear cell adenoma of the parotid gland. J Path01 Bacterial 72: 623-626, 1956. Goldman RL, Klein HZ: Glycogen-rich adenoma of the carotid gland. Cancer 30: 749-754, 1972. ‘Feyrter,-F.: ijber das glycogenreiche retikulierte Adenom der Speicheldrusen. Z Krebsforsch 65: 446-454, 1963. Saksela E, Tarkkanen J, Wartiovaara J: Parotid clear-cell adenoma of possible myoepitheliai origin. Cancer 30: 742748, 1972. (cylindroma) of 6. Bauer WH, Fox RA: Adenomyoepithelioma palatal mucous glands. Arch Path01 39: 96-102, 1945. I. Corio RL, Sciubba JJ, Brannon RB, Batsakis JG: Epithelialmyoepithelial carcinoma of intercalated duct origin. ORAL SURC ORAL MED ORAL PATHOL 93: 280-287,
! 982
8. Chen KTK: Clear cell carcinoma of the salivary gland. Hum Pathol 14: 91-93, 1983. 9. Caselitz J. LoninE T: Soecific demonstration of actin and keratin filaments-in plekmorphic adenomas by means of immunoelectronmicroscopy. Virchows Arch (Path01 Anat) 393: 153-158, 1981. IO. Caselitz J, Loning T, Staquet MJ, Seifert 6, Thivolet J: lmmunocytochemical demonstration of filamentous structures in the parotid gland: occurrence of keratin and actin in normal and tumoral parotid gland with speciai respect to the myoepithelial cells. J Cancer Res Clin Onto! 100: 59-68, 1981. 11. Caselitz J, Osborn M, Seifert G, Weber K: Intermediate sized filament proteins (Prekeratin, vimentin, desmin) in the normal parotid gland and parotid gland tumours: immunofluorescence study. Virchows Arch (Path01 Anat) 393: 273-286, 1981. 12. Krepler R, Denk HJ, Artlieb U, Mall R: Immunocytochemistry of intermediate fiiament proteins present in pleomorphic adenomas of the human parotid gland: characterization of different cell types in the same tumor. Differentiation 21: 191-199, 1982. 13. Palmer RM, Lucas RB, Knight J, Gusterson B: Immunocytochemical identification of cell types in pleomorphic adenoma, with particular reference to myoepithelial cells. J Path01 (in press, 1985). 14. Mitchell D, Gusterson BA: Simultaneous demonstration of keratin and mucin. J Histochem Cytochem 30: 707-709, 1982. MJ, Mitchell D, Ellison M, 15. Gusterson BA, Warburton Neville AM, Rudland PS: Distribution of myoepithelial cells and basement membrane proteins in the normal breast and benign and malignant breast disease. Cancer Res 42: 47634770, 1982. 16. Gusterson BA, Warburton MJ, Mitchell D, Kraft N, Hancock WW: Invading squamous cell carcinoma can retain a basal lamina: An immunohistochemical study using a monocionai antibody. Lab Invest 51: 82-87, 1984. 17. Tandler B: Ultrastructure of the human submaxillary gland. III. Myoepithelium. Z Zellforsch 68: 852-863. 1965. 18. Seifert G. Donath K: iiber das Vorkommen SOQ.heller Zellen in Speicheldrusen-tumoren: Ultrastruktur unld Differentialdiagnose. Z Krebsforsch 91: 165-182. 1978. 19. Eversole LR: Histogenetic classification of salivary tumours. Arch Path01 92: 433-443, 1971. 20. Regezi JA, Batsakis JG: Histogenesis of salivary gland neoplasms. Otolaryngol Clin North Am 10: 297-307, 1977. 21. Dardick I, Van Norstrand AWP, Jeans MTD Rippstein P,
Epithelial-myoepithelial
Volume 59 Number 5 Edwards V: Pleomorphic adenoma. I. Ultrastructural organization of “epithelial” regions. H[um Path01 14: 780-797, 1983. 22. Dardick I, Van Norstrand AWP, Jeans MTD, Rippstein P, Edwards V: Pleomorphic adenoma. II. Ultrastructural organization of “stromal” regions. Hum Path01 14: 798809, 1983.
BOUND
VOLUMES
AVAILABLE
carcinoma
Reprint requests to: Dr. Richard M. Palmer Royal Dental Hospital Leicester Square London WC2H 7LJ, England
TO SUBSCRIBERS
Bound volumes of ORAL SURGERY, ORAL MEDICINE and ORAL PATHOLOGY are available to subscribers (only) for the 1985 issues from the Publisher, at a cost of $36.75 ($47.75 international) for Vmol.59 (January-June) and Vol. 60 (July-December). Shipping charges are included. Each bound volume contains a subject and author index and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact The C. V. Mosby Company, Circulation Department, 11830 Westline Industrial Drive, St. Louis, Missouri 63146, USA; phone (800) 325-4177, ext. 351. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular journal subscription.
515