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Lingual rhabdomyoma in a dog
J, Comp.
Path.
1992 Vol.
106, 83-87
Lingual Rachel
Rhabdomyoma
Y. Reams
Rivera
in a Dog and
W. W. Carlton
Department of Veterinary Pathobiology, Purdue University School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, U.S.A.
Summary A neutered male mixed breed dog, with a history of progressive dyspnoea, was presented for surgical removal of an enlarging lingual neoplasm (60 X 40 x 70 mm), previously diagnosed as a granular cell tumour. Microscopically the excised neoplasm comprised sheets of pleomorphic cells; large granular eosinophilic cells, multinucleated giant cells and smaller angular cells. A tentative diagnosis of rhabdomyoma was based on the light microscopic changes. This diagnosis was confirmed by the ultrastructural identification of bundles of intracytoplasmic filaments (interpreted to be myosin) within the neoplastic cells and the strong positive reaction of these cells to markers for “muscle-specific” actin (HHF35). Introduction Neoplasms of striated muscle, especially benign tumours, are unusual in domestic animals. Most rhabdomyomas in the dog, and other species, have been found in the heart (Hulland, 1990) and reports of rhabdomyomas in extracardiac locations are rare. Canine rhabdomyosarcomas and rhabdomyomas may be difficult to differentiate from other “eosinophilic granular cell” neoplasms by light microscopy only. Definitive diagnosis may require the use of transmission electron microscopy and/or immunohistochemistry. This paper describes the use of both techniques, in particular “muscle-specific” markers, in addition to light microscopy, in the diagnosis of a lingual rhabdomyoma. Case Report A neutered, male mixed breed dog, 9 years of age with a history of progressive dyspnoea during the previous 6 months, was seen at the Purdue Veterinary Teaching Hospital. The dog had two slowly enlarging masses of at least 12 months duration on the tongue. The dog exhibited stertorous breathing and had a 60 X 40 X 70 mm mass in the left side of the base of the tongue, and a 3 x 3 X 2 mm mass on the ventral surface of the rostra1 portion of the tongue. A granular cell tumour had been diagnosed from two previous biopsies of the larger mass. Materials Surgical removed
excision of the two lingual en bloc, while approximately
0021-9975/92/010083
+ 05 $03.00/d
and Methods masses was performed. The smaller mass was 50 per cent of the larger neoplasm was excised, 0
1992 Academic
Press Limited
84
FL Y. R. Rivera
and
W. W. Carlton
placed in 10 per cent buffered formalin, and processed routinely for light microscopic and ultrastructural examination. Immunohistochemistry, by methods previously described (Sandusky, Carlton and Wightman, 1987)) was performed on formalinized, paraffin wax-embedded tissues. Briefly, endogenous peroxidase activity was blocked by hydrogen peroxide in absolute methanol. Normal horse serum diluted in modified phosphate buffered saline was added to the tissues, followed by a brief incubation. Primary antibodies, anti-mouse monoclonal antibody against the ~1and y isoforms of actin and anti-mouse monoclonal antibody directed against desmin, were then added and the slides incubated. Biotinylated horse anti-mouse (secondary) antisera and 3-Amino-gavidin-biotin-peroxidase were added for a 30 min incubation. ethylcarbazole was used as an indicator and the slides were counterstained with Mayer’s haematoxylin. Anti-myosin antibodies were not used since their reactivity in animal tissues and tumours is variable (Dr G. E. Sandusky, Lilly Research Laboratories, Greenfield, Indiana, personal communication).
Results On microscopic examination the smaller mass was non-neoplastic and was composed of numerous hyperplastic gustatory glands with a mild neutrophilic infiltrate. The larger mass was a well-circumscribed neoplasm, incompletely divided into lobules by fibrous connective tissue septa that replaced normal striated muscle in the base of the tongue, causing compression with mild myodegeneration of adjacent skeletal muscle. Within the neoplasm were a few isolated myofibres and scattered areas of haemorrhage. The neoplasm comprised sheets of pleomorphic neoplastic cells. There were small round cells ( 18 pm in diameter), a few large, multi-nucleated giant cells, and small angular cells admixed with large, spherical cells with abundant, granular cytoplasm and usually central or sometimes eccentric, round nuclei with diffuse chromatin and a single small nucleolus. Most cells had marked vacuolation of the cytoplasm (Fig. 1). The cytoplasm was strongly positive with the periodic acid-Schiff reaction and with phosphotungstic acid-haematoxylin (PTAH), cytoplasm of the neoplastic cells and adjacent skeletal muscle stained diffusely blue. With PTAH, although cross-striations were visible in myofibres adjacent to, and trapped within the neoplasm, no cross-striations were identified in the neopiastic cells. However the cytoplasm contained numerous deep blue granules which were interpreted as mitochondrial staining. Based on the histological features of this tumour, oncocytoma and rhabdomyoma were considered most likely. Ultrastructurally, the neoplastic cells were round to polygonal with eccentric or central round nuclei with diffuse chromatin. Cytoplasm contained numerous groups of mitochondria, often filling the cytoplasm. Mitochondria were highly pleomorphic and contained a few amorphous intramatrical inclusions. Free ribosomes, glycogen deposits, smooth endoplasmic reticulum and Golgi bodies were present but few in number. Bundles of cytoplasmic filaments, 15 nm in diameter, were scattered throughout the cytoplasm and were interpreted as myosin filaments (Fig. 2). A few bundles contained centrally located areas of intense osmophilia. Interspersed between the filaments were numerous polysomes. No desmosomes or tight junctions were observed; however, the cells were surrounded by a distinct basal lamina.
Lingual
85
Rhabdomyoma
Fig. 1.
Lingual rhabdomyoma. Neoplastic cells are large and spherical and have marked granularity and/ or vacuolation of the cytoplasm. A multinucleated neoplastic cell is in the upper right hand cc HE x245.
Fig. 2.
Lingual rhabdomyoma. The cytosol of the neoplastic and numerous pleomorphic mitochondria. x 22 400.
Fig. 3.
Lingual rhabdomyoma. Using markers for HHF35 actin, the neoplastic cells have diffuse light gold staining of the vacuolated cytoplasm (arrowhead) with superimposed central areas of more in 0znsc reaction, especially prominent in multinucleated cells (small arrow). x 245.
cells contains
myosin
filaments
(arrow1 wad)
86
R. Y. R. Rivera
and
W. W. Carlton
With HHF35 anti-muscle actin (ENZO Biochem., Inc., New York, U.S.A.), the cytoplasm of neoplastic cells stained diffusely gold with superimposed variegated areas of intense reaction (Fig. 3). Adjacent skeletal muscle and myoepithelial cells were also diffusely positive, although skeletal muscle stained most intensely in areas of cross-striation. The neoplastic cells failed to stain with anti-desmin antibody. Normal, adjacent skeletal muscle was strongly positive, but smooth muscle in arterioles within the section stained poorly. On the basis of the morphological, ultrastructural and immunohistochemical features of this neoplasm, a diagnosis of rhabdomyoma was made. Discussion
The light microscopic appearance, most notably the marked granularity of the cytoplasm in canine laryngeal rhabdomyomas, oncocytomas and lingual “granular cell” myoblastomas (Wyand and Wolke, 1968; Giles, Montgomery and Izen, 1974; Pass, Huxtable, Cooper, Watson and Thompson 1980; Liggett, Weiss and Thomas, 1985; Meuten, Calderwood Mays, Dillman, Cooper, Valentine, Kuhajda and Pass, 1985), is similar to that of the neoplasm described in this paper, although the numerous intranuclear cytoplasmic invaginations described by some authors (Meuten et al., 1985) were not seen. Although many cytoplasmic structures can give a granular appearance to the cytoplasm with light microscopy (Ghadially, 1985), both oncocytes and myocytes contain numerous mitochondria and this probably accounts for the granular, eosinophilic cytoplasm observed in both oncocytomas and rhabdomyomas. In addition, the intracytoplasmic filaments (myosin) observed in the case described, may have contributed to the cellular granularity. Reported ultrastructural features of rhabdomyoma and rhabdomyosarcoma in man and animals include a predominant population of polygonal cells with central or eccentric nuclei and abundant cytoplasm, surrounded by a continuous or discontinuous basal lamina. Important cytoplasmic features include the presence of numerous pleomorphic mitochondria which may virtually fill the cytoplasm and bundles of cytoplasmic filaments (Erlandson, 1987; Madwell, Lund, Munn and Pino, 1988; Peter and Kluge, 1970). These bundles of cytoplasmic filaments are composed of myosin and actin and represent attempts at sarcomere formation. Well-differentiated neoplasms may contain ordered, parallel arrangements of alternating myosin and actin filaments associated with ribosomes and sometimes containing recognizable Z-disk material, while less-differentiated rhabdomyoblasts may contain only irregularly-arrayed actin and myosin filaments or myosin/ribosome complexes. Immunohistochemical markers used for the diagnosis of rhabdomyosarcoma and rhabdomyoma in man and animals, include “muscle-specific” actin (HHF35), myosin, desmin, vimentin, myoglobin and Z-protein (Erlandson, 1987; Meuten et al., 1985; Morales, Gould and Nadji, 1985; Russo, 1985). Currently, actin, desmin and myoglobin are most often utilized for differentiation of striated muscle neoplasms from other spindle cell neoplasms. In man, actin, specifically HHF35, is considered the most reliable immunohistochemi-
Lingual
87
Rhabdomyoma
cal marker for rhabdomyosarcoma (Erlandson, 1987), since embryonic rhabdomyoblasts are positive for actin before becoming positive for desmin. The delayed reactivity for desmin is related to the sequence of myofibrillogenesisin rhabdomyoblasts. Positive reactivity for desmin is usually not present until the appearance of ultrastructurally recognizable Z-disk material in the cell. In our case, no well-formed Z-disk material was observed by TEM, and this may account for the negative staining observed for desmin. Acknowledgments
Immunocytochemistry serviceswere graciously provided by Dr G. E. Sandusky, Lilly Research Laboratories, Greenfield, Indiana. References
Erlandson, R. A. (1987). The ultrastructural distinction between rhabdomyosarcoma and other undifferentiated “sarcomas”. Ultrastructural Pathology, 11, 83-107. Ghadially, F. N. ( 1985). Differential diagnosisof eosinophilic granular cell tumours. In Diagnostic Electron Microscopy of Turnours, 2nd Edit. Butterworths, London, U.K., pp. 152-l 76. Giles, R. C., Montgomery, C. A. and Izen, L. (1974). Canine lingual granular cell myoblastoma: a casereport. American Journal of Veterinav Research, 35, 1357-l 359. Hulland, T. J. (1990). Tumors of the muscle. Chapter 8. In Tumors in Domestic Animals, 3rd Edit. J. E. Moulton, Ed., University of California Press,Berkeley, California, pp. 93-95. Liggett, A. D., Weiss, L. and Thomas, K. L. (1985). Canine laryngopharyngeal rhabdomyoma resembling an oncocytoma: light microscopic, ultrastructural and comparative studies. Veterinary Pathology, 22, 526-532. Madwell, B., Lund, J., Munn, R. and Pino, M. (1988). Canine laryngeal rhabdomyosarcoma: an immunohistochemical and electron microscopic study. Japanese Journal of Veterinary Science, 50, 1079-l 084. Meuten, D. J., Calderwood Mays, M. B., Dillman, R. C., Cooper, B. J., Valentine, B. A., Kuhajda, F. P. and Pass,D. A. (1985). Canine laryngeal rhabdomyoma. Veterinary Pathology, 22, 533-539.
Morales, A. R., Gould, E. W. and Nadji, M. (1985). Immunochemistry of soft tissue tumors. In Proceedings of the Workshop on Immunocytochemistry in Tumor Diagnosis, J. Russo, Ed., Detroit, Michigan, October 3-5, 1984. Martinus Nijhoff Publishing, Boston, Massachusetts,pp. 362-379. Pass, D. C., Huxtable, C. R., Cooper, B. J., Watson, A. D. J. and Thompson, R. (1980). Canine laryngeal oncocytoma. Veterinary Pathology, 17, 672-677. Peter, C. P. and Kluge, J. P. (1970). A n ultrastructural study of a canine rhabdomysarcoma. Cancer, 26, 1280-I 288. Russo, I. H. (1985). Immunocytochemistry in tumor diagnosis. In Proceedings of the Workshop on Immunocytochemistry in Tumor Diagnosis, J. Russo, Ed., Detroit, Michigan, 3-5 October, 1984. Martinus Nijhoff Publishing, Boston, Massachusetts,p. 6. Sandusky, G. E., Carlton, W. W. and Wightman, K. A. (1987). Diagnostic immunohistochemistry of canine round cell tumors. Veterinary Pathology, 24, 495-499.
Wyand, D. S. and Wolke, R. E. ( 1968). G ranular cell myoblastoma of the canine tongue: casereports. American Journal of Veterinary Research, 29, 1309-l 3 13
1
Received, April 12th, 1991 Accepted, 34~ 24th, 1991
Path.
1992 Vol.
106, 83-87
Lingual Rachel
Rhabdomyoma
Y. Reams
Rivera
in a Dog and
W. W. Carlton
Department of Veterinary Pathobiology, Purdue University School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, U.S.A.
Summary A neutered male mixed breed dog, with a history of progressive dyspnoea, was presented for surgical removal of an enlarging lingual neoplasm (60 X 40 x 70 mm), previously diagnosed as a granular cell tumour. Microscopically the excised neoplasm comprised sheets of pleomorphic cells; large granular eosinophilic cells, multinucleated giant cells and smaller angular cells. A tentative diagnosis of rhabdomyoma was based on the light microscopic changes. This diagnosis was confirmed by the ultrastructural identification of bundles of intracytoplasmic filaments (interpreted to be myosin) within the neoplastic cells and the strong positive reaction of these cells to markers for “muscle-specific” actin (HHF35). Introduction Neoplasms of striated muscle, especially benign tumours, are unusual in domestic animals. Most rhabdomyomas in the dog, and other species, have been found in the heart (Hulland, 1990) and reports of rhabdomyomas in extracardiac locations are rare. Canine rhabdomyosarcomas and rhabdomyomas may be difficult to differentiate from other “eosinophilic granular cell” neoplasms by light microscopy only. Definitive diagnosis may require the use of transmission electron microscopy and/or immunohistochemistry. This paper describes the use of both techniques, in particular “muscle-specific” markers, in addition to light microscopy, in the diagnosis of a lingual rhabdomyoma. Case Report A neutered, male mixed breed dog, 9 years of age with a history of progressive dyspnoea during the previous 6 months, was seen at the Purdue Veterinary Teaching Hospital. The dog had two slowly enlarging masses of at least 12 months duration on the tongue. The dog exhibited stertorous breathing and had a 60 X 40 X 70 mm mass in the left side of the base of the tongue, and a 3 x 3 X 2 mm mass on the ventral surface of the rostra1 portion of the tongue. A granular cell tumour had been diagnosed from two previous biopsies of the larger mass. Materials Surgical removed
excision of the two lingual en bloc, while approximately
0021-9975/92/010083
+ 05 $03.00/d
and Methods masses was performed. The smaller mass was 50 per cent of the larger neoplasm was excised, 0
1992 Academic
Press Limited
84
FL Y. R. Rivera
and
W. W. Carlton
placed in 10 per cent buffered formalin, and processed routinely for light microscopic and ultrastructural examination. Immunohistochemistry, by methods previously described (Sandusky, Carlton and Wightman, 1987)) was performed on formalinized, paraffin wax-embedded tissues. Briefly, endogenous peroxidase activity was blocked by hydrogen peroxide in absolute methanol. Normal horse serum diluted in modified phosphate buffered saline was added to the tissues, followed by a brief incubation. Primary antibodies, anti-mouse monoclonal antibody against the ~1and y isoforms of actin and anti-mouse monoclonal antibody directed against desmin, were then added and the slides incubated. Biotinylated horse anti-mouse (secondary) antisera and 3-Amino-gavidin-biotin-peroxidase were added for a 30 min incubation. ethylcarbazole was used as an indicator and the slides were counterstained with Mayer’s haematoxylin. Anti-myosin antibodies were not used since their reactivity in animal tissues and tumours is variable (Dr G. E. Sandusky, Lilly Research Laboratories, Greenfield, Indiana, personal communication).
Results On microscopic examination the smaller mass was non-neoplastic and was composed of numerous hyperplastic gustatory glands with a mild neutrophilic infiltrate. The larger mass was a well-circumscribed neoplasm, incompletely divided into lobules by fibrous connective tissue septa that replaced normal striated muscle in the base of the tongue, causing compression with mild myodegeneration of adjacent skeletal muscle. Within the neoplasm were a few isolated myofibres and scattered areas of haemorrhage. The neoplasm comprised sheets of pleomorphic neoplastic cells. There were small round cells ( 18 pm in diameter), a few large, multi-nucleated giant cells, and small angular cells admixed with large, spherical cells with abundant, granular cytoplasm and usually central or sometimes eccentric, round nuclei with diffuse chromatin and a single small nucleolus. Most cells had marked vacuolation of the cytoplasm (Fig. 1). The cytoplasm was strongly positive with the periodic acid-Schiff reaction and with phosphotungstic acid-haematoxylin (PTAH), cytoplasm of the neoplastic cells and adjacent skeletal muscle stained diffusely blue. With PTAH, although cross-striations were visible in myofibres adjacent to, and trapped within the neoplasm, no cross-striations were identified in the neopiastic cells. However the cytoplasm contained numerous deep blue granules which were interpreted as mitochondrial staining. Based on the histological features of this tumour, oncocytoma and rhabdomyoma were considered most likely. Ultrastructurally, the neoplastic cells were round to polygonal with eccentric or central round nuclei with diffuse chromatin. Cytoplasm contained numerous groups of mitochondria, often filling the cytoplasm. Mitochondria were highly pleomorphic and contained a few amorphous intramatrical inclusions. Free ribosomes, glycogen deposits, smooth endoplasmic reticulum and Golgi bodies were present but few in number. Bundles of cytoplasmic filaments, 15 nm in diameter, were scattered throughout the cytoplasm and were interpreted as myosin filaments (Fig. 2). A few bundles contained centrally located areas of intense osmophilia. Interspersed between the filaments were numerous polysomes. No desmosomes or tight junctions were observed; however, the cells were surrounded by a distinct basal lamina.
Lingual
85
Rhabdomyoma
Fig. 1.
Lingual rhabdomyoma. Neoplastic cells are large and spherical and have marked granularity and/ or vacuolation of the cytoplasm. A multinucleated neoplastic cell is in the upper right hand cc HE x245.
Fig. 2.
Lingual rhabdomyoma. The cytosol of the neoplastic and numerous pleomorphic mitochondria. x 22 400.
Fig. 3.
Lingual rhabdomyoma. Using markers for HHF35 actin, the neoplastic cells have diffuse light gold staining of the vacuolated cytoplasm (arrowhead) with superimposed central areas of more in 0znsc reaction, especially prominent in multinucleated cells (small arrow). x 245.
cells contains
myosin
filaments
(arrow1 wad)
86
R. Y. R. Rivera
and
W. W. Carlton
With HHF35 anti-muscle actin (ENZO Biochem., Inc., New York, U.S.A.), the cytoplasm of neoplastic cells stained diffusely gold with superimposed variegated areas of intense reaction (Fig. 3). Adjacent skeletal muscle and myoepithelial cells were also diffusely positive, although skeletal muscle stained most intensely in areas of cross-striation. The neoplastic cells failed to stain with anti-desmin antibody. Normal, adjacent skeletal muscle was strongly positive, but smooth muscle in arterioles within the section stained poorly. On the basis of the morphological, ultrastructural and immunohistochemical features of this neoplasm, a diagnosis of rhabdomyoma was made. Discussion
The light microscopic appearance, most notably the marked granularity of the cytoplasm in canine laryngeal rhabdomyomas, oncocytomas and lingual “granular cell” myoblastomas (Wyand and Wolke, 1968; Giles, Montgomery and Izen, 1974; Pass, Huxtable, Cooper, Watson and Thompson 1980; Liggett, Weiss and Thomas, 1985; Meuten, Calderwood Mays, Dillman, Cooper, Valentine, Kuhajda and Pass, 1985), is similar to that of the neoplasm described in this paper, although the numerous intranuclear cytoplasmic invaginations described by some authors (Meuten et al., 1985) were not seen. Although many cytoplasmic structures can give a granular appearance to the cytoplasm with light microscopy (Ghadially, 1985), both oncocytes and myocytes contain numerous mitochondria and this probably accounts for the granular, eosinophilic cytoplasm observed in both oncocytomas and rhabdomyomas. In addition, the intracytoplasmic filaments (myosin) observed in the case described, may have contributed to the cellular granularity. Reported ultrastructural features of rhabdomyoma and rhabdomyosarcoma in man and animals include a predominant population of polygonal cells with central or eccentric nuclei and abundant cytoplasm, surrounded by a continuous or discontinuous basal lamina. Important cytoplasmic features include the presence of numerous pleomorphic mitochondria which may virtually fill the cytoplasm and bundles of cytoplasmic filaments (Erlandson, 1987; Madwell, Lund, Munn and Pino, 1988; Peter and Kluge, 1970). These bundles of cytoplasmic filaments are composed of myosin and actin and represent attempts at sarcomere formation. Well-differentiated neoplasms may contain ordered, parallel arrangements of alternating myosin and actin filaments associated with ribosomes and sometimes containing recognizable Z-disk material, while less-differentiated rhabdomyoblasts may contain only irregularly-arrayed actin and myosin filaments or myosin/ribosome complexes. Immunohistochemical markers used for the diagnosis of rhabdomyosarcoma and rhabdomyoma in man and animals, include “muscle-specific” actin (HHF35), myosin, desmin, vimentin, myoglobin and Z-protein (Erlandson, 1987; Meuten et al., 1985; Morales, Gould and Nadji, 1985; Russo, 1985). Currently, actin, desmin and myoglobin are most often utilized for differentiation of striated muscle neoplasms from other spindle cell neoplasms. In man, actin, specifically HHF35, is considered the most reliable immunohistochemi-
Lingual
87
Rhabdomyoma
cal marker for rhabdomyosarcoma (Erlandson, 1987), since embryonic rhabdomyoblasts are positive for actin before becoming positive for desmin. The delayed reactivity for desmin is related to the sequence of myofibrillogenesisin rhabdomyoblasts. Positive reactivity for desmin is usually not present until the appearance of ultrastructurally recognizable Z-disk material in the cell. In our case, no well-formed Z-disk material was observed by TEM, and this may account for the negative staining observed for desmin. Acknowledgments
Immunocytochemistry serviceswere graciously provided by Dr G. E. Sandusky, Lilly Research Laboratories, Greenfield, Indiana. References
Erlandson, R. A. (1987). The ultrastructural distinction between rhabdomyosarcoma and other undifferentiated “sarcomas”. Ultrastructural Pathology, 11, 83-107. Ghadially, F. N. ( 1985). Differential diagnosisof eosinophilic granular cell tumours. In Diagnostic Electron Microscopy of Turnours, 2nd Edit. Butterworths, London, U.K., pp. 152-l 76. Giles, R. C., Montgomery, C. A. and Izen, L. (1974). Canine lingual granular cell myoblastoma: a casereport. American Journal of Veterinav Research, 35, 1357-l 359. Hulland, T. J. (1990). Tumors of the muscle. Chapter 8. In Tumors in Domestic Animals, 3rd Edit. J. E. Moulton, Ed., University of California Press,Berkeley, California, pp. 93-95. Liggett, A. D., Weiss, L. and Thomas, K. L. (1985). Canine laryngopharyngeal rhabdomyoma resembling an oncocytoma: light microscopic, ultrastructural and comparative studies. Veterinary Pathology, 22, 526-532. Madwell, B., Lund, J., Munn, R. and Pino, M. (1988). Canine laryngeal rhabdomyosarcoma: an immunohistochemical and electron microscopic study. Japanese Journal of Veterinary Science, 50, 1079-l 084. Meuten, D. J., Calderwood Mays, M. B., Dillman, R. C., Cooper, B. J., Valentine, B. A., Kuhajda, F. P. and Pass,D. A. (1985). Canine laryngeal rhabdomyoma. Veterinary Pathology, 22, 533-539.
Morales, A. R., Gould, E. W. and Nadji, M. (1985). Immunochemistry of soft tissue tumors. In Proceedings of the Workshop on Immunocytochemistry in Tumor Diagnosis, J. Russo, Ed., Detroit, Michigan, October 3-5, 1984. Martinus Nijhoff Publishing, Boston, Massachusetts,pp. 362-379. Pass, D. C., Huxtable, C. R., Cooper, B. J., Watson, A. D. J. and Thompson, R. (1980). Canine laryngeal oncocytoma. Veterinary Pathology, 17, 672-677. Peter, C. P. and Kluge, J. P. (1970). A n ultrastructural study of a canine rhabdomysarcoma. Cancer, 26, 1280-I 288. Russo, I. H. (1985). Immunocytochemistry in tumor diagnosis. In Proceedings of the Workshop on Immunocytochemistry in Tumor Diagnosis, J. Russo, Ed., Detroit, Michigan, 3-5 October, 1984. Martinus Nijhoff Publishing, Boston, Massachusetts,p. 6. Sandusky, G. E., Carlton, W. W. and Wightman, K. A. (1987). Diagnostic immunohistochemistry of canine round cell tumors. Veterinary Pathology, 24, 495-499.
Wyand, D. S. and Wolke, R. E. ( 1968). G ranular cell myoblastoma of the canine tongue: casereports. American Journal of Veterinary Research, 29, 1309-l 3 13
1
Received, April 12th, 1991 Accepted, 34~ 24th, 1991