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Rhabdomyoma of the ear pinna in four cats
j. Comp. Path. 1990 Vol. 103
Rhabdomyoma
o f the Ear P i n n a in F o u r Cats Lois R o t h
Department of Comparative and Experimental P~lhology, Collegeof VeterinaryMedicine, Box J-145, J. Hillis Miller Health Center, Universilyof Florida, Gainesville, Florida 32610, U.S.A.
Summary Four cases of rhabdomyoma of the ear pinna in white eared adult cats are reported. The lesions were raised, non-ulcerated, red-purple, discoid nodules on the convex surface of the pinna. Histologically, the nodules consisted of interlacing bundles of spindle-shaped ceils that occasionally had cross striations. Lesions have not recurred 2-3 years following surgical excision. Although a specific cause for tumour development was not found, the similarity among these cases suggests that common factors played a role in the development of the lesions.
Introduction R h a b d o m y o m a s , benign tumours of striated muscle, occur infrequently in all species of domestic animals at any anatomical site (Worley and Gorham, 1954; Brodey, 1970; Hulland, 1978). The most common reports of rhabdomyoma include those located in the urinary bladder, lung and kidney (Worley and G o r h a m , 1954; Hulland, 1978). The following case report describes the occurrence of r h a b d o m y o m a s on the white-haired ear pinnas of four domestic shorthair cats.
Case Report Tissue from all four cases, which included portions of the ear pinna and associated mass lesions, was submitted in formalin by veterinary clinicians. The clinical diagnosis in all cases was squamous cell carcinoma. Three of the affected cats were 6 years old and the fourth 7 years old. T w o were female and two were spayed female cats. Three of the cats were completely white. The fourth cat was white and grey, the affected pinna being completely white. The cats were from scattered locations in the eastern United States. Two cats were feline leukaemia virus-negative as assessed by the ELISA test. The feline leukaemia virus status of the other two was unknown.
Gross and Histopathology All lesions appeared similar. They were thinly haired, reddish-purple, nonulcerated discoid masses ranging from 1.0 to 2"0 cm in diameter and protrud0021-9975/90/060237 + 04 g03.00/0
© 1990 Academic Press Limited
238
Lois Roth
Fig. l.
Low magnification of a typical rhabdomyoma of the ear pinna. Although not encapsulated, the tumour margins (arrows) are distinct. The underlying cartilage is not deforrned. HE x 32.
Fig. 2.
Higher magnification of a rhabdomyoma of the ear pinna. It is characterized by plump, spindleshaped cells, arranged in bundles. HE x 300.
Fig. 3.
Cross striations are observed in occasional neoplastic cells. PTAH x 750.
Rhabdomyoma of Feline Ear
239
ing 0"25 to 0'5 cm from the convex surface of the pinna. Histologically, the I lesions were well circumscribed, no'n-encapsulated nodules within the dermis causing focal elevation of the epidermis, but not deforming the underlying cartilage of the pinna (Fig. 1). T h e nodules consisted of whorls and bundles of elongated spindle-shaped cells (Fig. 2). Mitotic figures were rarely observed. In all cases, neoplastic cells stained intensely red with Masson's trichrome stain, indicating that the cells were muscle cells. In control tissues, muscle fibres also stained red, while fibrocytes stained green. Phosphotungstic acid haematoxylin (PTAH) staining enhanced the appearance of cross striations in a few scattered neoplastic cells (Fig. 3). In all four cases, complete surgical excision of the initial lesion effected a cure. Regrowth of the neoplasms has not occurred during the following 2 to 3 years.
Discussion
The ear pinna is a relatively uncommon site for neoplasms (Hulland, 1978; Angarano, 1988). Squamous cell carcinoma is the most frequently occurring tumour affecting the ear pinna, particularly in white cats (Angarano, 1988). These neoplasms usually involve the distal pinna, appear as irregular, crusty, often ulcerated, proliferative lesions and are considered to be sunlight induced (Angarano, 1988). It is interesting that all four cases of rhabdomyoma reported here involved white-haired ear pinna. R h a b d o m y o m a s of the ear pinna have not been reported (Brodey, 1970; Hulland, 1978; Angarano, 1988). Although a cause and effect relationship with traumatic muscle damage and the development of rhabdomyoma has been suggested (Hulland, 1978), this cannot be substantiated in the cases described here. Muscle implants of nickel sulphide have been used to induce experimental rhabdomyomas in rats and it is suggested that nickel compounds present in the environment play a role in the development of these neoplasms (Corbeil, 1968). The sporadic occurrence of rhabdomyoma and differing geographical origins of the four cats discussed here suggests that other factors play a role in the development of this neoplasm. Viruses, particularly feline sarcoma virus and feline leukaemia virus, have been associated with the development of mesenchymal tumours in cats (Essex, Klein, Snyder and Harrold, 1971 ; Cotter, Hardy and Essex, 1975). Rhabdomyomas are not included among the tumours associated with these agents. Although two of the cats were serologically negative for feline leukaemia virus, serological titres for feline sarcoma virus on all four cats and feline leukaemia virus for the two other cats could not be obtained. T h e factors that influenced the development of this relatively uncommon t u m o u r in these cats are unknown. The strong similarities among these cases, however, suggests that common factors are involved. References
Angarano, D. W. (1988). Diseases of the pinna. Veterinary Clinics of North America-Small Animal Practice, 18, 869-884.
240
Lois Roth
Brodey, R. S. (1970). Canine and feline neoplasia. Advances in Veterinary Science and Comparative Medicine, 14, 309-354. Corbeil, L. B. (1968). Antigenicity of rhabdomyosarcoma induced by nickel sulfide (Ni3S2). Cancer, 21, 184-189. Cotter, S. M., Hardy, W. D. Jr and Essex, M. (1975). Association of feline leukemia virus and lymphosarcoma with other disorders of the cat. Journal of the American Veterinary Medical Association, 166, 449-454. Essex, M., Klein, G., Snyder, S. P. and Harrold, J. B. (1971). Correlation between humoral antibody and regression of tumors induced by feline sarcoma virus. Nature, 233, 195-196. Hulland, T.J. (1978), Tumors of muscle. In Tumors in Domestic Animals, 2nd edit., J. E. Mouhon, Ed. University of California Press, Berkeley, CA, pp. 75-88. Worley, G. and Gorham, J. R. (1954). The comparative pathology of"rhabdomyosarcoma with the report of a case. American Journal of Pathology, 30, 837-849.
I Received, September 27th, 1989 Accepted, November 22nd, 1989J
Rhabdomyoma
o f the Ear P i n n a in F o u r Cats Lois R o t h
Department of Comparative and Experimental P~lhology, Collegeof VeterinaryMedicine, Box J-145, J. Hillis Miller Health Center, Universilyof Florida, Gainesville, Florida 32610, U.S.A.
Summary Four cases of rhabdomyoma of the ear pinna in white eared adult cats are reported. The lesions were raised, non-ulcerated, red-purple, discoid nodules on the convex surface of the pinna. Histologically, the nodules consisted of interlacing bundles of spindle-shaped ceils that occasionally had cross striations. Lesions have not recurred 2-3 years following surgical excision. Although a specific cause for tumour development was not found, the similarity among these cases suggests that common factors played a role in the development of the lesions.
Introduction R h a b d o m y o m a s , benign tumours of striated muscle, occur infrequently in all species of domestic animals at any anatomical site (Worley and Gorham, 1954; Brodey, 1970; Hulland, 1978). The most common reports of rhabdomyoma include those located in the urinary bladder, lung and kidney (Worley and G o r h a m , 1954; Hulland, 1978). The following case report describes the occurrence of r h a b d o m y o m a s on the white-haired ear pinnas of four domestic shorthair cats.
Case Report Tissue from all four cases, which included portions of the ear pinna and associated mass lesions, was submitted in formalin by veterinary clinicians. The clinical diagnosis in all cases was squamous cell carcinoma. Three of the affected cats were 6 years old and the fourth 7 years old. T w o were female and two were spayed female cats. Three of the cats were completely white. The fourth cat was white and grey, the affected pinna being completely white. The cats were from scattered locations in the eastern United States. Two cats were feline leukaemia virus-negative as assessed by the ELISA test. The feline leukaemia virus status of the other two was unknown.
Gross and Histopathology All lesions appeared similar. They were thinly haired, reddish-purple, nonulcerated discoid masses ranging from 1.0 to 2"0 cm in diameter and protrud0021-9975/90/060237 + 04 g03.00/0
© 1990 Academic Press Limited
238
Lois Roth
Fig. l.
Low magnification of a typical rhabdomyoma of the ear pinna. Although not encapsulated, the tumour margins (arrows) are distinct. The underlying cartilage is not deforrned. HE x 32.
Fig. 2.
Higher magnification of a rhabdomyoma of the ear pinna. It is characterized by plump, spindleshaped cells, arranged in bundles. HE x 300.
Fig. 3.
Cross striations are observed in occasional neoplastic cells. PTAH x 750.
Rhabdomyoma of Feline Ear
239
ing 0"25 to 0'5 cm from the convex surface of the pinna. Histologically, the I lesions were well circumscribed, no'n-encapsulated nodules within the dermis causing focal elevation of the epidermis, but not deforming the underlying cartilage of the pinna (Fig. 1). T h e nodules consisted of whorls and bundles of elongated spindle-shaped cells (Fig. 2). Mitotic figures were rarely observed. In all cases, neoplastic cells stained intensely red with Masson's trichrome stain, indicating that the cells were muscle cells. In control tissues, muscle fibres also stained red, while fibrocytes stained green. Phosphotungstic acid haematoxylin (PTAH) staining enhanced the appearance of cross striations in a few scattered neoplastic cells (Fig. 3). In all four cases, complete surgical excision of the initial lesion effected a cure. Regrowth of the neoplasms has not occurred during the following 2 to 3 years.
Discussion
The ear pinna is a relatively uncommon site for neoplasms (Hulland, 1978; Angarano, 1988). Squamous cell carcinoma is the most frequently occurring tumour affecting the ear pinna, particularly in white cats (Angarano, 1988). These neoplasms usually involve the distal pinna, appear as irregular, crusty, often ulcerated, proliferative lesions and are considered to be sunlight induced (Angarano, 1988). It is interesting that all four cases of rhabdomyoma reported here involved white-haired ear pinna. R h a b d o m y o m a s of the ear pinna have not been reported (Brodey, 1970; Hulland, 1978; Angarano, 1988). Although a cause and effect relationship with traumatic muscle damage and the development of rhabdomyoma has been suggested (Hulland, 1978), this cannot be substantiated in the cases described here. Muscle implants of nickel sulphide have been used to induce experimental rhabdomyomas in rats and it is suggested that nickel compounds present in the environment play a role in the development of these neoplasms (Corbeil, 1968). The sporadic occurrence of rhabdomyoma and differing geographical origins of the four cats discussed here suggests that other factors play a role in the development of this neoplasm. Viruses, particularly feline sarcoma virus and feline leukaemia virus, have been associated with the development of mesenchymal tumours in cats (Essex, Klein, Snyder and Harrold, 1971 ; Cotter, Hardy and Essex, 1975). Rhabdomyomas are not included among the tumours associated with these agents. Although two of the cats were serologically negative for feline leukaemia virus, serological titres for feline sarcoma virus on all four cats and feline leukaemia virus for the two other cats could not be obtained. T h e factors that influenced the development of this relatively uncommon t u m o u r in these cats are unknown. The strong similarities among these cases, however, suggests that common factors are involved. References
Angarano, D. W. (1988). Diseases of the pinna. Veterinary Clinics of North America-Small Animal Practice, 18, 869-884.
240
Lois Roth
Brodey, R. S. (1970). Canine and feline neoplasia. Advances in Veterinary Science and Comparative Medicine, 14, 309-354. Corbeil, L. B. (1968). Antigenicity of rhabdomyosarcoma induced by nickel sulfide (Ni3S2). Cancer, 21, 184-189. Cotter, S. M., Hardy, W. D. Jr and Essex, M. (1975). Association of feline leukemia virus and lymphosarcoma with other disorders of the cat. Journal of the American Veterinary Medical Association, 166, 449-454. Essex, M., Klein, G., Snyder, S. P. and Harrold, J. B. (1971). Correlation between humoral antibody and regression of tumors induced by feline sarcoma virus. Nature, 233, 195-196. Hulland, T.J. (1978), Tumors of muscle. In Tumors in Domestic Animals, 2nd edit., J. E. Mouhon, Ed. University of California Press, Berkeley, CA, pp. 75-88. Worley, G. and Gorham, J. R. (1954). The comparative pathology of"rhabdomyosarcoma with the report of a case. American Journal of Pathology, 30, 837-849.
I Received, September 27th, 1989 Accepted, November 22nd, 1989J