Vaginal Rhabdomyosarcoma in a Dog

Abstract

Abstract.A 10-year-old, female, mongrel showed hemorrhage from vulva. By magnetic resonance image (MRI) and endoscopic examination, a multipapillary mass with a grape-like appearance was found around the urethral opening. Histologically, the mass consisted of variable-sized round-, spindleto-polygonal-shaped tumor cells including many multinuclear cells. Mitotic figures were also frequently observed. In some areas, that tumor cells were loosely arranged, with intercellular myxoid components. Immunohistochemically, these tumor cells were strongly positive for vimentin and focally positive for desmin but negative for myoglobin. Thus, the case was diagnosed as a relatively poorly differentiated botryoid rhabdomyosarcoma by the macroscopic, histopathologic, and immunohistochemical identification. This is the first report of botryoid rhabdomyosarcoma developing in the vagina of a dog.Key words: Dogs; histopathology; rhabdomyosarcoma; vagina.Rhabdomyosarcoma is a malignant tumor of striated muscles, and it rarely occurs in domestic animals. On the basis of histologic features, rhabdomyosarcomas are classified into four categories: embryonal, botryoid, alveolar, and pleomorphic.3 Of these subtypes, botryoid rhabdomyosarcoma has been regarded as a variant of embryonal rhabdomyosarcoma and is characterized by polypoid, grape-like growth pattern. It has been reported to occur most commonly in the urinary bladder of large-breed dogs aged less than 2 years and has also been reported to occur in the urinary bladder of a smallbreed dog (Maltese) and a horse. 7,9 There is only one report of its occurrence in an organ other than the urinary bladder, i.e., in the uterus of a horse. 8In this article, we describe the histopathology of botryoid rhabdomyosarcoma of the vagina in dogs. To our knowledge, this is the first report of a botryoid rhabdomyosarcoma observed in an organ other than the urinary bladder in dogs.We report the case of a 10-year-old, spayed female mongrel who had continuous hemorrhaging from the vulva. The dog was referred to a veterinary hospital; endometritis was diagnosed, and the dog was ovariectomized. However, the hemorrhage did not stop, and a mass was found at the vestibulum vaginae. This mass was removed and diagnosed as a malignant tumor of unknown origin. A few months later, recurrence was observed at the same site, and hemorrhage was observed again. The dog was brought to the Animal Medical Center, College of Bioresource Sciences, Nihon University. Endoscopy revealed a grape-like, multipapillary mass (approximately 1-3 cm in diameter) around the urethral opening (Fig. 1). This mass was fragile and hemorrhaged easily, and the urethral opening was difficult to find. Magnetic resonance imagining (MRI) revealed that the urethra had translocated, and the mass had developed invasively but had a relatively clear border between it and the neighboring tissues. This mass was surgically removed, and recurrence and metastasis were not observed after this operation.The tissue samples were fixed in 10% neutral buffe...

Hematogenous metastasis of embryonal rhabdomyosarcoma originating from skeletal muscle in a young dog

“…Similar to humans, the majority of rhabdomyosarcomas reported in dogs have occurred in tissues that normally do not contain striated-muscle cells, such as the pharynx, gingiva, urethra, trachea, larynx, and the jaw bone. 6,12,14 The reason that rhabdomyosarcomas arise in these sites is not clearly understood, but it is thought that myogenic transformation may be induced in non-muscle cells by a genetic problem, such as genetic lesions, related loss of heterozygosity, genetic fusions, or tumorigenic influences. 13 In the present case, the tumor occurred in the axillary region and involved striated muscles of the shoulder and thoracic limb.…”

Aggressive Spindle Cell Rhabdomyosarcoma in an 11-Month-Old Boxer Dog

“…RMS is a tumor derived from skeletal muscle, composed of anaplastic muscle cells, and is one of the malignant neoplasms seen in veterinary medicine. According to the literature, the disease rarely affects domestic animals [8,17]. In dogs, the skeletal muscle of the tongue, larynx, myocardium and urinary bladder are the most common sites involved [2,10].…”

“…According to the animal's owner, the lesion showed a rapid growth be corresponded to its invasive pattern. Once again, just few cases of RMS have been reported in dogs and the clinical behavior in each subtype is not well understood [8,17]. Besides, its poor prognosis may be also associated to the location of the tumor, which affected the central nervous system resulting in clinical disturbances.…”

Alveolar rhabdomyosarcoma in a dog confirmed using myogenin immunohistochemistry: a case report

“…The immunohistochemical markers of skeletal muscle such as vimentin, desmin, myoglobin and myogenin play a critical role in differential diagnosis of rhabdomyosarcoma (Dias et al 2000;Suzuki et al 2006). To the authors' knowledge, in dogs, four cases of alveolar rhabdomyosarcoma (Seibold Sarnelli et al 1994;Kim et al 1996;Bae et al 2007) have been reported, which occurred in the gingiva, urinary bladder, genital tract, retroperitoneal cavity, left maxillary area and greater omentum, and these cases were confirmed via myoglobin immunohistochemistry.…”