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

Abstract

ABSTRACT. Rhabdomyosarcoma (RMS) is a malignant neoplasm derived from mesenchymal tissue with a tendency toward myogenic differentiation associated with the embryogenesis of skeletal muscle. According to the histological features, it can be classified in embryonal, botryoid, alveolar, and pleomorphic, which usually correspond to clinical behavior and prognosis. The spindle cell (SCRMS) variant is a rare subtype of the embryonal RMS and is considered to be less aggressive lesion. The aim of the present paper is to report an unusual case of SCRMS in an 11-month-old male boxer dog diagnosed as extensive SCRMS that affected the frontal region of the skull. Due to the aggressive nature of the lesion and poor clinical prognosis the dog's owners preferred euthanasia as a treatment. A full postmortem examination was carried out. Microscopically, the lesion was composed of a highly cellular proliferation of spindle cells arranged in long and intersecting fascicles. After performing the immunohistochemical studies (HHF-35, smooth muscle actin, desmin and MyoD1), the present case was diagnosed as SCRMS.

A Comparative Review of Canine and Human Rhabdomyosarcoma With Emphasis on Classification and Pathogenesis

“…Embryonal RMS includes 3 variants that are named because of their predominant cellular morphology. 31,35,36,109 The myotubular variant of embryonal RMS is dominated by multinucleated "strap" cells forming myotubes with frequent cross-striations (often only identified by histochemical staining with phosphotungstic acid hematoxylin [PTAH] stain, which highlights striations as dark blue/purple lines among paler blue/purple myofibers), whereas the rhabdomyoblastic variant is dominated by round to polygonal cells with abundant eosinophilic cytoplasm (Fig. 2), with only rare PTAH positive cross-striations.…”

“…This mass was composed of interlacing fascicles of plump spindle cells. 35 The spindyloid embryonal RMS, as the name implies, is composed of thin spindyloid myoblast cells forming bundles within a myxoid stroma. Although limited case reports exist, these neoplasms in humans typically have a better prognosis than any other variant of RMS.…”

Biological behaviour and ezrin expression in canine rhabdomyosarcomas: 25 cases (1990‐2012)

“…Rhabdomyosarcomas (RMS) are soft tissue sarcomas (STS) that arise from primitive mesenchymal cells and show varying degrees of skeletal muscle differentiation 1,2 . RMS are rare tumours in dogs with only a limited number of cases reported in the literature; however, they appear to occur more commonly in young dogs 3‐11 . Recently, a predilection for the retrobulbar space has been described; in dogs younger than 4 years of age, this disease appears to exhibit a particularly aggressive clinical course with a very short survival time 12 .…”

Oral pleomorphic rhabdomyosarcoma in a dog with the lung metastasis

“…Rhabdomyosarcoma (RMS) is a type of sarcomas made up of cells that normally develop into skeletal muscles (1,9,13). Althought several reports about canine rhabdomyosarcoma have been published especially on cardiac, laryngeal and urogenital forms (3,7,8,10,13,15) and also oral tumors have been moderately common observed in dogs (5), the oral cavity tumors of rhabdomyosarcoma has been quite limited (4,9,11,12). There are several types of rhabdomyosarcoma.…”

“…This uncommon cancer tends to grow quickly and usually require intensive treatment. The prognosis are poor most of the time (1,13).…”