Tumors of Muscle

Aggressive, Solid Variant of Alveolar Rhabdomyosarcoma with Cutaneous Involvement in a Juvenile Labrador Retriever

“…ARMS cells usually express skeletal muscle markers, such as desmin, MyoD1 and myogenin, and as mesenchymal cells, they also express vimentin (Sarnelli et al, 1994;Kim et al, 1996;Cooper and Valentine, 2002;Bae et al, 2007;Murakami et al, 2010;Snyder and Michael, 2011;Boeloni et al, 2012;Kimura et al, 2013), as in our case. However, in undifferentiated or poorly differentiated rhabdomyosarcomas, desmin expression may be weak or absent (Carter et al, 1989;Cooper and Valentine, 2002;Murakami et al, 2010). Mature striated muscles do not express smooth muscle markers, but they can be observed in myoblasts during the early stage of muscle development (Kimura et al, 2013).…”

“…In man, ARMS is highly aggressive, prone to metastasis and carries a poor prognosis, occurring predominantly in adolescents, with a predilection for the extremities, paraspinal and perineal regions and the paranasal sinuses (Parham and Barr, 2002). Until now, only nine cases of ARMS have been documented in dogs aged 7 months to 10 years, with a predilection for the gingiva, subcutaneous maxillary area, uterus, ovary and omentum (Seibold, 1974;Sarnelli et al, 1994;Kim et al, 1996;Cooper and Valentine, 2002;Bae et al, 2007;Murakami et al, 2010;Snyder and Michael, 2011;Boeloni et al, 2012;Kimura et al, 2013). Distant metastasis to the brain, lung and abdominal viscera was observed in only four of the cases.…”

“…ARMS, generally included in the group of round cell tumours, arises from poorly differentiated skeletal muscle precursor cells (Cooper and Valentine, 2002;Parham and Barr, 2002;Caserto, 2013). In the case of the classic ARMS subtype with distinct fibrovascular septa, the morphological diagnosis is not difficult, but in the case of the solid variant, especially when the lesions are observed in unusual places, diagnosis may be problematic (Caserto, 2013).…”

“…The three major histological subtypes of ARMS are: the classic alveolar type, composed of small round cells with scant cytoplasm and arranged in packets delineated by fibrous connective tissue septa; the solid variant, characterized by sheets of small round cells closely packed together with no or minimal fibrovascular stroma, resembling a 'neuroendocrine pattern'; and the mixed embryonal/alveolar form, comprising of myogenic cells in different stages of differentiation with myxoid stroma and areas with a typical alveolar pattern (Cooper and Valentine, 2002;Parham and Barr, 2002;Caserto, 2013). In man, ARMS is highly aggressive, prone to metastasis and carries a poor prognosis, occurring predominantly in adolescents, with a predilection for the extremities, paraspinal and perineal regions and the paranasal sinuses (Parham and Barr, 2002).…”

“…Alveolar rhabdomyosarcoma (ARMS) is a rare, malignant round cell tumour, reminiscent of lymphoma and originating from poorly differentiated myogenic precursor cells (Cooper and Valentine, 2002;Parham and Barr, 2002;Caserto, 2013). The three major histological subtypes of ARMS are: the classic alveolar type, composed of small round cells with scant cytoplasm and arranged in packets delineated by fibrous connective tissue septa; the solid variant, characterized by sheets of small round cells closely packed together with no or minimal fibrovascular stroma, resembling a 'neuroendocrine pattern'; and the mixed embryonal/alveolar form, comprising of myogenic cells in different stages of differentiation with myxoid stroma and areas with a typical alveolar pattern (Cooper and Valentine, 2002;Parham and Barr, 2002;Caserto, 2013).…”