The term rhabdoid is used because the tumor cells resemble rhabdomyoblasts
but lack myogenic markers, and pathologic diagnosis requires familiarity with these microscopic features plus awareness that adult onset is possible.
Rhabdomyosarcoma (RMS) is a rapidly growing, malignant mesenchymal neoplasm that arises from primitive muscle cells called rhabdomyoblasts
and accounts for 15-20% of all soft tissue sarcomas.
Phosphotungstic acid haematoxylin is also useful in this scenario, as it stains the rhabdomyoblasts
a deep purple colour.
Rhabdomyosarcoma is a malignant tumor originating from rhabdomyoblasts
that is rarely reported in domestic animals or in free-living and pet birds.
Sections of tumor showed areas of large "giant" multinucleated anaplastic rhabdomyoblasts
, thus making the diagnosis of pleomorphic RMS involving the pericardium and lung pleura.
Malignant schwannomas may exhibit divergent differentiation into heterologous elements, such as epithelial, cartilaginous, bony, and adipose tissue as well as rhabdomyoblasts
(malignant triton tumor).
Admixed with this population can be a second cell type of immature rhabdomyoblasts
, (14) usually comprising a small percentage of the total tumor.
Extracellular and Connective Tissue Components Background stroma Neuropil Neuroblastoma Desmoplasia Desmoplastic small cell tumor Myxoid Liposarcoma, embryonal rhabdomyosarcoma Calcifications Neuroblastoma, synovial sarcoma, and MNST Lymphoglandular Non-Hodgkin lymphoma bodies Other elements Neuronal cells Neuroblastoma, ectomesenchymoma Rhabdomyoblasts
Rhabdomyosarcoma Cross-striations Rhabdomyosarcoma Blastema/ Nephroblastoma, pleuropulmonary epithelium blastoma Abbreviation: MNST, malignant nerve sheath tumor.
are positive for myogenin, MyoD1, and desmin, but negative for pancytokeratin.
More than a third of medulloepitheliomas contain heteroplastic elements, usually hyaline cartilage, rhabdomyoblasts
, or brainlike tissue.
are recognizable by light microscopy when they show abundant eosinophilic cytoplasm and/or cross-striations.
take on numerous appearances, including small round cells to ribbon or strap shaped to large and pleomorphic.