Which of the following marker is used to diagnose rhabdomyosarcoma?
Correct Answer: Desmin
Description: Ref: Robbins Pathologic Basis of Disease, 8th edition. Page 265Explanation:RHABDOMYOSARCOMA (RMS)Most common soft-tissue sarcoma of childhood and adolescence.Arises from mesenchymal tissues.Usually appears < 20 years of age.Most common location: Head and neck (Parameningeal) > Extremities > Genitourinary' tract.In extremities, they appear in relation to skeletal muscle.Associated with:o Neurofibromatosiso Beckwith-Wiedemann syndromeo Li-Fraumem syndromeo Fetal nlchohol syndrome.MORPHOLOGYHistologically subclassified into:o Embryonal RMS.o Alveolar RMSo Pleomorphic RMS.Rhabdomyoblasto The diagnostic cell in all typeso Contains eccentric eosinophilic granular cytoplasm rich in thick and thin filamentso May be round or elongate (tadpole or strap cells) - contain cross-striations visible by light microscopy.o Ultrastructurally, contain sarcomereso Immunohistochemically they stain with antibodies to the myogenic markers Desmin. MYOD1 and Myogenin.EMBRYONAL RHABDOMYOSARCOMAMost common type (60%).It includes the sarcoma botryoides, spindle cell and anaplastic variants.Occurs in children younger than 10 years of age.Typically arises in the nasal cavity, orbit, middle ear. prostate and paratesticular region.Commonly has parental isodisomv of chromosome 1 lpl5.5, which leads to overexpression of the imprinted IGFII gene.The sarcoma botryoides subtype develops in the walls of hollow, mucosal-lined structures, such as the nasopharynx, common bile duct, bladder and vagina.Where the tumors abut the mucosa of an organ, they form a submucosal zone of hypercellularity called the cambium layer*.Grossly, seen as soft gray infiltrative mass.The tumor cells mimic skeletal muscle at various stages of embryogenesis and consist of sheets of both round and spindled cells in a myxoid stroma, resembling "Tennis racket'.Rhabdomvoblasts with visible cross-striations may be present.ALVEOLAR RHABDOMYOSARCOMAAccounts for 20% of RMS.Develop in early to middle adolescence.Commonly arises in the deep musculature of the extremities.Histologically the tumor is traversed by a network of fibrous septae that divide the cells into clusters or aggregates resembling pulmonary alveolae.Those in the center of the aggregates are dyscohesive. while those at the periphery adhere to the septae.Cells with cross-striations are identified in about 25% of cases.Cytogenetic studies: Chromosomal translocation that fuses 2 genes:o PAX3 to the FOXOla gene. t(2,13)(q35; ql4) - Aggressive and worst prognosiso PAX7 to the FOXOla gene, t( l;13)(p36; q 14).PLEOMORPHIC RHABDOMYOSARCOMACharacterized by numerous large, mu It [nucleated, bizarre eosinophilic tumor cells.This variant is rare.Arises deep soft tissue of adults.Resemble other pleomorphic sarcomas histologically.TreatmentWide-local excision.If tumor NOT amenable to primary excision: Neoadjuvant chemotherapy followed by resection of gross residual tissue.Radiation therapy: When microscopic or gross residual disease exists after initial treatment.PrognosisFactors affecting prognosis are:o Site of origin.o Resectabilityo Presence of metastasiso Number of metastatic siteso HPE features.Favorable factorsUnfavorable factors* Embryonal variant* Alveolar variantPrimary sites:Primary sites:* Orbit* Non-parameningeal head and neck* Paratestis* Vagina* Extremity* Parameningeal
Category:
Pathology
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