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Rhabdomyosarcoma in middle-aged and elderly individuals
T Seidal1, L G Kindblom, L Angervall
1Department of Pathology, University of Gothenburg, Sahlgren Hospital, Sweden.
Summary
This study investigated rhabdomyosarcomas in older adults, finding that pleomorphic rhabdomyosarcomas are rare or nonexistent. Immunohistochemistry confirmed rhabdomyoblastic differentiation in most cases, aiding diagnosis.
Area of Science:
- Oncology
- Pathology
- Cancer Research
Background:
- Rhabdomyosarcoma is rare in adults over 40.
- Accurate diagnosis relies on distinguishing subtypes.
Purpose of the Study:
- To investigate the occurrence and characteristics of rhabdomyosarcomas in middle-aged and elderly individuals.
- To evaluate the diagnostic utility of electron microscopy and immunohistochemistry for rhabdomyosarcoma subtypes.
Main Methods:
- Review of 107 Swedish Cancer Registry cases diagnosed as rhabdomyosarcoma (1972-1981).
- Electron microscopy and immunohistochemical analysis (desmin, myoglobin, vimentin, actin) on 11 rhabdomyosarcoma cases.
- Analysis of 9 pleomorphic sarcomas for myogenic differentiation.
Main Results:
- Rhabdomyoblastic differentiation confirmed ultrastructurally in 10/11 cases.
- Desmin and actin were positive in all cases; myoglobin in 7/11; vimentin in 5/11.
- A novel 'epithelioid rhabdomyosarcoma' subtype was identified.
- No myogenic differentiation found in 9 pleomorphic sarcomas, suggesting they are not true rhabdomyosarcomas.
Conclusions:
- Pleomorphic rhabdomyosarcoma is extremely rare or non-existent in adults.
- Immunohistochemistry, particularly desmin staining, is valuable for diagnosing rhabdomyosarcoma in formaldehyde-fixed, paraffin-embedded tissues.
- Further investigation is needed for the newly proposed 'epithelioid rhabdomyosarcoma' entity.