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Pleomorphic rhabdomyosarcoma in adults: immunohistochemistry as a tool for its diagnosis
Abstract:
Pleomorphic rhabdomyosarcoma in adults over 30 years of age was a diagnosis frequently made in the 1960s and 1970s. Since the general acceptance of malignant fibrous histiocytoma (MFH) as a tumor entity at the end of the 1970s, however, it has become a very rare tumor in adults. Therefore, 21 cases originally diagnosed on the basis of histology and clinical data as pleomorphic rhabdomyosarcoma in the 1960s and 1970s were reexamined immunohistochemically. Other types of pleomorphic sarcomas involved in the differential diagnosis were also studied. Specific antibodies against vimentin, desmin, creatine kinase subunit M, skeletal muscle actin and myosin, and myoglobin, and the avidin-biotin-peroxidase complex technique were used. The immunohistochemical findings indicate that rhabdomyosarcoma occurs only rarely in adults over 30 years of age and that the majority of the tumors have to be reclassified as MFH or leiomyosarcoma. On the other hand, several pleomorphic sarcomas were found to be diagnosed incorrectly as MFH or liposarcoma by routine histologic stains and electron microscopy. The revised diagnosis was pleomorphic rhabdomyosarcoma for one case and pleomorphic leiomyosarcoma for the other cases. Thus, this study clearly shows the usefulness of immunohistochemistry as a technique in the diagnosis of pleomorphic sarcomas in adults.
Insights
Pleomorphic rhabdomyosarcoma is rare in adults over 30. Immunohistochemistry reclassified most historical cases as malignant fibrous histiocytoma (MFH) or leiomyosarcoma, highlighting diagnostic challenges.
Area of Science:
- Oncology
- Pathology
- Immunohistochemistry
Background:
- Pleomorphic rhabdomyosarcoma was frequently diagnosed in adults over 30 in the mid-20th century.
- The acceptance of malignant fibrous histiocytoma (MFH) as a distinct entity reduced the incidence of pleomorphic rhabdomyosarcoma diagnoses.
Purpose of the Study:
- To re-evaluate historical diagnoses of pleomorphic rhabdomyosarcoma in adults using immunohistochemistry.
- To clarify the diagnostic accuracy of histology and electron microscopy for pleomorphic sarcomas.
Main Methods:
- Re-examination of 21 historical pleomorphic rhabdomyosarcoma cases using immunohistochemistry.
- Utilized antibodies against vimentin, desmin, creatine kinase subunit M, skeletal muscle actin/myosin, and myoglobin.
- Employed the avidin-biotin-peroxidase complex technique.
Main Results:
- Immunohistochemistry revealed that most adult pleomorphic rhabdomyosarcomas are rare, with many reclassified as MFH or leiomyosarcoma.
- Routine histology and electron microscopy led to misdiagnosis of some pleomorphic sarcomas as MFH or liposarcoma.
- One case was reclassified as pleomorphic rhabdomyosarcoma, and others as pleomorphic leiomyosarcoma.
Conclusions:
- Immunohistochemistry is crucial for accurate diagnosis of pleomorphic sarcomas in adults.
- Historical diagnoses of pleomorphic rhabdomyosarcoma in adults require re-evaluation.
- Distinguishing between pleomorphic sarcomas like rhabdomyosarcoma, MFH, and leiomyosarcoma benefits from advanced techniques.