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Primitive rhabdomyosarcoma presenting with diffuse bone marrow involvement: an immunohistochemical and
K R Cho1, J L Olson, J I Epstein
1Johns Hopkins Hospital, Department of Pathology, Baltimore, Maryland.
Summary
Primitive rhabdomyosarcoma (PRMS) can mimic acute leukemia when presenting with bone marrow infiltration. Recognizing subtle ultrastructural findings is crucial for accurate diagnosis, as immunohistochemistry can be inconclusive.
Area of Science:
- Oncology
- Pathology
- Pediatric Cancer
Background:
- Primitive rhabdomyosarcoma (PRMS) is a rare soft tissue sarcoma.
- PRMS typically presents as a palpable mass.
- Diagnosis relies on characteristic histology and immunohistochemistry.
Observation:
- Three cases of PRMS presented with diffuse bone marrow infiltration.
- Soft tissue primaries were inconspicuous in these cases.
- Patients were initially referred with suspected acute leukemia.
Findings:
- Immunohistochemical staining and electron microscopy confirmed PRMS.
- Ultrastructural analysis revealed thin filaments, discontinuous basal lamina, glycogen, and primitive cell junctions.
- Muscle-specific markers were not always definitively positive, highlighting diagnostic challenges.
Implications:
- PRMS with bone marrow infiltration may be underdiagnosed.
- Distinguishing PRMS from hematopoietic tumors requires careful evaluation.
- Electron microscopy is essential when immunohistochemistry is equivocal for PRMS diagnosis.