Ewing sarcoma with myxoid stroma: Case report of an unusual histological variant

We describe the case of a Ewing sarcoma with prominent myxoid stroma of the temporal bone in a 26-year-old female. Histologically, the tumor exhibited a fascicular growth pattern of round to spindled cells with a minimal amount of pale eosinophilic to clear cytoplasm and oval or spindled nuclei with...

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Bibliographic Details
Published in:Pathology, research and practice research and practice, 2019-12, Vol.215 (12), p.152665, Article 152665
Main Authors: Alexiev, Borislav A., Obeidin, Farres, Jennings, Lawrence J.
Format: Article
Language:English
Subjects:
12E7 Antigen - analysis
Adult
Biomarkers, Tumor - analysis
Biomarkers, Tumor - genetics
Bone Neoplasms - chemistry
Bone Neoplasms - genetics
Bone Neoplasms - pathology
Bone Neoplasms - therapy
CD56 Antigen - analysis
Diagnosis, Differential
Ewing sarcoma
EWSR1-FLI1 fusion transcript
Female
Gene Fusion
Humans
Myxoid variant
Oncogene Proteins, Fusion - genetics
Predictive Value of Tests
Sarcoma, Ewing - chemistry
Sarcoma, Ewing - genetics
Sarcoma, Ewing - pathology
Sarcoma, Ewing - therapy
Stromal Cells - chemistry
Stromal Cells - pathology
Temporal Bone - chemistry
Temporal Bone - pathology
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Summary:We describe the case of a Ewing sarcoma with prominent myxoid stroma of the temporal bone in a 26-year-old female. Histologically, the tumor exhibited a fascicular growth pattern of round to spindled cells with a minimal amount of pale eosinophilic to clear cytoplasm and oval or spindled nuclei with finely dispersed chromatin and small nucleoli. Myxoid changes were prominent (>50%), with reticular or pseudoacinar growth of the loosely cohesive cells. The tumor showed strong expression of CD99, FLI1, and CD56 and was positive for the EWSR1-FLI1 fusion transcript. The diagnosis of Ewing sarcoma with myxoid stroma (myxoid variant) is particularly problematic owing to the large number of potential mimics. The tumor extends the morphologic spectrum of Ewing sarcoma beyond the previously described histological variants, and broadens the differential diagnosis. For any round/spindle cell sarcoma, prominent myxoid stroma and CD99 immunoreactivity should prompt consideration for molecular studies that include analysis of both EWSR1 and FLI1.
ISSN:0344-0338
1618-0631
DOI:10.1016/j.prp.2019.152665