J Pathol Transl Med.  2024 Sep;58(5):255-260. 10.4132/jptm.2024.08.15.

Rhabdomyosarcoma of the skull with EWSR1 fusion and ALK and cytokeratin expression: a case report

• An HR
• Cho KJ
• Song SW
• Park JE
• Song JS

• KMID: 2559071
• DOI: http://doi.org/10.4132/jptm.2024.08.15

Abstract

Rhabdomyosarcoma (RMS) comprises of heterogeneous group of neoplasms that occasionally express epithelial markers on immunohistochemistry (IHC). We herein report the case of a patient who developed RMS of the skull with EWSR1 fusion and anaplastic lymphoma kinase (ALK) and cytokeratin expression as cytomorphologic features. A 40-year-old man presented with a mass in his forehead. Surgical resection was performed, during which intraoperative frozen specimens were obtained. Squash cytology showed scattered or clustered spindle and epithelioid cells. IHC revealed that the resected tumor cells were positive for desmin, MyoD1, cytokeratin AE1/ AE3, and ALK. Although EWSR1 rearrangement was identified on fluorescence in situ hybridization, ALK, and TFCP2 rearrangement were not noted. Despite providing adjuvant chemoradiation therapy, the patient died of tumor progression 10 months after diagnosis. We emphasize that a subset of RMS can express cytokeratin and show characteristic histomorphology, implying the need for specific molecular examination.

Keyword

Rhabdomyosarcoma; Skull; protein; Keratins; Cytology

Figure

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  Fig. 1. Radiologic and gross findings. (A) Ga-enhanced T1-weighted magnetic resonance imaging shows a transdiploic mass in the frontal scalp involving the dura mater (arrow). (B) Grossly, an ill-circumscribed, whitish solid mass infiltrates the skull (circle).

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  Fig. 2. Representative images of squash cytology, histologic, and immunohistochemical findings. (A) On frozen section, tumor clusters with smear artifacts are scattered in a clear background. (B) Epithelioid cells with abundant cytoplasm and prominent nucleoli are identified. A few spindle-shaped cells (arrowheads) and binucleation (arrows) are noted. (C) Marked nuclear pleomorphism and mitosis (arrow) are observed. (D) In permanent section, the epithelioid cell component shows glassy cytoplasm with a solid pattern. (E) Spindle cell component shows a fascicular pattern. Tumor cells express immuno-positivity for desmin (F), MyoD1 (G), cytokeratin AE1/AE3 (H), and anaplastic lymphoma kinase (I). Cytokeratin is expressed in not only epithelioid cells but also spindle cells (arrows, H).

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  Fig. 3. Results of break-apart fluorescence in situ hybridization. (A) EWSR1 rearrangement is identified (circles). (B) Anaplastic lymphoma kinase copy number change or translocation is not observed. (C) TFCP2 break-apart signals are detected in a few tumor cells (circles). Seven of 100 cells present a splitting signal on counts, indicating a negative result.

Reference

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