J Pathol Transl Med.  2024 May;58(3):141-145. 10.4132/jptm.2024.04.12.

Primary epithelioid inflammatory myofibroblastic sarcoma of the brain with EML4::ALK fusion mimicking intra-axial glioma: a case report and brief literature review

• Kim EE
• Park CK
• Kang KM
• Kwak Y
• Park SH
• Won JK

• KMID: 2555540
• DOI: http://doi.org/10.4132/jptm.2024.04.12

Abstract

An aggressive subtype of inflammatory myofibroblastic tumor, epithelioid inflammatory myofibroblastic sarcoma occurs primarily inside the abdominal cavity, followed by a pulmonary localization. Most harbor anaplastic lymphoma kinase (ALK) gene rearrangements, with RANBP2 and RRBP1 among the well-documented fusion partners. We report the second case of primary epithelioid inflammatory myofibroblastic sarcoma of the brain, with a well-known EML4::ALK fusion. The case is notable for its intra-axial presentation that clinico-radiologically mimicked glioma.

Keyword

Epithelioid inflammatory myofibroblastic sarcoma; Brain; Anaplastic lymphoma kinase; Inflammatory myofibroblastic tumor; Literature review

Figure

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  Fig. 1. Contrast-enhanced magnetic resonance imaging (MRI) glioma study (3.0T) and intraoperative surgical field view. T1 axial (A) and coronal (B) preoperative MRI of the 1.5 cm vividly enhancing mass in the right frontal lobe with no intralesional hemorrhage or calcification. (C) Intraoperative surgical field view during the right frontal craniotomy and tumor removal. (D) Intraoperative 5-aminolevulinic acid uptake in the tumor.

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  Fig. 2. Histomorphology and immunophenotype of primary epithelioid inflammatory myofibroblastic sarcoma (EIMS) in the brain. (A) At low power, the perivascular infiltration of the tumor is apparent. (B) Low power also illustrates the appearance of the tumor to extend from the pia mater (lower left) into the brain parenchyme. (C) At high-power, perivascular growth is still observed, with lymphoplasmacytic infiltrate. EIMS tumor cells have low nuclear-cytoplasmic ratio, owing to their plump cytoplasm, but the absolute size of their nuclei are 3–4 times larger than that of vascular endothelial cells, with some tumor nucleoli the size of nearby lymphocyte nuclei. Vimentin immunohistochemical (IHC) stain was strong and diffuse positive (D), while glial fibrillary acidic protein IHC stain was totally negative (E). (F) Reticulin special stain was negative in the tumor and positive in the stroma. Smooth muscle actin IHC stain was positive (G), while desmin IHC stain was negative (H). (I) Anaplastic lymphoma kinase IHC stain with the 5A4 clone showed the characteristic perinuclear staining.

Reference

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