Intraarticular Inflammatory Myofibroblastic Tumor of the Left Knee With ALK-CARS Fusion Detected With Archer Fusionplex Sarcoma NGS Panel: Case Report and Literature Review

Janet Pineda-Díaz, Irit Solar, Dov Hershkovitz, Ido Drukman, Osnat Sher*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Inflammatory myofibroblastic tumor (IMT) is a lesion of intermediate biological potential with local recurrences and rare metastases found in multiple anatomical locations. We present a case of a pure intraarticular IMT of the knee, a location that has not been previously documented, with genetic confirmation of ALK-CARS fusion detected with next-generation sequencing. A 20-year-old healthy male was admitted to the orthopedic oncology department due to several months of pain and restriction in movement of his left knee. On magnetic resonance imaging, multiple intraarticular nodular lesions were seen. The patient underwent 2 synovectomies within the course of 1 year. The initial biopsy was interpreted as nodular fasciitis. The second biopsy revealed exuberant tissue displaying compact fascicles of spindle cells intermixed with myxoid areas in a background of inflammatory cells, highly suggestive for IMT. Due to the unusual intraarticular location, equivocal ALK immunostaining and the differential diagnosis with nodular fasciitis, we performed targeted next-generation sequencing using Archer FusionPlex Sarcoma panel, which can identify multiple fusions in a single assay. An ALK-CARS fusion was found, supporting the diagnosis of IMT. This report emphasizes the added value of broad molecular analysis in cases with unusual clinical presentation, equivocal immunohistochemistry, and a wide differential diagnosis.

Original languageEnglish
Pages (from-to)216-222
Number of pages7
JournalInternational Journal of Surgical Pathology
Volume29
Issue number2
DOIs
StatePublished - Apr 2021

Keywords

  • ALK-CARS
  • Archer FusionPlex
  • inflammatory myofibroblastic tumor
  • next-generation sequencing

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