Soft tissue aneurysmal bone cyst: six new cases with imaging details, molecular pathology, and review of the literature
Aneurysmal bone cysts (ABC) rarely present in soft tissue locations (STABC). The 30 cases of STABC reported in the English literature were reviewed. Six new cases retrieved from the files of the Netherlands Committee on Bone Tumors were compared to the six cases described in the radiological literature.
Materials and methods
Imaging studies and histopathology of six new STABC cases were reviewed. Follow-up was recorded with respect to local recurrence. FISH for USP6 rearrangement and/or anchored multiplex PCR-based targeted NGS using Archer FusionPlex Sarcoma Panel were attempted.
On imaging, the six STABC cases presented as a solid or multicystic intramuscular soft tissue mass, usually with thin peripheral mineralized bone shell. On MRI, perilesional edema was visualized in nearly all cases. Fluid-fluid levels were observed in one case. All lesions had the distinct histologic features of STABC. In three cases suitable for NGS, the diagnosis of STABC was confirmed by a COL1A1–USP6 fusion gene. In one additional case, USP6 gene rearrangement was detected by FISH. After marginal excision, none of the six STABC recurred after a mean follow-up period of 50 months (range, 39–187 months).
On imaging, it can be difficult to discriminate between STABC and myositis ossificans. The presence of a thin bony shell and fluid-fluid levels can be helpful in discriminating these two entities. STABC is readily diagnosed after histopathologic examination of the resection specimen. STABC belongs to the spectrum of tumors with USP6 rearrangements, which includes ABC, myositis ossificans, and nodular fasciitis.
KeywordsSoft tissue Aneurysmal bone cyst USP6 Radiography CT MRI Ultrasound Radionuclide imaging
Wangzhao Song studied the pathology specimens and drafted the manuscript with Stijn M. Bollen. Albert J. H. Suurmeijer conceived the study, participated in its design, and supervised this article. Anne-Marie Cleton-Jansen performed FISH and next-generation sequencing. Judith V.M.G. Bovée studied the pathology specimens and participated in the study design. Herman M. Kroon conceived the study, interpreted imaging features, designed, supervised, and finally approved this article. All authors read and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
No funds were received in support of this work. The authors declare that they have no conflicts of interest.
Sources of support
W. Song receives funding from the China Scholarship Council (CSC) program (grant no: 201606940023).
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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