Mesenchymal Chondrosarcoma Presenting as a Calcified Mass Extending Into the Inferior Vena Cava

Area of Science:

• Oncology
• Genomics
• Surgical Pathology

Background:

• Mesenchymal chondrosarcoma (MCS) is a rare, aggressive bone and soft tissue sarcoma.
• Diagnosis and treatment of MCS remain challenging due to its rarity and high-grade nature.

Purpose of the Study:

• To report a case of pelvic mesenchymal chondrosarcoma with inferior vena cava involvement.
• To highlight the diagnostic utility of advanced molecular techniques, including genomic analysis for HEY1::NCOA2 fusion.
• To discuss current and potential therapeutic strategies for this rare malignancy.

Main Methods:

• Patient presentation with lower abdominal pain and imaging findings of a pelvic mass.
• Fluorodeoxyglucose-positron emission tomography (FDG-PET) for staging.
• Tumor biopsy with histopathological examination, immunohistochemistry, and genomic analysis.
• Initiation of chemoradiotherapy due to tumor extent.

Main Results:

• Imaging revealed a large pelvic mass extending from the right internal iliac vein into the inferior vena cava.
• FDG-PET showed intense uptake without distant metastasis (SUVmax 13.97).
• Biopsy confirmed a biphasic tumor with cartilaginous matrix and staghorn vasculature.
• Immunohistochemistry was positive for SMA, desmin, MyoD1, and NKX3.1.
• Genomic analysis identified a HEY1::NCOA2 fusion, confirming mesenchymal chondrosarcoma (MCS).

Conclusions:

• Mesenchymal chondrosarcoma is a rare, high-grade sarcoma with limited therapeutic options.
• The HEY1::NCOA2 fusion is a key molecular driver in this case.
• Targeted therapies directed at HEY1::NCOA2-associated pathways represent a promising avenue for future treatment strategies.