Background <p>Myofibroblastic sarcoma is a rare malignant tumor of mesenchymal origin. According to the 2020 World Health Organization classification of soft tissue tumors, it is classified as an intermediate-grade (occasionally metastasizing) myofibroblastic sarcoma. The disease predominantly affects deep soft tissues in middle-aged and elderly individuals; cases originating in the neck are extremely rare in clinical practice and carry a high risk of misdiagnosis. This report presents a case of primary fibrosarcoma of the neck, aiming to summarize its imaging and pathological characteristics to provide a reference for clinical practice.</p> Case report <p>The patient was a 79-year-old woman who presented with neck swelling and discomfort that had persisted for several months, with symptoms having recently worsened. Physical examination revealed a neck mass. Ultrasound examination demonstrated an irregular hyperechoic mass on the dorsal aspect of the right thyroid lobe, encasing the common carotid artery and internal jugular vein, with abundant internal blood flow signals, accompanied by bilaterally enlarged lymph nodes of abnormal morphology. Contrast-enhanced computed tomography (CT) of the neck showed the mass invading surrounding structures, with multiple calcifications and lymph node metastases. Ultrasound-guided fine-needle aspiration cytology suggested a spindle-cell malignant tumor. Immunohistochemical staining revealed: cytokeratin (sporadically +), thyroglobulin (thyroid oid transcription factor-1 (smooth muscle actin (-), S-100 protein (-), vimentin ( +), p53 (mutant), P40 (-), P16 (and and a Ki-67 proliferation index of approximately 40%. The comprehensive diagnosis was fibrofibroblastoma.</p> Conclusion <p>This case report demonstrates the typical imaging features and histopathological characteristics of a primary myofibroblastic sarcoma of the neck, which may assist clinicians in deepening their understanding of this rare tumor and improving the accuracy of diagnosis and differential diagnosis.</p>