OBJECTIVES: Metastasis of head and neck squamous cell carcinoma (HNSCC) usually occurs regionally in the neck lymph nodes, but also more infrequently at distant organs (eg, the lungs, bone, and liver). Intramuscular metastasis (IMM) has rarely been described. Therefore, we aimed to identify this disease characteristic and to evaluate available medical management options. METHODS: Data of surgically treated HNSCC patients (n = 1150) at the Chi Mei Medical Center, Taiwan (2005-2015), were retrospectively reviewed. Literature searches were also conducted (1985-2015) to analyze the behavior of HNSCC with distant IMMs. RESULTS: We identified 1 HNSCC patient with histopathologically proven IMMs. Ten similar cases were also identified in the available literature. Two-thirds of lesions arose in patients with laryngeal/hypopharyngeal malignancies, and two-thirds of lesions were located in the lower limbs. Lesions were subjectively painful and usually had rim enhancement with central hypoattenuation in contrast-enhanced computed tomography/magnetic resonance imaging. The mean duration between primary tumor diagnosis and secondary lesion detection was 13.7 months. No patient survived more than 2 years after establishing a diagnosis of HNSCC with IMMs. CONCLUSIONS: Distant IMMs are extremely rare in HNSCC patients and have a poor clinical outcome. Differentiating this disease from sarcoma via anatomic distribution or diagnostic imaging studies is not straightforward. Biopsies for histopathologic examination are mandatory. Treatment of HNSCC patients with IMMs is mainly palliative for life quality preservation and not lifetime prolongation. Radiotherapy is established as a first-line treatment for symptom control with surgical intervention usually preserved for refractory cases.
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