Neck Node Squamous Cell Metastasis from Unknown Primary and Mutagen Sensitivity: A Case Series.

Most of the neck node metastases from cancer of unknown primary (CUP) are squamous cell carcinomas (SCCs). The majority of which are human papillomavirus (HPV)-related, frequently show cystic morphology referring to Waldeyer's ring origin. Here, we report four cases of neck node SCCs metastases from CUP. In our institute, 432 patients with head and neck (HN) SCC underwent pretreatment mutagen sensitivity (MS) assay between 1996 and 2006. Among them, 4 patients ≤50 years of age had metastatic cervical nodes from CUP. The primary treatment was cervical node dissection ± radiotherapy. All patients had elevated (>1.0 chromatid break/cell) MS. One male patient died of progressive neck metastasis within 3 years and the 3 female patients are still alive more than 15 years after initial treatment of HPV+ (two) or cystic (one) SCC. Two female patients developed second and third distant site metachronous primary cancers. HPV+ or cystic HNSCC from CUP with elevated MS indicates good outcome. Distant site metachronous cancers of different histologic origins cannot be explained by field cancerization. The clinical significance of elevated MS in neck node SCC metastasis from CUP requires further investigation.