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.
