Typical CUP subgroups with a positive clinical outcome include neuroendocrine carcinoma of unknown primary, squamous cell carcinoma involving cervical lymph nodes, single metastatic deposit of unknown primary, papillary adenocarcinoma of the peritoneal cavity in women, isolated axillary nodal metastases in women, and osteoblastic bone metastases and prostate-specific antigen expression in men. This evidence concerns the gene KLK3 and squamous cell carcinoma.