In a series of nearly 7,000 patients with squamous cell epitheliomas, 2% manifested evidence of metastases at the time of diagnosis.
The regional lymph nodes were the most common sites of this extension but far distant viscera were involved in 5% to 10% of the cases.
Metastases may occur early in such cases: 2.5% had been noted for less than one month, 37.8% for less than six months, and 68.1% for less than one year. This indicates that such spread does not occur only in long neglected or inadequately treated instances.
Epstein E, Epstein NN, Bragg K, Linden G. Metastases From Squamous Cell Carcinomas of the Skin. Arch Dermatol. 1968;97(3):245-251. doi:10.1001/archderm.1968.01610090017003