What is a hyperkeratosis squamas lesion on the foot?

Skin tumor: Hyperkeratosis simply refers to a buildup of skin tissue. However I do not know if you are referring to a hyperkeratotic squamous cell carcinoma which is a serious skin tumor.

Could be several: There are a few possibilities that usually are benign but always should be biopsied to be sure of diagnosis. Some hyperkeratosis squamous lesions include: molluscum contagiosum, plantar warts, seborrheic keratosis, actinic keratosis and squamous cell caricnoma to name a few. But again, they all should be monitored closely and biopsied at discretion of physician.