Calluses are formed in the same manner as corns such as repeated pressure or friction due to footwear and bones of the foot. This is due to the skin trying to protect itself during the healing process. Calluses will show a markedly dense orthokerototic stratum underlain by hypergranulosis, mild acathosis, and increased collagenization of the dermis with possible mucin deposition in the dermis.
Castilla, C., Tumer, G., Maghari, A., & Lambert, W. (2019, March 13). Corn/callus (singular: Callus, callosity, tyloma; plural: Callosities, tylomas, tylomata) Clavus (clavi; singular: Clavus, corn, heloma; plural: Corns, helomas, helomata). Retrieved October 31, 2020