A 68-year-old farmer from rural India presents with a painless, indurated nodule on the dorsum of his right hand that has been slowly enlarging over 2 years. He has a history of chronic sun exposure and a previous actinic keratosis at the same site treated with cryotherapy 5 years ago. Histopathology shows nests of polygonal squamous cells with abundant eosinophilic cytoplasm, prominent intercellular bridges, and invasion through the basement membrane. The structure marked **A** in the diagram is identified as a concentric whorl of keratinizing cells with central acellular keratin. Which of the following best describes the significance of this finding?