Citrulline-Containing Basal Cell Carcinomas: Differentiation Toward Hair Structures With Induction of Dermal Hair Papillae

The study from 1968 found that citrulline was present in keratin derived from the inner root sheath or medulla of hair follicles, but not in other keratins. Keratotic basal cell carcinomas sometimes contained citrulline in their keratin, and these tumors showed a higher presence of dermal hair papilla-like structures compared to those without citrulline. This suggested that such tumors attempted to mimic normal hair growth, indicating a high degree of differentiation and ruling out their classification as squamous carcinomas. These findings could aid in distinguishing between keratinizing basal cell and squamous cell carcinomas, reducing misclassification into the "basosquamous carcinomas" category.