A patient had multiple actinic keratoses previously observed, which developed into clinical squamous carcinoma, on prominently sun-damaged skin. Ten biopsies were performed on lesions of various stages. Four revealed adenoid squamous cell carcinoma. Four others revealed "clefts" which we interpreted as changes in the direction of adenoid differentiation.
Wooldridge WE, Frerichs JB. Multiple Adenoid Squamous Cell Carcinoma. Arch Dermatol. 1971;104(2):202-206. doi:10.1001/archderm.1971.04000200090016