Erythroplasia of Queyrat (EQ) is an in situ squamous cell carcinoma of the penis.  The glans and prepuce are most commonly involved. Erythroplasia of Queyrat is seen almost exclusively in uncircumcised men. Progression to invasive carcinoma may occur, and spontaneous regression is unlikely. [2, 3]
Erythroplasia of Queyrat was originally described by Tarnovsky in 1891 and later appreciated as a penile disease by Fournier and Darier in 1893. Studies by Queyrat in 1911 allowed erythroplasia of Queyrat to be accepted as a distinct entity. In 1933, Sulzberger and Satenstein recognized erythroplasia of Queyrat as a form of carcinoma in situ. 
Some references equate erythroplasia of Queyrat with the term Bowen disease of the glans penis”.  The term erythroplasia of Queyrat is used for squamous cell carcinoma in situ (SCCIS) of the mucocutaneous epithelium of the penis. 
Erythroplasia of Queyrat is a rarely reported disorder. It makes up less than 1% of malignancies in males.