Erythroplasia of Queyrat is a term used to describe a rare premalignant lesion of penile in situ squamous cell carcinoma. The glans is the predominant location of this lesion, and its non-specific presentation - a sharply defined red patch or plaque, may often lead to a misdiagnosis as one of many mucosal dermatoses. A biopsy with subsequent histopathological examination is necessary to confirm the diagnosis.
Initially described more than 100 years ago, Erythroplasia of Queyrat (EQ) is a distinct clinical entity denoting a pre-cancerous lesion of the squamous cell carcinoma (SCC) in situ of the penis  . It is rarely encountered in clinical practice and appears on the penile mucosal surfaces - the glans, coronal sulcus and prepuce, while the urethral meatus is also reported as a potential site  . Many studies have classified Bowen's disease (BD) and EQ as the same entity because of their striking similarity on histological examinations, but the different location of BD (mainly seen on the skin of the penile shaft) differentiates the two terms in the majority of literature  . Elderly patients are the principal population in whom EQ is diagnosed, and the presence of a phimotic foreskin, as well as an uncircumcised penis, are considered to be risk factors, as they are encountered in the vast majority of patients  . The typical presentation involves a well-demarcated, shiny, bright-red, or red velvet-colored patches or plaques (either solitary or multiple) that are painless, although erosions may be noted   . However, because these lesions resemble numerous dermatologic conditions (including psoriasis, dermatitis, any of the sexually transmitted infections that present in a similar fashion, lichen planus, Zoon's balanitis, etc), the diagnosis might be initially missed     .
The importance of recognizing EQ early on lies in the fact that penile in situ squamous cell carcinoma (SCC) can arise from up to a third of patients who develop this lesion and approximately 20% of SCCs develop distant metastases    . Furthermore, 5-year survival rates of invasive SCC range from 66%-27%, depending on the stage . For these reasons, a meticulous physical examination of the penis and the genitalia is perhaps essential in recognizing EQ. As the presentation is nonspecific, the initial distinction between Bowen's disease (which is less likely to progress into SCC) and EQ should be made based on the location of the lesion, but a biopsy and subsequent histopathological examination is necessary to rule out other etiologies and confirm EQ as the presenting lesion  . Generalized hyperplasia (acanthosis), the presence of parakeratotic cells with hyperchromatic nuclei, focal erosions, dyskeratosis, and dermal infiltration of inflammatory cells are some of the most prominent histopathological findings described in the literature  .