• Midline developmental cyst found at any point from external urethral meatus to anus
Etiology/Pathogenesis
• Defective embryological closure of median raphe
Abnormal closure of urogenital swellings
• Anomalous separation of columnar epithelium from urethra
Clinical Issues
• Solitary cyst
• Typically < 1 cm in size
• May be located at any point between meatus urethralis and anus
Most frequent location is ventral glans
Microscopic
• Located in dermis/lamina propria
• Most frequently lined by
Pseudostratified columnar epithelium (similar to urethral epithelium)
• Other less frequent lining (focal to extensive)
Mucinous
Squamous
– Keratinizing
– Nonkeratinizing
Apocrine
Ciliated
Top Differential Diagnoses
• Epidermoid inclusion cyst
• Dermoid cyst
• Steatocystoma
• Apocrine hidrocystoma/cystadenoma
Median Raphe Cyst This median raphe cyst is located in the dermis without connection with the overlying surface epidermis .
Medium Raphe Cyst With Squamous Epithelium A minority of medium raphe cysts are lined by squamous epithelium, as shown in this picture. Note the lack of keratinization or a granular layer.
Medium Raphe Cyst With Columnar Epithelium This median raphe cyst is lined by pseudostratified columnar epithelium with mucin-containing cells on the surface . This type of epithelium is seen in the majority of these lesions.
Medium Raphe Cyst: Immunohistochemistry for Cytokeratins The multilayered epithelium is positive for cytokeratin AE1/AE3.
TERMINOLOGY
Definitions
• Midline developmental cyst found from external urethral meatus to anus
is located in the dermis without connection with the overlying surface epidermis 
.
. This type of epithelium is seen in the majority of these lesions.
