Case Number : Case 2128 - 6 August 2018 Posted By: Limin Yu

FibrofollicuIloma/Tricodiscoma. 

A keratinous cyst with trichilemmal keratinization. Around the main cyst are islands of basaloid cells with papillary mesenchymal bodies. I think this is a solitary trichoepitheioma. Alternative differential diagnoses are cutaneous keratocyst and milia.

Central dilated hair follicle surrounded by many small hair follicles - trichofolliculoma. I think the last photo represents a reaction to ruptured hair follicles, rather than a fibrous and myxoid stromal component.

This is a cystic lesion with epithelial and stromal components, sort of a biphasic cystic lesion. I usually put these types of cystic lesion in the category of fibrofolliculoma / trichodiscoma / folliculosebaceous cystic hamartoma. I do not see sebaceous units attached to the cyst, so i do not think it' s a FCH. The epithelial components look kind of mature so I favor trichodiscoma over fibrofolliculoma. But I think they all represent the opposite ends of the same type of lesion. I would agree with Vincenzo.

Thank everyone for the insightful discussion.  This is a trichofolliculoma for me -- a central cystic lesion with secondary radiating vellus hair follicles.  If this is more fibrous stromal changes, I would entertain the idea of fibrofolliculoma.  Thanks!