• Typically present as multiple small papule(s) on face
Microscopic
• FF shows proliferation of thin, anastomosing epithelial cords
Numerous attachments to follicular structures and epidermis
Typically find central, dilated follicular structure
• TD is stromal-predominant lesion, may show only small/miniaturize follicle
Top Differential Diagnoses
• Tumor of follicular infundibulum
Superficial, plate-like proliferation of bland pale to clear squamoid cells
Anastomosing strands of epithelium present, but usually thicker than those in FF
• Inverted follicular keratosis
Endophytic epithelial proliferation with numerous squamous eddies
Typically shows multiple pseudohorn cysts, suggesting that these are variants of irritated seborrheic keratoses
• Basal cell carcinoma, infundibulocystic type
Basal cell carcinoma shows areas of peripheral palisading and tumor-stromal retraction artifact
Clinical Photograph of Fibrofolliculoma Clinical photograph of a patient with Birt-Hogg-Dubé syndrome shows numerous small, flesh-colored papules on the lateral cheek and neck . (Courtesy J. Wu, MD.)
Fibrofolliculoma at Low Magnification Fibrofolliculoma shows a central dilated (cystic) follicular structure with keratin debris. There are multiple thin, radiating epithelial strands attached to the overlying epidermis .
Fibrofolliculoma With Central Follicular Structure Fibrofolliculoma shows a central follicular structure with a dilated lumen and thin, radiating epithelial strands attached to both the follicle and the epidermis .
Trichodiscoma at Low Magnification Trichodiscoma is composed mostly of fibromyxoid stroma but will often demonstrate a residual miniaturized follicular structure if multiple deeper level sections are examined.
TERMINOLOGY
Abbreviations
• Fibrofolliculoma (FF)
• Trichodiscoma (TD)
Synonyms
• Mantleoma (likely FF variant with sebaceous differentiation)
Definitions
• Closely related hamartomatous proliferations with follicular and mesenchymal differentiation
• Trichodiscoma likely represents late stage in evolution of FF showing stromal predominance
ETIOLOGY/PATHOGENESIS
Genetic Syndrome
• Multiple lesions are strongly correlated with Birt-Hogg-Dubé syndrome (BHD)
Due to mutations in folliculin (FLCN) gene
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. (Courtesy J. Wu, MD.)
.
and the epidermis 
.
