Tumor of the Follicular Infundibulum
David Cassarino, MD, PhD
Key Facts
Terminology
Tumor of the follicular infundibulum (TFI)
Basal cell hamartoma with follicular differentiation
Bland, superficial, plate-like adnexal proliferation with multiple epidermal attachments
Etiology/Pathogenesis
May be sporadic (most cases) or part of Cowden syndrome (multiple, often with tricholemmomas)
Microscopic Pathology
Multiple connections between lesion and epidermis
Cells show abundant pale to clear-staining cytoplasm
Peripheral cells often show palisading
Top Differential Diagnoses
Basal cell carcinoma
Inverted follicular keratosis
Tricholemmoma
 Tumor of the follicular infundibulum (TFI) is characterized by a superficial, plate-like distribution parallel to the epidermis. Note the multiple connections to an adjacent follicular structure  . |
 High magnification of TFI shows a central area of infundibular-type keratinization surrounded by bland squamous cells showing focal cytoplasmic granules  . Note the focal areas of peripheral palisading  . |
TERMINOLOGY
Abbreviations
Tumor of the follicular infundibulum (TFI)
Synonyms
Basal cell hamartoma with follicular differentiation
Mehregan tumor of follicular infundibulum
Definitions
Benign proliferation of mature adnexal keratinocytes showing a superficial plate-like formation with multiple epidermal attachments
ETIOLOGY/PATHOGENESIS
Unknown
Most cases are sporadic
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
