Author: Assoc Prof Patrick Emanuel, Dermatopathologist, Auckland, New Zealand, 2014.
Trichoadenomas (of Nikolowski) are benignfollicular tumours that usually present as slow growing dermal masses. A rare verrucous variant has been described which resembles a benign keratosis clinically.
Histology of trichoadenoma
In trichoadenoma, there is a well defined dermal mass which contains numerous cysts and epithelial strands/islands(figures 1–3). Some of the cysts may rupture and there may be inflammatory changes and calcification. The cysts are lined by a benign infundibulum-like squamousepithelium as seen in an epidermoid cyst (figure 3).
This tumour is highly distinctive. A similar cystic component may be seen within other tumours such as trichoepithelioma and basal cell carcinoma, but the degree of cystification is generally much more extensive in trichoadenoma.
Pathology of the Skin (Fourth edition, 2012). McKee PH, J. Calonje JE, Granter SR
Rahbari H, Mehregan A, Pinkus H. Trichoadenoma of Nikolowski. J Cutan Pathol. 1977;4(2):90-8