DefinitionThis section has been translated automatically.
Heterogeneous group of tumours that originate from the hair follicle epithelium and mimic the cells of a developing embryonic hair germ. With a rather monomorphic and uncharacteristic clinical picture they show an extraordinarily large histological variability, which often makes their exact classification difficult. In addition, there are difficulties due to historically determined, different nomenclatures.
ClassificationThis section has been translated automatically.
The classification presented here, which has been varied and extended according to Kazakov, is essentially based on the classification principle presented by Ackerman and colleagues.
- Tumours with predominantly follicular germ cell differentiation
- Biphasic epithelial-mesenchymal tumors with differentiation towards follicular germ cells and the specific follicular stromas
- Tumours with predominant matrix differentiation
- Tumours with predominant differentiation towards the outer hair root sheath
- Tumours with predominantly infundibular differentiation
- Tumours with predominantly panfollicular differentiation
- Follicular cysts
- Non-neoplastic or hamartomatous changes
- Basaloid follicular hyperplasia (follicular tumorlet)
- Hair follicle nevus
- Ectopic hair follicles
Note(s)This section has been translated automatically.
Biphasic, epithelial-mesenchymal neoplasias comprise a group of follicular tumors that develop a double differentiation towards the follicular germinal epithelium and the specific follicular mesenchyma. The prototype of such a biphasic hair follicle tumor is the trichoblastoma. The premalignant fibroepithelioma (Pinkus tumor) also belongs to the group of biphasic epithelial mesenchymal neoplasias, although this tumor is usually listed among the variants of basal cell carcinoma.
Tumours with predominantly matrix differentiation mimic the structures of the normal follicular bulb. The prototype is the pilomatrixoma (previously: Epithelioma calcificans Malherbe) and a related melanocytic variant, the melanocytic matrixoma.
Cystic structures are often expressed during infundibular differentiation. In epithelial differentiation a stratum granulosum is expressed. A typical representative is the trichoadenoma.
Tumours with panfollicular differentiation express all parts of the hair follicle. An example of this is the trichofolliculoma.
In addition to the true follicular neoplasias, there is a heterogeneous group of hamartomas as well as cystic and non-cystic follicular hyperplasias.
LiteratureThis section has been translated automatically.
- Ackerman B et al (2001) Neoplasms with follicular differentiation. Ardor Scribendi, New York
- Headington JT (1976) Tumors of the hair follicle. A review. On J Pathol 85: 481-503
- Kaddu S et al (2003) Adnexal tumors with hair follicle differentiation. In: Kerl H et al (ed.) Histopathology of the skin. Springer, Berlin Heidelberg New York, S. 651-669
- Kazakov d (2016) Adnexal tumors with sebaceous gland and hair follicle differentiation. In: Cerroni L et al (eds.) Histopathology of the skin. Springer, Berlin Heidelberg New York, S 670-671
Incoming links (10)Adnextumors of the skin (overview); Dilated pore; Hair follicle tumor; Multiple Trichoepithelioma ; Pilomatrixoma; Trichilemmoma; Trichoadenoma; Trichodiscom; Trichoepithelioma, desmoplastic; Trichofolliculoma;
Outgoing links (22)Basal cell carcinoma (overview); Comedonic nevus; Dilated pore; Hair follicle nevus; Keratosis, trichilemmal; Matrixoma melanocytic; Milia (overview); Multiple Trichoepithelioma ; Nasal papilla fibrosus; Pilomatrix carcinoma; ... Show all
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