Adnexal tumors with hair follicle differentiation D23.L/C44.L

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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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.

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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.

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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.

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  1. Ackerman B et al (2001) Neoplasms with follicular differentiation. Ardor Scribendi, New York
  2. Headington JT (1976) Tumors of the hair follicle. A review. On J Pathol 85: 481-503
  3. 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
  4. 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


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Last updated on: 29.10.2020