Cyst - Altmeyers Encyclopedia - Department Dermatology

Synonym(s)

Cyste

Definition
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Single or multi-chamber cavity, with or without epithelial lining, filled with liquid, gelatinous or solid contents.

Classification
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The present classification is a classification based on histological criteria. A basic distinction is made between epithelial and non-epithelial cysts (pseudocysts). Epithelial cysts can be divided according to their wall structure into:

Cysts with cornified squamous epithelium of the cyst wall:
Cysts with non-cornifying epithelium of the cyst wall:
cysts of the sebaceous glands:
Branchiogenic cysts and fistulas:
Other cystic embryonic malformations:

Non-epithelial cysts (pseudocysts) can be divided as follows:

Cysts on tendons or joints:
Other cysts:
- Mucus granuloma (mucocele)
- pseudocyst of the auricle
- Cyst, metaplastic, synovial.

Note(s)
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The diagnosis cyst is a primary non-classifying clinical diagnosis. The clinician refers to a fluid-filled cavity in the skin or mucous membrane as a "cyst" and does not consider the genesis or etiology, only the clinical picture.
A mucosal granuloma caused by trauma is impressive as a cyst and will therefore be clinically diagnosed as a "mucosal cyst". Likewise the mucoid dorsal cyst, etiologically a traumatic cyst, histologically a pseudocyst (a cavity not lined by epithelium).
A trichilemmal cyst, clinically a coarse knot of the scalp, will hardly be addressed clinically and morphologically as a cyst, although the histological interpretation - trichilemmal cyst - is so.
Cystic tumours (e.g. a cystic basal cell carcinoma) will be clinically addressed as a "cyst". The histological diagnosis, however, is neoplasia and is by no means a contradiction.
The lymphangioma impresses kininically as a cyst. However, the histological diagnosis is not "vascular cyst" but lymphangioma. The same could be said about the so-called lip angioma. Clinically a blood-filled cyst, but the histological diagnosis is angioma. In this respect the clinical-morphological diagnosis "cyst" is not subject to a uniform histological diagnosis.
From a purely histological point of view the term "cyst" is more clearly defined and subdivided. In this respect, all attempts to classify "cysts", which combine clinical, histological and possibly aetiological aspects, are of little use for clinical use.
Cysts are frequent cutaneous lesions that lead to visits to the doctor for various reasons, e.g. cosmetic disorders, mechanical disorders, growth, inflammatory reactions. The definitive diagnosis is generally made after histological examination.