Sebaceous adenoma (AS). It is a rare benign tumor , composed of incompletely differentiated sebaceous lobes, which usually occurs solitary on the face of older people.
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- 1 Aetiopathogenesis
- 2 Classification
- 3 Clinic
- 4 Histopathology
- 5 Differential diagnosis
- 6 Treatment
- 7 Sources
The etiopathogenesis of AS is better known since its presence was linked 25 years ago in Muir-Torre syndrome . In this process, of autosomal dominant inheritance, there is genetic instability due to alteration of some genes responsible for repairing DNA pairing errors. This failure is the cause of the presentation of neoplasms on the skin , being able to add, or not, the presence of keratoacamptoms and internal malignancies, which characterizes the syndrome.
A similar sporadic alteration could be the cause of isolated AS.
AS is classified into benign tumors of epidermal adnexa, in its case with sebaceous differentiation.
Conceptually, as a true benign tumor, it must be differentiated from the Fordyce condition , by the presence of heterotopic sebaceous glands , from the simple hypertrophy of the gland that exists both in sebaceous hyperplasia and in sebaceous nevus, and from the so-called sebaceous epithelioma or sebaceoma of difficult separation of basal cell carcinoma.
Clinically, it manifests as a solitary tumor, generally 0.5 to 1 cm in diameter, with a smooth surface, located on the face or scalp of elderly people.
As clinical diagnostic keys we indicate:
- Slow growing solitary tumor.
- Size 0.5-1 cm, smooth surface and discreetly yellowish coloration.
- Location on the face or scalp of elderly people.
Microscopically, the tumor is characterized by pointed sebaceous lobes, separated by septa of connective tissue. These sebaceous lobes are made up of two types of cells:
- Germ cells (small and dark, corresponding to undifferentiated basalioid cells) as peripheral layer and mature sebaceous cells in the central areas of the lobe; between these two cell types
transitional cells exist and maturation is not as orderly as in normal sebaceous glands
The ratio between basalioid cells and sebaceous cells is variable depending on the case, although mature cells usually outnumber basalioids.
The sebaceous lobes are initially seen in the intermediate dermis, although they sometimes reach the epidermis, and can even produce openings to the skin surface, with partial replacement of the epidermis by a basalioid epithelium with sebaceous differentiation.
There are cases where a central holocrine degeneration, of variable magnitude, is observed, with debris derived from mature sebaceous cells, giving rise to a zone of cavitation (cystic transformation). These cystic sebaceous adenomas usually appear exclusively in patients with Muir-Torré syndrome.
The clinical differential diagnosis must be established with sebaceous hyperplasia and with sebaceous epithelioma. The multiple nature of the former, with typical central depression, usually allows their clinical distinction, while the differentiation of sebaceous epithelioma is histopathological.
Other tumors that should be considered clinically in the differential diagnosis are basal cell carcinoma and many other adnexal tumors.
The histological differential diagnosis must be carried out with pathologies where the sebaceous glands increase or are altered, especially with:
- Sebaceous hyperplasia, consisting of large mature sebaceous lobes without fibrotic septa that have normal sebaceous glands, and sebaceous epithelioma (“sebaceoma”), consisting of nests of basalioid cells, interspersed with sebaceous cells or grouped in clusters, and where cells Sebaceous species outnumber the mature sebaceous component.
In the treatment of AS, it is logically the surgical removal that completely solves it. Its diagnosis forces us to rule out the possibility of Muir-Torre syndrome.