Nevus sebaceous is a benign tumor represented by hyperplastic sebaceous glands and deformed hair follicles, which develops as a result of a local violation of the embryonic development of tissues. It is localized on the scalp and face. Externally, it has the appearance of a hairless plaque of yellow-pink oval or irregular shape with a warty surface. The diagnosis is established on the basis of external examination and dermatoscopy, histological examination. The neoplasm is surgically removed. For small-sized tumors, the use of a laser is allowed.
The disease has a number of synonymous names: progressive adenoma of the sebaceous glands, sebaceous nevus, seborrheic nevus of Yadasson. For the first time in 1895, the pathology was described by the leading dermatovenerologist of Europe, Joseph Jadasson. In 60% of cases, a violation of the development of the sebaceous glands is diagnosed immediately after birth. In the general population, this defect is detected in 0.3% of newborns. In 30% of cases, skin formation develops in early childhood. Another 10% of cases occur in middle and high school age. This skin formation is equally common in patients of both sexes. In 6-30% of cases, benign and malignant tumors develop against the background of seborrheic nevus.
Embryonic development of tissues with progressive adenoma of the sebaceous glands is disrupted due to genetic defects in ectoderm cells. Currently, several types of mutations have been described that can occur spontaneously during intrauterine development or be transmitted to the fetus from one of the parents. The main causes of the formation of the nevus sebaceous include:
- Mutation of ectodermal germ cells. The formation of a site of defective sebaceous glands and other skin appendages is a consequence of genetic disorders in individual stem cells. It is known that DNA mutations in fetal ectodermal cells can be provoked by the human papillomavirus received from the mother.
- Inheritance of a genetic defect. Family cases of sebaceous gland nevus are described, which are associated with loss of heterozygosity in the region of the RTSN gene. The method of transmission of a genetic defect is presumably paradominant, that is, there are patients with skin pathology in every generation.
Nevus sebaceous is one of the complex organoid hamartomas – benign tumors that are tissue anomalies that form during embryonic development. Changes in the tissues of the dermis that cause the appearance of nevus affect the sebaceous glands, epithelium, hair follicles, sweat glands. Proliferation of cells of all structural elements of the skin leads to the formation of a tumor of a characteristic type.
The development of seborrheic nevus is based on a violation of the differentiation of pluripotent cells towards mature apocrine and sebaceous structures due to existing genetic defects. The degree of tissue differentiation disorder may vary during the patient’s lifetime. This feature is associated with the formation of cancer at the site of an initially benign formation. Increased proliferative activity of primary epithelial germ cells, simplification of their structure, progressive loss of specialized functions leads to the development of nevus-associated basal cell carcinomas and other forms of skin cancer.
Most sebaceous nevi occur sporadically, but family cases have also been described. Pathology of the appendages of the skin can be an independent disease or combined with other congenital malformations. Depending on the tissues involved in the pathological process and the features of the clinical picture, three forms of the disease are distinguished:
- Single formations. In the overwhelming majority of cases, a single pathological focus located on the head is detected in the patient. At the same time, there are no other disorders on the part of the nervous system, internal organs.
- Multiple nevi. Cases of multiple common pathological foci that are located throughout the body are described. At the same time, the nevi have a predominantly linear shape.
- Sebaceous nevus with neurocutaneous syndrome. Developmental abnormalities can affect not only the skin, but also the nervous and bone tissue, cause eye pathology. In patients of this group, in addition to characteristic tumors, epilepsy and mental retardation are observed.
Nevus sebaceous is a flat plaque of a rounded or elongated shape of a soft-elastic consistency. The diameter of the formation is from 1 to 9 cm . The surface of the plaque is shiny, less often with keratotic layers, densely covered with papillae, hemispherical and warty papules of pink or yellowish-brown color. There is no hair on the surface of the plaque.
The favorite localization of Jadassohn’s nevus is the face and scalp, parotid region and neck. In clinical dermatology, cases of sebaceous nevi of other localizations have been described, but the frequency of occurrence of atypically located neoplasms is extremely low. In most cases, the skin pathology is congenital, less often develops in childhood. Over the years, the surface of the plaque undergoes significant changes.
In young children, the nevus area is smooth, pale pink, slightly rises above the surrounding unchanged tissues, may be barely discernible or covered with small papillae. In adolescence, the skin in the affected area thickens, the surface of the plaque is covered with warty papules that fit snugly together. At this stage, the apocrine glands ripen, the sebaceous glands develop noticeably, and warty hyperplasia of the epithelium occurs.
In every fifth adult patient, a benign or malignant tumor forms in place of the plaque, which changes the clinical picture of the underlying disease. In the process of maturation, the nevus does not cause discomfort to its owner: it does not hurt, does not bleed, does not increase in size and does not itch.
The most common type of benign neoplasia developing against the background of Jadasson’s nevus is trichoblastoma. It accounts for 5% of all nevus-associated tumors. In second place is syringocystadenoma. The incidence of basal cell carcinoma is about 1%. Also, proliferating tricholemal cyst, nodular hydradenoma, squamous cell skin cancer are detected in the area of the sebaceous nevus.
A feature of nevus-associated neoplasias is their appearance in young and middle-aged patients, slow growth and small size of tumor nodes. Skin cancer that has developed against the background of sebaceous nevus is characterized by a low degree of aggression, metastasizes much less often than usual. In children, malignant tumors are not formed. The likelihood of developing cancer increases with age.
It is not difficult to diagnose Yadasson’s nevus. However, even a long-term education does not bother patients, and the pathological focus can be hidden under the hair. This is the reason that patients often seek the advice of a dermatologist already with malignancy of their existing formations. Diagnosis of the nevus sebaceous involves:
- General inspection. During a dermatological examination with dermatoscopy, characteristic skin changes are revealed: acanthosis, underdevelopment of hair follicles, papillomatous outgrowths of the epidermis. According to the appearance of the pathological focus, it is possible to assume the type of nevus-associated benign or malignant tumor.
- Histological examination. The leading pathohistological sign of congenital pathology of the skin in children is the presence of undifferentiated hair structures, in later periods – the presence in biopsies of hypertrophied sebaceous glands without excretory ducts, papillomatous hyperplasia of the epidermis.
Differential diagnosis of Jadasson’s nevus is performed with syringocystadenous papillary nevus, juvenile xanthogranuloma. Seborrheic nevus in children differs from skin aplasia by a smoother papyrus-like surface. Solitary mastocytoma has a histological structure different from progressive adenoma of the sebaceous glands. Dermatooncologists and surgeons may be involved in the examination.
There are no cases of malignant transformation of seborrheic nevus before puberty. In this regard, it is recommended to remove the skin formation in a timely manner. Different methods of surgical treatment differ in the effectiveness of tumor removal, aesthetic results of intervention. For the treatment of nevus and tumors that have developed on its background , the following are used:
- Surgical excision of the formation. The method allows you to remove tumors of any size. Seborrheic nevus is removed under local anesthesia to the level of subcutaneous fat or tendon helmet. Malignant neoplasms require an extended surgical operation to prevent the recurrence of tumors that can grow invasively, metastasize.
- Application of methods of physical influence. The CO2 laser is used to remove pathological foci of a small area without signs of malignancy. Electrocoagulation and cryodestruction can be used to remove small benign tumor foci on the face and neck, where the appearance of scars is undesirable.
Prognosis and prevention
Methods of preventing the appearance of sebaceous gland nevi have not been developed, since their development is associated with genetic defects of cells. A high risk of malignant degeneration of the sebaceous nevus is an indication for its removal. The age of the operation is determined by the localization of the formation. The second most important reason for surgical treatment is the characteristic appearance of the tumor, which is regarded as a flaw.
On the head, the formation is hidden by the hair, so the removal of the nevus sebaceous can be postponed until the beginning of adolescence. Before this period, dynamic observation of the pathological focus by a dermatologist is recommended. In the face and neck area, the risk of scarring of wounds at the site of removed seborrheic nevi is lower in children, which is a determining factor in deciding whether to perform surgery.