Pilomatrixoma is a tumor of a complex structure, which presumably develops from the cells of the hair matrix. It is a cluster of non-nuclear cells of the squamous epithelium with areas of fibrosis, calcification, ossification. By the nature of growth, as a rule, benign, less often primary malignant. Externally, the pilomatrixoma is a slow–growing dense solitary node located under the skin. The neoplasm does not cause the patient concern until it reaches a significant size. The diagnosis is established on the basis of examination data, CT, MRI, ultrasound and histological examination. Surgical treatment: the node is removed under local anesthesia.
D23 Other benign skin neoplasms
In the medical literature, the neoplasm has a number of synonymous names: tricholemmoma, pilomatricoma, necrotizing or calcified Malerba epithelioma, calcifying nevus. The disease was first described by French doctors Schoenants and Malerbe in 1880 as a tumor of the sebaceous gland. Most of the pilomatrix (60%) are diagnosed before the age of 20, of which about 40% are in children under 10 years old. Neoplasm may appear in mature and elderly patients against the background of an existing epidermal cyst. Pilomatrixoma is more often found in women. Malignant degeneration of the neoplasm is characteristic of male patients.
According to statistics, Malherbe epithelioma is quite rare. It is difficult to establish for certain the causes of its occurrence. Researchers agree that the basis of the development of the disease is a violation of the natural process of cell division and death. The main reasons for the transition of tissues to neoplastic growth include:
- The influence of occupational hazards. The role of a number of damaging factors in the genesis of calcifying nevus has been proven: ultraviolet and X-ray radiation, toxic chemicals. As a rule, harmful factors are associated with a person’s professional activity, since the duration and intensity of exposure matter.
- Chronic inflammatory processes in the skin. Pilomatricoma develops more often in patients with radiation, chronic solar dermatitis, eczema. It is possible to form pilomatricoma on the site of long-existing epidermal cysts.
- Injury. Cases of the appearance of pilomatricum on the site of postoperative scars, abrasions, burns are described. Activation of metabolic processes in case of damage becomes an impetus for the onset of tumor development. Chronic traumatization of the skin is also important, especially in cases where it leads to the formation of traumatic dermatitis.
In the literature there are indications of family cases of pilomatrix development, as well as tumors associated with chromosomal diseases. Predisposition can be realized at any age, but more often the disease manifests itself before adulthood. The probability of developing calcifying nevus is higher if the patient has Turner, Gardner, Rubinstein-Tybee syndrome, myotonic dystrophy or trisomy 9.
The association of the development of pilomatrixoma with a high level of free beta-catenin, a substance that stimulates cell division and prevents cell death, has been established. An increase in the level of beta-catenin may be due to genetic defects, in which the process of degradation of this protein is disrupted, its active accumulation occurs in the cytoplasm and the nucleus of cells. As a result, the probability of neoplastic growth increases.
The development of the neoplasm is caused by the proliferation of cells of the immature hair matrix, which tend to keratinize. The theory that the pilomatrixoma is a consequence of the transformation of the sebaceous gland or its embryonic germ is currently considered untenable. Active cell division leads to the gradual growth of the node. A loose capsule is located outside the node. Small areas of keratinization are formed in its thickness. Granulations, foci of fibrosis, calcification are located around these epithelial masses, sometimes bone beams are formed. Necrosis foci appear near the keratinization sites.
Pilomatrixoma is a rare type of basal cell epithelioma. Based on the speed and nature of growth, the ability to metastasize, benign and primary malignant skin formations are isolated. They differ in clinical manifestations and in the prognosis for the patient regarding life and recovery:
- Benign pilomatricoma. It occurs mainly at a young age. It is a node with a diameter of up to 4 cm, which slowly increases in size. The tumor has clear boundaries and pushes the surrounding tissues apart as it grows. Cancer rebirth is possible, but it happens quite rarely.
- Malignant pilomatricoma. Most cases of primary malignant Malerbe epithelioma are diagnosed in elderly and middle-aged male patients. It differs from benign pilomatrixoma by rapid invasive growth, significant size (up to 20 cm), softer consistency due to the fact that pathologically altered tissues do not have time to be impregnated with calcium salts. It metastasizes mainly to the lungs and bones.
Benign tricholemmoma is localized on the face, head, neck, shoulders, and rarely the upper extremities. As a rule, it is represented by a single neoplasm. Cases of simultaneous appearance of two or three Malherbe epitheliomas are extremely rare. Cases of multiple pilomatricomas are not described in the literature. In the initial stage, the pilomatrixoma is located in the deep layers of the skin, invisible to others and the patient himself. It is possible to identify a neoplasm when it reaches a size of 5 mm or more.
For a long time, the skin formation grows slowly and does not give the patient unpleasant sensations. The knot is oval or spherical in shape, with clear borders, is not soldered to the surrounding tissues, it will easily mix when pressed. The density of the knot resembles a pebble or a fragment of bone. There are no unpleasant sensations when touching and pressing. The skin above the formation of a small size is not changed, it may be hyperemic.
The clinical picture changes when the diameter of the neoplasm reaches 3 cm or more. The mobile dense formation begins to rise noticeably above the surface of the skin. On the face, there is often redness of the skin, peeling, and the formation of a crust over the tumor node. Gradual atrophy and thinning of the skin is possible. Compression of nerve endings by a dense formation causes a feeling of numbness, soreness, itching, burning, tingling.
Primary malignant pilomatricoma is located on the scalp, neck, in the parotid and post-parotid areas. Less common are formations on the chest, the back of the hands, and the lower extremities. The tumor node is covered with thinned atrophied skin, the consistency is from soft to dense, depending on the degree of calcification of the tissues. The rapid growth of the formation leads to insufficient blood circulation inside the node, the formation of necrosis sites, cysts, ulceration of the skin above the tumor.
Frequent complications of calcifying epithelioma are inflammation and ulceration. It is believed that these changes indicate a cancerous degeneration of an initially benign neoplasm. The formation of an ulcer at the site of a pilomatrixoma is also possible if the formation has reached a significant size. Thinning and atrophy of the skin leads to the formation of a fistula. At the same time, the tumor does not disappear, since the calcified masses do not come out through the fistula.
As a result of incomplete removal of altered tissues during surgical treatment, malignant transformation of the pilomatrixoma by basal cell type, the onset of invasive growth, the formation of metastases is possible. Malignant pilomatrixoma actively metastasizes, which is the main cause of death of patients. Damage to the shell can cause a recurrence of pilomatricoma in the postoperative period.
According to statistics, the correct diagnosis in the case of a typical Malherbe epithelioma is made in 1 out of 50 observations. This formation in appearance and histological structure has much in common with basal cell carcinoma, epidermal cyst, fibroma, skin cylindroma, atheroma. Differential diagnosis of pilomatrixoma in clinical dermatology is based on the evaluation of the data of a comprehensive examination of the patient:
- General inspection. Visual examination and palpation data help to make a diagnosis. What matters is the slow growth of education, its mobility and density. The study of the condition of the skin over the node during dermatoscopy is necessary for the differential diagnosis of pilomatrixoma with basal cell and spinocellular epitheliomas.
- X-ray examination. Computed tomography of the tumor node location area, MRI or routine X-ray examination is performed. The location of the tumor on a woman’s breast is an indication for mammography. According to X-ray images, it is possible to judge the size and nature of the growth of the formation, the presence of metastases. An important diagnostic feature: the ring-shaped shadow of the capsule on the periphery of the formation.
- Ultrasound examination. Soft tissues ultrasound with X-ray examination allows to identify foci of calcification and ossification. The advantage of the method is the ability to examine the area of the location of regional lymph nodes for timely detection of metastases. This makes it possible to distinguish between benign and malignant neoplasms, to detect invasive tumor growth.
- Microscopic examination of tumor tissue. Histological examination reveals foci of fibrosis and calcification of tissues, along the periphery of which giant cells are located. The malignant nature of the tumor is indicated by a large number of mitoses (more than 30), the germination of subcutaneous fat by tumor cells, vascular and lymphatic invasion.
The removal of the formation is carried out by general surgeons and maxillofacial surgeons. The main goal of treatment is to eliminate the neoplasm in such a way as to prevent recurrence and other complications, and when the tumor is located on the face and neck, to avoid the formation of a noticeable cosmetic defect. In practice , the following methods are used:
- Surgical excision. Node removal is performed on an outpatient basis in a classical way or using a laser scalpel. Without fail, the surrounding tissues are removed along with the tumor in case the neoplasm has invasive growth. The tumor itself is delivered to the laboratory for examination. Immediately after the operation, the patient can go home.
- Curettage. The method of curettage of altered tissues and necrotic masses allows you to quickly remove the tumor in the presence of a fistula or ulceration. However, the probability of relapse and other complications with it is as high as possible compared to other methods. The reason for this is the damage and incomplete removal of the pilomatrixoma capsule.
- Cryodestruction and electrocoagulation. The use of these methods is possible only in cases when the diameter of the node does not exceed 5-7 mm. The procedure is performed under local anesthesia. Suturing is not required. An atrophic scar may remain at the site of the formation. The advantage of electrocoagulation is that during the procedure it is possible to obtain node tissue for histological examination.
Prognosis and prevention
A benign pilomatrixoma of a small size is a cosmetic defect that can exist for decades in a relatively unchanged form. Metastasis of a malignant skin formation quickly leads to death. At the same time, diagnostic criteria for the onset of metastasis for Malherbe epithelioma have not been developed.
Timely detection and removal of the node avoids complications. After surgical intervention at the site of a removed benign tumor, relapses are extremely rare. The appearance of pilomatrix of another localization is not excluded. Prevention of the occurrence of tumors is the timely treatment of skin diseases, the elimination of harmful factors.