Blue nevus (Jadassona-Tiche blue nevus) is an acquired pigmented neoplasm of the skin of a small size, having a characteristic dark blue or blue color. As a rule, such an education is isolated, but in some cases there are also multiple blue nevi. This nevus belongs to benign, but melanoma-threatening formations. In rare cases, it can malignate with the development of melanoma. In the treatment of blue nevus, wait-and-see tactics are usually followed and the removal of the nevus is carried out only with its significant increase or other changes that may be a sign of malignant degeneration.
Blue nevus occurs in people of any age group, but most often appears during puberty. It is characterized by slow growth and does not cause any subjective sensations in the patient, so it can remain unnoticed for a long time. Disease is more common among women than among men.
The blue nevus is a clearly delimited nodule of oval, rounded or fusiform shape located inside the skin. It usually has a size of up to 1 cm in diameter, in some cases nevi of up to 3 cm were observed. The dark blue, blue or blue-black color of the nevus is uneven and is caused by accumulations of a large amount of melanin in the deep layers of the skin. The nevus may rise slightly above the surface of the skin or not protrude above it at all. Looking at it, one gets the impression that there is some kind of foreign body under the skin. The surface of the blue nevus is smooth without hair growth, the consistency is dense and elastic.
The nevus is located on the back of the feet and hands, on the shins and forearms, on the buttocks, less often on the face or in the oral cavity. It usually does not cause itching, soreness or any other sensations. Disease can cause discomfort only if it is located in a place where it is constantly injured. It is possible to suspect the transformation of the blue nevus into melanoma by the changes occurring in it: accelerated growth, color change, decreased clarity of contours, the appearance of unpleasant sensations in the nevus area.
There are simple and cellular forms of blue nevus, as well as combined nevi. A simple blue nevus is a single nodule up to 1 cm in diameter with a smooth surface and a tightly elastic consistency. It can have any color in the range from light gray to black and blue. The favorite location of such a nevus is the neck, face and hands, but it may appear on the trunk, oral mucosa, cervix and vagina.
Cellular blue nevus has large dimensions (1.5-3 cm) and a dark blue color, its surface may be uneven. Because of these features, it is often mistaken for a malignant neoplasm. In half of the cases, cellular nevus is detected on the lower back or buttocks, less often it is located on the back of the feet and hands. A combined nevus is a combination of a simple blue nevus with an intradermal, borderline or complex pigmented nevus.
The small size, pronounced delineation and characteristic color in many cases allow us to immediately assume the diagnosis of blue nevus. For a more accurate diagnosis, dermatoscopy is performed — a visual study of the depth, boundaries and structure of the nevus when magnified. A sciascopic study allows us to determine the nature of the distribution of melanin and to study the structure of the nevus. Disease is differentiated with borderline nevus, dermatofibroma, melanoma. In difficult cases, ultrasound of a skin neoplasm can be used for differential diagnosis with melanoma, which determines the depth of germination and malignant infiltrative growth.
Histological examination carried out after removal of the blue nevus reveals clusters of melanocytes in the middle and lower layers of the dermis. A simple blue nevus is characterized by a cluster of melanin-filled cells. The cellular nevus is represented by large cells with a low pigment content. These cells are grouped into islets separated by connective tissue bridges.
With a calm flow of the blue nevus without sudden changes in its size and appearance, removal of the formation is not required. The owner of the nevus should be monitored and undergo periodic examinations by a dermatologist or dermatooncologist. Surgical treatment is also necessary in cases where the blue nevus is located in such a way that it is permanently injured, which can provoke its malignant transformation into melanoma. Removal of the blue nevus can be carried out by radio wave method, electrocoagulation or cryodistruction. Nevus removal by laser is also used. In doubtful cases, when there are difficulties in differentiating the blue nevus from melanoma, or when changes in the nevus appear, indicating possible malignancy, surgical excision of the nevus is performed. Excision of the nevus is carried out together with subcutaneous fat and a healthy skin area 5-8 mm wide from the visible border of the nevus. When removing the nevus on the face for a better cosmetic effect, the width of the captured area of healthy skin can be reduced to 3-5 mm. The removed nevus is necessarily subjected to histological examination.