Subungual melanoma is the most common form of acral–lentiginous melanoma, a malignant tumor of the skin of the fingers that develops in the area of the nail bed. The neoplasm in the initial stage has the appearance of a dark brown or black stripe, which occupies most of the nail plate, passes to the roller and the skin of the fingertip. As the node grows, the nail plate deforms, ulcerates, bleeds easily when damaged. The diagnosis is made on the basis of histological examination data. Treatment involves surgical removal of the affected phalanx, a course of chemotherapy or radiation therapy. In advanced cases, palliative treatment.
Representatives of the Mongoloid and Negroid races have a 40% higher risk of developing the disease compared to Europeans. The average age of patients diagnosed with subungual melanoma is 67±1 year for women and 63±3 for men. The correct diagnosis at an early stage of the disease when contacting a dermatologist is made by about 3% of patients. The 5-year survival rate in case of initiation of treatment at the first stage is 74%, at the second – 43%. In 40% of cases, non-pigmented formations are detected, which makes diagnosis difficult.
The peculiarity of the acral-lentiginous form of melanoma is the fact that its development is provoked not by ultraviolet radiation, but by other adverse external influences. The analysis of numerous clinical observations did not reveal a connection between subungual melanoma and excessive insolation. The causes of the development of pathology include:
- Mechanical damage. A third of patients have a history of nail phalanx injury. The big toes, the thumb and index fingers of the working hand are more often affected. Cosmetic and surgical interventions that are performed for nail diseases can “start” tumor growth.
- Physical and chemical effects. Frostbite and burns play a primary role in the development of subungual melanoma. The cause of relapse is often an attempt to remove the neoplasm with a laser. 7.5% of patients had long-term contact with aggressive chemical and radioactive substances in the past (occupational hazards).
- Hereditary predisposition. Genetic defects that can lead to the development of melanoma are detected in 5-14% of patients. Disorders underlying the development of familial melanoma affect the cell cycle regulation genes CDKN2A and CDK4, the melanocyte homeostasis gene MTF, a number of low-tolerance genes, for example, MC1R.
In 20% of cases, melanoma develops against the background of existing congenital or acquired complex, borderline, intradermal, blue nevus. Predisposing factors in representatives of the Caucasian race include light skin phototype, red hair, the presence of freckles, multiple dysplastic nevus. In Asians and Africans, the sub-elbow localization of education accounts for 50% of all cases of melanoma, in Europeans this indicator is 2%.
A whole spectrum of activating mutations, chromosomal disorders that occur sequentially, triggers the development of subungual melanoma. Suppressor genes and oncogenes are involved in the pathological process. The probability of damage to chromosomes and individual genes increases under the influence of radiation, aggressive chemical compounds, chronic tissue injury.
At the molecular level, changes primarily affect the expression of components of the plasminogen activation system, the activity of growth factors. At different stages of the tumor process, the concentrations of insulin-like growth factor, endothelial growth factor, fibroblasts, transforming growth factor change, and the number of receptors for these biologically active substances increases.
Disorders are detected both in the tumor node itself and in perifocal tissues, which indicates the involvement of surrounding structures in the pathogenesis, metabolic instability of skin cells located on the periphery of the neoplasm. The presence of a metabolically altered tumor area determines the scope of the surgical operation.
Several classifications have been developed and used in oncodermatology, which take into account the histological structure of the tumor node, the number of dividing cells and other parameters. Classification according to A. Breslow is based on the thickness of the neoplasm in millimeters. The Clark penetration level includes five degrees of invasion of melanoma of the nail bed into the skin structures:
- First. The malignated cells are located in the epidermis and do not spread deeper than the basement membrane. This is the most favorable form of the sub-elbow tumor node in terms of the prognosis of recovery, since there are no metastases at this stage yet.
- Second. Cancer cells penetrate into the upper layers of the papillary layer of the dermis. The basement membrane is being destroyed. The tumor node becomes large enough for its visual detection.
- Third. Altered melanocytes fill the entire papillary layer of the dermis, but are not yet detected in the retina.
- Fourth. The neoplasm grows into the mesh layer of the dermis.
- Fifth. Invasive melanoma growth is observed in subcutaneous adipose tissue. Atypical cells actively spread by lymphogenic and hematogenic pathways.
Subungual melanoma symptoms
A growing cancerous tumor has a negative effect on the entire body. Changes in the work of the immune system, pronounced intoxication, destruction of the tumor node and the tissues surrounding it, leads to the appearance of a whole complex of local and systemic manifestations.
The neoplasm has the appearance of a strip of black or dark brown color, which occupies more than 1/3 of the width of the nail plate. The color of the strip is not uniform. In 30% of cases, Hutchinson’s symptom is detected – the spread of pigmentation on the nail roller, the skin of the phalanx at the free edge of the nail. About half of the observations in the subarticular zone develop non-pigmented melanomas, which remain unnoticed for a long time. In this case, the first symptoms of the disease are signs of dystrophy and deformation of the nail.
The nail plate of the affected finger loses its shine, becomes thinner, becomes brittle, and easily exfoliates. As the cancerous node increases in volume, the nail cracks. Under it is a bumpy surface of brown or black color, which looks like granulation tissue and bleeds easily. The color of the neoplasm may be heterogeneous due to the content of darker inclusions.
Invasive growth leads to the spread of the tumor from the sub-elbow area to the hand or foot, the germination of bones and soft tissues of the phalanges. This provokes the appearance of pain of varying degrees of intensity. Pain syndrome often complicates the movement of patients who cannot lean on the affected limb. In some cases, there is a feeling of bursting, itching and burning in the area of the primary tumor focus.
As the cancer progresses, the general well-being of the patient is disturbed. General weakness is increasing, causeless weight loss is noted, and a persistent increase in body temperature is often observed. The rate of progression of the disease varies widely, however, a year after the first symptoms are detected, the patient may become incurable due to active metastasis of the tumor. Cases have been described when primary melanoma underwent reverse development, and clinical manifestations were due to existing regional and distant metastases.
The tumor is characterized by an unpredictable course. Surgical removal of invasive melanoma does not guarantee the absence of relapses or metastatic foci. Melanoma metastasizes more often to the lungs and liver, its metastases often significantly exceed the primary tumor node in terms of malignancy. Metabolic disorders in advanced forms of the disease leads to the development of cancerous cachexia.
Surgical treatment of a neoplasm of the sub-elbow area involves the removal of the phalanx or the entire affected finger. As a result, a significant defect is formed, noticeable to others, there is a partial loss of functionality of the hand or foot. In 5% of cases, the volume of surgery on the leg has to be expanded to a planar resection of the metatarsal. With stumps of the forefoot, the support of the operated limb decreases by an average of 60%, which creates an additional load on all departments of the musculoskeletal system.
Subungual melanoma is a tumor of visual localization. However, early diagnosis is complicated by the external similarity of a malignant neoplasm with a hematoma, a subarticular nevus, and a cavernous thrombosed hemangioma. A comprehensive analysis of the data obtained during a comprehensive examination of the patient allows you to make the correct diagnosis. The list of physical, laboratory and instrumental tests for suspected melanoma includes:
- General inspection. In most cases, patients with nail changes turn to a dermatologist who collects anamnesis, performs dermatoscopy, checks the condition of regional lymph nodes. He also prescribes an initial examination and recommends a consultation with an oncologist.
- Epiluminescent microscopy. The neoplasm of the skin is examined using a dermatoscope in a special immersion medium in which the stratum corneum of the epidermis becomes transparent. The method makes it possible to distinguish a malignant neoplasm from a benign one with a high degree of probability.
- Ultrasound examination. The scope of the study is determined by the clinical picture of the disease. To detect local metastases, ultrasound of regional lymph nodes is prescribed. In the presence of symptoms from the internal organs, abdominal ultrasound and pelvis is performed. Soft tissue sonography can be prescribed to determine the number and size of metastatic foci.
- Histological examination. The integrity of the tumor should not be violated, as this can lead to the rapid spread of malignized cells throughout the body. If there are defects in the nail plate, smears or prints are taken. A puncture of the lymph node can also be performed in order to identify its micrometastatic lesion.
- Computer and magnetic resonance imaging. These methods of medical imaging are advisable to use in cases where ultrasound is uninformative. MRI of the feet and hands with contrasting allows you to determine the volume of the affected area. Chest CT is indicated for patients with suspected metastatic lesion.
An oncological patient should be under medical supervision throughout his life, receive treatment appropriate to the stage of the disease. Medical tactics are determined by the volume of the primary tumor node, the presence of metastases, concomitant pathology. Cancer recurrence therapy has a number of differences.
The peculiarity of melanoma is its weak sensitivity to radiation and chemotherapeutic effects, so the leading role belongs to the surgical method of treatment. Radiation therapy is prescribed in two cases: irradiation of the scar after removal of a tumor recurrence and exposure to the area of the primary node to prevent transit metastases.
Chemotherapy, depending on the extent of the spread of malignated cells, can be regional or systemic. For its implementation, such drugs as dacarbazine, lomustine, tamoxifen, etc. are used. Different protocols involve adjuvant and non-adjuvant chemotherapy. As a rule, chemotherapeutic drugs are used in the postoperative period in order to reduce the likelihood of relapse, the destruction of malignated cells that may be in the lymphatic system and bloodstream.
The appointment of chemotherapeutic treatment before surgery allows to reduce the size of the tumor, which creates optimal conditions for successful surgical excision of the neoplasm. Histological examination of the removed tissues allows specialists to assess the degree of drug pathomorphosis, i.e. the sensitivity of malignized cells to the action of antitumor drugs.
Detection of subungual melanoma is an indication for radical surgery. The opinions of practicing oncological surgeons regarding the scope of the operation differ. Until recently, it was believed that the higher the amputation was performed, the less likely a relapse was, therefore, exarticulation of the entire finger in the metatarsal or metacarpophalangeal joint was performed.
Currently, using the example of a number of studies, it has been shown that the 5-year survival rate of patients after amputation of the distal and middle phalanges is the same as in patients after exarticulation of the entire finger, while the degree of limb dysfunction is less. Amputation at the level of the middle phalanx of the affected finger is the most preferable.
Two methods are under study: immunotherapy after excision of the neoplasm and gene therapy of the disease. The administration of interferon-alpha, granulocyte-macrophage colony stimulating factor, interleukin-2 in maximum tolerated doses increases the overall survival of patients, contributes to the prolongation of the relapse-free period. Gene therapy involves the introduction of suppressors of the p53 and p16INK4a genes into tumor tissues in order to inactivate the pathological signaling pathway leading to the transition of cells to invasive growth.
Prognosis and prevention
After the treatment, relapses are observed in 60% of patients. The predicted life expectancy of patients with disseminated subungual melanoma is on average 6-8 months. Radical surgery does not improve the prognosis in the presence of metastases. Chemotherapeutic treatment is effective in 15-20% of cases. It is possible to achieve recovery only with early detection of pathology.
All preventive measures are divided into two groups: primary and secondary. Primary prevention includes conducting a genetic examination in patients with familial melanoma, limiting the effects of irritating chemicals, protecting limbs from injury. The secondary involves monitoring the existing nevi and their timely excision. Injury of birthmarks is not allowed, so as not to provoke a malignant degeneration of the formation.