Cutaneous leiomyosarcoma is a rare malignant neoplasm originating from smooth muscle tissue. It is formed from the muscles of the sweat glands or the muscles that lift the hair. It is a blue, red or yellowish single dense plaque, more often located on the limbs, less often on the head, neck or trunk. The surface of the plaque bleeds easily, ulceration is possible. In the later stages, intense pain in the affected area is often observed. Disease is characterized by a high tendency to relapse, hematogenous metastases are possible. The disease is diagnosed on the basis of biopsy data. Treatment – surgery, radiation therapy, chemotherapy.
Cutaneous leiomyosarcoma is a rare malignant tumor. Leiomyosarcomas of all localizations account for 2.3% of the total number of superficial neoplasms, while cutaneous neoplasia is diagnosed much less often than tumors of similar origin located in the uterus, gastrointestinal tract and retroperitoneal tissue. The share of leiomyosarcomas of the skin in the structure of all soft tissue sarcomas accounts for about 7%. There are leiomyosarcomas of the skin itself and subcutaneous tissue, which differ somewhat in the course and features of metastasis.
Neoplasm is usually detected in patients 40-60 years old, less often develops in children and senile patients. The literature describes two cases of cutaneous leiomyosarcoma in children aged 5 months and one at the age of 6 years, however, such an early onset is considered as casuistic cases. Men and women suffer equally often. Despite the rapid progression and high tendency to recurrence of neoplasia, the prognosis for cutaneous leiomyosarcoma is considered relatively favorable. Hematogenous metastases usually appear when the tumor is located in the subcutaneous tissue. Lymphogenic secondary foci are uncharacteristic. The treatment is carried out by specialists in the field of oncology and dermatology.
The causes of the development of cutaneous leiomyosarcoma have not been established. Experts consider high doses of ionizing radiation and constant traumatization of soft tissues provoking mutation of smooth muscle cells to be the alleged risk factors. At the same time, only a small number of cases have been described in the literature when cutaneous leiomyosarcoma developed against the background of chronic soft tissue damage or previous irradiation. There is also a theory according to which leiomyosarcoma can occur as a result of malignant sarcomatous degeneration of leiomyoma, but convincing evidence of this theory is not yet available.
Macroscopically, cutaneous leiomyosarcoma is a node or plaque of a bluish, reddish or sandy hue with a diameter of 1.5 to 5 centimeters or more. The surface of the cutaneous leiomyosarcoma is smooth, it bleeds easily during trauma. In some cases, hemorrhages and areas of ulceration are found on the surface of neoplasia. The surface layers of the neoplasm usually do not have a clear border with the surrounding healthy tissues. A pseudocapsule is often detected in the subcutaneous layers of cutaneous leiomyosarcoma.
The microscopic picture depends on the level of differentiation of the tumor. The cells of highly differentiated leiomyosarcomas of the skin are oblong, arranged in the form of intersecting bundles, sometimes form a kind of “palisade”. The nuclei are cigar-shaped, localized in the center of the cells. In the study of low-differentiated leiomyosarcomas of the skin, randomly located giant multinucleated cells of various shapes are revealed. The number of mitoses may vary. Myxoid changes and hemorrhagic necrosis are not typical for cutaneous leiomyosarcoma. According to its histological picture, the tumor may resemble other malignant formations of the dermis.
At the initial stages of the disease, patients complain of the presence of a tumor-like formation, usually localized on the extensor surface of the lower or upper extremities. More than half of the leiomyosarcomas of the skin are located on the legs, while the hips are affected more often than the shins. In about 25% of cases, neoplasms are detected in the neck or head. The external genitalia are extremely rarely affected. Cutaneous leiomyosarcoma is a single node or plaque of dense elastic consistency with clear contours, in some cases there are multiple lesions.
About a third of patients suffering from cutaneous leiomyosarcoma report soreness or hypersensitivity in the area of neoplasia. The prevalence of pain syndrome increases as the process progresses, intense pain is possible in the terminal stage. With progression, local symptoms are supplemented by general symptoms of cancer. There is weakness, increased fatigue and loss of body weight. Leiomyosarcomas of the skin rarely metastasize. When tumors are localized in subcutaneous tissue, secondary foci are detected in 30-60% of patients. Bones and lungs are usually affected, lymphogenic metastasis is uncharacteristic.
Due to the low prevalence of cutaneous leiomyosarcoma, the diagnosis, as a rule, cannot be established on the basis of clinical symptoms. The main role in the diagnosis of the disease is played by histological examination data.
Differential diagnosis of cutaneous leiomyosarcoma is more often performed by dermatooncologists with fibrous histiocytoma, subcutaneous leiomyosarcoma – with hemangioperiocytoma. Sometimes the neoplasm has to be differentiated with sarcoma, carcinoma, fibrosarcoma, dermatofibrosarcoma, angiosarcoma, leiomyoma, Kaposi’s angioretyculosis and other tumors.
With an ambiguous histological picture, an immunohistochemical study is performed, the presence of cutaneous leiomyosarcoma is indicated by the expression of desmin and muscle-specific antigen. If hematogenous metastasis is suspected, chest x-ray and skeletal bone scintigraphy are prescribed.
Treatment is usually surgical. The tumor is excised from 2 cm of the surrounding unchanged tissues. When neoplasia is located in the subcutaneous tissue, the pseudocapsule is completely removed. After excision of cutaneous leiomyosarcoma, an urgent intraoperative histological examination is performed, if malignant cells are detected in the incision area, the volume of the operation is increased. Due to the low probability of lymphogenic metastasis, regional lymph nodes are removed only if there are signs of tumor spread along the lymphatic pathways.
Surgical intervention can be supplemented with pre- and postoperative radiation therapy. With leiomyosarcomas of the skin with a diameter of more than 5 cm, preoperative radiotherapy is considered an obligatory stage of treatment, which allows to reduce the volume of subsequent surgery and reduce the risk of relapses. Chemotherapy is prescribed in the presence of metastases. In some cases, chemotherapy drugs are used for preventive purposes, to prevent metastasis. In isolated local recurrences of cutaneous leiomyosarcoma, neoplasia is excised with a wide grip of the surrounding tissues. Radiotherapy is carried out. If there are sufficient indications, amputation of the limb is performed. Single metastases in the lungs are surgically removed. In case of multiple hematogenous metastases, surgical treatment is not indicated.
In the absence of secondary foci, the prognosis is relatively favorable. The risk of recurrence of cutaneous leiomyosarcoma ranges from 40 to 60%, while recurrent tumors in subcutaneous tissue in 30-60% of cases are combined with distant metastases, and when the neoplasm is located in the skin, metastasis is quite rare. In the presence of metastases, in most cases, a fatal outcome is observed. The effectiveness of chemotherapy is noted in 20% of patients with metastases of cutaneous leiomyosarcoma, the average life expectancy is about 1 year.