Skin smooth muscle tumors

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Smooth muscle is one of the three muscle groups in the body, next to skeletal muscle and heart muscle. Diseases involving smooth muscle are quite rare, typically leiomyomas, which include both cutaneous leiomyomas and uterine leiomyomas.

1. Characteristics of smooth muscle

In the body, smooth muscle is distributed in different organs, including in the walls of blood vessels (arteries, veins, capillaries), some internal organs (gastrointestinal smooth muscle, uterine smooth muscle .. .), in the skin smooth muscles including the erector muscle and the dartosmus in the scrotum and nipple.
In microscopic appearance, each smooth muscle cell consists of many longitudinal muscle fibers with a rhomboid or cigar-shaped nucleus, without transverse striated fibers. In contrast, with striated muscle and cardiac muscle, there are many transverse striated fibers.

2. Classification of cutaneous leiomyomas

Classification of cutaneous leiomyomas according to malignant or benign nature, leiomyomas have 3 types including:
Benign leiomyoma (leiomyoma) Smooth muscle sarcoma (leiomyosarcoma) Mixed tumor (smooth muscle hamartoma) of organ - part origin, benign cutaneous leiomyomas are classified into:
Piloleiomyoma : leiomyomas originating from the erector muscle. Genital leiomyoma: leiomyoma of genital smooth muscle origin. Angioleiomyoma: vascular smooth muscle tumor. Cutaneous leiomyosarcomas are classified into:
Cutaneous leiomyosarcoma: malignant leiomyomas arising from the erector and genital smooth muscles. Subcutaneous leiomyosarcoma: malignant neoplasm of vascular origin.

2.1. Benign cutaneous leiomyoma (leiomyoma)

Causes of disease
Most of the benign cutaneous leiomyomas are acquired. Only a few are familial and inherited by dominant genes. In women, multiple leiomyoma lesions suggest that fibroids may be present. In addition, some studies suggest that leiomyomas are caused by a deficiency of the enzyme fumarate, which causes loss of function in the gene that encodes the enzyme fumarate hydratease. Fumarate hydratease acts as a tumor suppressor.
Clinical signs
Piloleiomyoma (leiomyomas originating from the erector fascia): Characteristically, lesions are firm, reddish-brown nodules or papules, ranging in size from a few mm to 1 cm, usually on extensor surfaces of the extremities. , in the cheeks or neck. Tumors are often adherent to the skin but can still be mobile, solitary, or combined in painful plaques or clusters, primarily due to nerve irritation and smooth muscle contraction. Pain occurs naturally or sometimes occurs as a result of emotional or psychological changes.

Genital leiomyoma: Lesions consisting of solitary nodules or papules, most commonly in the scrotum, vulva, or breast, often deep subcutaneously or possibly pedunculated. These nodules or papules usually do not cause pain or discomfort to the patient. Angioleiomyoma (vascular leiomyoma): Solitary nodules under the skin cause a lot of pain, the most common location is on the legs, common in women, aged about 30-60 years.

Treatment
Characteristics of benign cutaneous leiomyomas are lesions with a very high recurrence rate, after a period of treatment, new lesions will appear. Specific methods for the treatment of benign cutaneous leiomyomas include surgical removal of the lesion, CO2 laser, cryotherapy... Besides, analgesics, drugs to reduce smooth muscle spasms also help the disease. relieves unpleasant symptoms caused by the disease.

2.2. Skin smooth muscle sarcoma (malignant leiomyoma)

Causes
Unlike benign leiomyomas, cutaneous leiomyomas can often occur after trauma or radiation, rarely as a result of leiomyoma (benign tumour).
Symptoms
Common signs of the disease are large, colorful lesions located in many separate places, located in hairy areas of the lower extremities. These lesions may ulcerate, bleed, and crust with secretions.
Skin smooth muscle sarcomas are usually small nodules less than 2 cm, firmly attached to the upper epidermis. Smooth muscle sarcomas of vascular origin are larger in size, not involving the epidermis. Common signs are pain and itching in the affected areas, which greatly affects the patient's activities.
Prognosis
The vascular smooth muscle sarcoma has a metastasis rate of 30 - 60%, the most common being lung metastasis. Sarcoms originating in the skin have a lower rate of metastasis (5-10%).
Treatment of malignant leiomyoma
The main treatment method is extensive surgery to remove lesions, even amputation.

2.3. Mixed smooth muscle tumor (Hamartoma)

These are mainly congenital or acquired lesions, originating from various components of the skin but mainly smooth muscle. The most common site of injury is the back and extremities. The characteristics of these tumors are often diverse, may be plaques or simple macules, with or without hair follicles, hyperpigmentation, hirsutism, pseudo-Darier's sign (with hair-raising reaction when touching the lesion).
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