Leiomyomas

Leiomyomas are benign tumors derived from smooth muscle cells. They can arise in many organs but are most commonly found in the uterus, where they are known as uterine fibroids, and in the skin as cutaneous leiomyomas. Uterine fibroids are the most common benign neoplasms of the female reproductive system and can be asymptomatic or cause heavy menstrual bleeding, pelvic pressure, urinary symptoms, or infertility.

Pathology and histology: leiomyomas are typically well circumscribed with a whorled, gray-white cut surface. Microscopically they show spindle-shaped smooth muscle cells with elongated, “cigar-shaped” nuclei arranged in intersecting bundles. Mitotic activity is generally low. Immunohistochemistry is usually positive for smooth muscle actin and desmin. The malignant counterpart is leiomyosarcoma, which shows higher mitotic activity, cellular atypia, and necrosis.

Etiology and genetics: growth of uterine fibroids is influenced by estrogen and progesterone and they often grow during reproductive years and shrink after menopause. Genetic alterations are common, particularly MED12 mutations and HMGA2 rearrangements in uterine fibroids. Cutaneous leiomyomas can be solitary or multiple and may occur as part of hereditary syndromes, such as hereditary leiomyomatosis and renal cell cancer (HLRCC) due to FH gene mutations.

Clinical features and sites: uterine fibroids may cause menorrhagia, pelvic pressure, bulk symptoms, or infertility; cutaneous leiomyomas present as painful skin nodules, sometimes triggered by cold or touch.

Diagnosis and management: diagnosis typically involves ultrasound or MRI; biopsy is reserved for uncertain cases or when malignancy is suspected. Treatment ranges from observation for asymptomatic fibroids to medical therapies (gonadotropin-releasing hormone agonists, selective progesterone receptor modulators) and symptom management (tranexamic acid). Surgical options include myomectomy or hysterectomy; less invasive options include uterine artery embolization and MRI-guided focused ultrasound. Prognosis is generally excellent for benign leiomyomas; malignant transformation is rare.