DISEASES OF THE UTERUS doc

619

BENIGN UTERINE NEOPLASMS

LEIOMYOMA (MYOMAS,

FIBROIDS, FIBROMYOMAS)

Leiomyomas are discrete, rounded, firm, white to pale pink, benign

myometrial tumors composed mostly of smooth muscle with vary￾ing amounts of fibrous connective tissue. Approximately 95% arise

from the uterine corpus and
5% from the cervix. Only occasion￾ally do they arise from a fallopian tube or round ligament. Leiomy￾omas are the most frequent pelvic tumors, occurring in
25% of

white and
50% of black women by age 50 years. Leiomyomas

account for
10% of gynecologic problems and have their peak in￾cidence in the fifth decade. Although the cause is unknown, each

tumor (98% are multiple) is monoclonal, originating from a single

muscle cell (whether an embryonic cell rest or blood vessel smooth

muscle is unclear). They enlarge in response to estrogen. Thus, en￾largement is marked with pregnancy. Premenarcheal leiomyomas

are rare, and menopause or castration causes regression.

Uterine leiomyomas are classified by anatomic location (Fig. 22-1).

Most commonly they are subserous (beneath the peritoneum),

intramural (within the uterine wall), or submucous (only 5%–10%

are beneath the endometrium). Leiomyomas may become pedun￾culated in either the subserous or submucous locations. A special

variation of pedunculation is retroperitoneal extrusion between the

leaves of the broad ligament (intraligamentous). Although adhesions

to other organs are rare, in extreme cases pedunculated leiomyomas

may derive their entire blood supply elsewhere, becoming parasitic.

PATHOLOGY

Only 2% of leiomyomas are solitary. They may grow to
45 kg.

Each tumor is limited by a pseudocapsule, a potential cleavage plane

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DISEASES OF THE UTERUS

CHAPTER

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BENSON & PERNOLL’S

620 HANDBOOK OF OBSTETRICS AND GYNECOLOGY

FIGURE 22-1. Leiomyomas of the uterus.

useful for surgical enucleation. Leiomyomas may be multinodular

and are generally lighter in color than normal myometrium. On

typical cut section, leiomyomas exhibit a whorled or trabeculated

pattern of smooth muscle and fibrous connective tissue in varying

proportions. Microscopically, the myocytes are mature and of uni￾form size, with a characteristic benign appearance. The smooth

muscle cells are arranged in bundles and have interspersed fibrous

tissue in direct relation to the extent of atrophy and degeneration

that has occurred. Telangiectasia or lymphectasia occasionally is

present.

Blood supply is generally through one or two major arteries,

and the tumors tend to outgrow their blood supply with subsequent

degeneration. Of larger leiomyomas, two thirds demonstrate some

degeneration. Acute leiomyoma degeneration is relatively uncom￾mon, but this may be necrotic, hemorrhagic (red degeneration), or

septic. Chronic degeneration may be atrophic, hyaline (65%), cys￾tic, calcific (10%), myxomatous (15%), or fatty. Leiomyosarcomas

occur in
0.1%–0.5% of patients with leiomyomas. However, it is

not known if they arise from the leiomyomas.

CLINICAL FINDINGS

Symptoms and Signs

The majority (about two thirds) of women with leiomyomas are

asymptomatic. When symptoms occur, they depend on the number,

size, location, situation, and status (usually vascular supply) of the

tumor(s). Gynecologic symptoms most commonly are abnormal

uterine bleeding, pressure effects, pain, and infertility. Abnormal

uterine bleeding is encountered in
30% of patients with uterine

leiomyomas. Menorrhagia is the most common abnormal uterine

bleeding pattern, and although any pattern is possible, premenstrual

spotting and prolonged light flow after menses often occur. Iron de￾ficiency anemia commonly occurs as a result of the heavier men￾strual blood loss. Rarely, a secondary polycythemia due to increased

erythropoietin occurs with leiomyomas. The cause of this mecha￾nism is uncertain.

The gynecologic symptoms resulting from leiomyomas exert￾ing pressure are variable but most commonly include enlarging ab￾dominal girth, pelvic fullness or heaviness, urinary frequency (from

bladder impingement), and ureteral obstruction. Much less com￾monly encountered are large tumors, causing pelvic congestion with

lower extremity edema or constipation. Parasitic tumors may cause

intestinal obstruction. Cervical tumors may lead to leukorrhea, vagi￾nal bleeding, dyspareunia, or infertility.

CHAPTER 22

DISEASES OF THE UTERUS 621