Pathology:

a) Origin: 96% of fibroids occur in uterine body and only 4% occur in the cervix. Rarely fibroids develop in ovarian ligament, uterosacral ligament, or smooth muscle fibres in between the two layers of broad ligament.

b) Varieties:

1‑ Interstitial: Situated in muscle wall of the uterus.

2‑Submucus: when the tumour projects into the uterine cavity. It rnay become pedunculated forming a submucous fibroid polyp.

3‑Subserous: The tumour projects to the outer surface of the uterus and becomes covered with peritoneum. It may be pedunculated. Occasionally, they attach themselves to the surrounding structures from which they obtain blood supply ( Parasitic fibroid).

4‑ Rare types:

A) Intravenous leiomyomatosis : Characterized by multiple worm‑like cords in the myometrial and parametrial veins that occasionally may extend into the IVC and right side of the heart .

B) Benign metastasizing leiomyoma : Characterized by multiple small histologically benign pulmonary leimyomatous nodules

C) Gross anpearance:

-Number: It may be single (as in cervical myoma) or multiple

-Size: variable ( small seedling to large fibroid filling the abdominal cavity)

-Shape: usually spherical .

-Consistency: usually firm in consistency but may become soft during pregnancy, with hyaline and cystic degeneration. It may become hard with calcification.

-Capsule: Myomas has no capsule of its own but surrounded by false capsule made of the compressed surrounding muscle layer.

-Cut section: is paler than the surrounding, showing whorly appearance of intermingling smooth muscles and fibrous tissue

-Blood supply:

Fibroids receive their blood supply from vessels originating in the capsule and passing inwards, while fibroid polypi receive their blood supply from vessels in the pedicle, this explains the following:

A- Hyaline degeneration starts in the center ( poor blood supply).

II‑ Calcium deposition starts at the periphery.

III‑Necrosis occurs at the tip of fibroid polyp.

d) Microscopic picture:

‑Bundles of smooth muscle cells which are coloured yellow with Van Geison stain The smooth muscle cell is a long spindle shaped cell with excess esinophilic cytoplasm. The nucleus is relatively shorter with blunt ends. These are intermingled with

‑Bundles of fibrous tissue composed of fibroblasts and collagen fibres which stain pink with Van Geison stain. Fibroblasts are fusiform cells with scanty basophilic cytoplasm and large nuclei with tapering ends filling most of the cytoplasm.

Pathological changes:

I‑Degenerative changes:

1‑ Atrophy: It occurs after menopause due to decreased blood supply and estrogen. It may occur during puerperium following rapid enlargement during pregnancy.

2‑ Necrosis: It results from cutting of the blood supply e.g. a complication of radiotherapy

3‑ Hyaline degeneration: It is the most common type of degeneration occurring at the center of the tumour due to poor blood supply. The whorly appearance is lost and become replaced by homogenous structurless hyaline material which stains pink with eosin. Clinically, the tumour becomes soft and the patient may feel dull pain.

4‑ Cystic degenerafion: It may occur due to:

a)Liquefaction of hyaline material leading to formation of pseudocysts.

b)Lymphangiectasis and telangiectasis leading to formation of true cysts lined with endothelium.

The tumour becomes soft cystic and may be mistaken for a pregnant uterus.

5‑ Fatty degeneration: There is deposition of fat in tumour cells or in stromal histiocytes which become yellowish. It is a precursor of calcification.

6- Calcification: Calcium salts are deposited at the periphery of the tumour along the course of blood vessels. The tumour becomes hard and may give an X‑ ray shadow (womb stone).

7‑ Red (carneous) degenerafion:

Definition: It is an incomplete necrosis ( Necrobiosis) from which the tumouris capable of recovery. It commonly occurs during pregnancy.

Pathogenesis: Thrombosis occurs in the vessels of the capsule leading to ischemia of a part of the tumour. The ischemic part produces a lipoid toxin that leads to intravascular hemolysis so that Hb diffuses out and the tumour becomes reddish. The frequency of necrobiosis during pregnancy can be attributed to: a) Congestion, b) Increased fibrinogen, and c) Kinking of blood vessels as a result of rapid growth.

Pathology: The tumour becomes soft, red in color which darkens on exposure to air due to formation of methemoglobin. The freshly cut tumour has a fishy odor due to

  secondary infection. Microscopically there is thrombosis of the blood vessels with hemoglobin pigments between the muscle fibers

Clinically: there is sudden severe abdominal pain localized over the tumour. There is fever, vomiting and leucocytosis. On palpation, the tumour is tense and tender

Treatment:

One. Conservative: During pregnancy, treatment is mainly conservative consisting of rest, sedatives analgesics and fluids.

Two. Operative: ‑ In few cases if the pain is severe with failure of medical treatment or if the diagnosis is doubtful, laparotomy is performed and only the affected tumour is removed.

II-Malignant change:

Incidence: Malignant transformation into leiomyosarcoma is rare occurring only in 0.1% of cases.

Macroscopically, the tumor infiltrates the capsule with loss of the whorly appearance and areas of hemorrhage and necrosis.

Microscopically, it is round or spindle cell sarcoma. There are more than 10 mitoses/HPF. Clinically: Sarcomatous change is suspected in the following conditions: 1‑ Rapid growth. 2‑ Postmenopausal growth. 3‑ Postmenopausal bleeding. 4‑ Rapid recurrence after removal.

III-Vascular changes:

One- Congestion: Due to torsion of pedunculated subserous fibroid.

Two- Edema: Due to congestion, infection, impaction or torsion.

Three- Lymphangiectasis and telangiectasis. ~

IV- Infection: It may occur in the following conditions:

1- Submucus fibroid after curettage or abortion.

2- Subserous fibroid from a neighboring bowel or appendix.

3‑Tip of a fibroid polyp due to poor blood supply.

V)Complications:

I‑Torsion of pedunculated subserous fibroid.

2- Rupture of a surface vein of subserous fibroid leading to internal hemorrhage

3- Infection.

4- Red degeneration.

5- Malignant change.

6- Chronic inversion in case of a large fundal fibroid polyp.

7- Impaction ( incarceration) especially in case of cervical or posterior wall subserous fibroid.