32 Gestational Trophoblastic Tumors 32

32 Gestational Trophoblastic Tumors

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SUMMARY OF CHANGES

• Gestational trophoblastic tumors are effectively treated with chemotherapy even when widely metastatic so that traditional anatomic staging parameters do not adequately provide different diagnostic categories. For this reason, although the anatomic categories are preserved, a scoring system of other nonanatomic risk factors has been added. This risk factor score provides the basis for substag- ing patients into A (low risk, score of 7 or less) or B (high risk, score of 8 or greater).

• The “Risk Factors” portion of the stage grouping has been revised to reflect the new scoring system.

C58.9 Placenta

INTRODUCTION

Gestational trophoblastic tumors are uncommon (1 in 1,000 pregnancies) malignancies that arise from the placenta. Usually as a result of a genetic acci- dent in the developing egg, the maternal chromosomes are lost, and the pater- nal chromosomes duplicate (46xxx). The resulting tumor is known as a complete hydatidiform mole: there are no fetal parts; the tumor is composed of dilated, avascular, “grape-like” vesicles that may grow as large as, or larger than, the normal pregnancy it replaces. There is obviously no heartbeat detected, and the patient may have vaginal bleeding similar to a miscarriage. Many times, the diag- nosis is not made until a dilatation and curettage is done and the tissue is exam- ined pathologically. In some patients, fetal parts will be found in association with mild proliferative trophoblastic (placental) tissues. Such patients have a partial hydatidiform mole, which has a 69xxx or 69xxy chromosomal complement resulting from twice the normal number of paternal chromosomes. Both of these tumors usually follow a benign course, resolving completely after evacua- tion by the dilatation and suction or curettage, but approximately 20% of com- plete moles and 5% of partial moles persist locally or metastasize and thus require chemotherapy.

Much less frequently (about 1 in 20,000 pregnancies in the United States), a highly malignant, rapidly growing metastatic form of gestational tropho- blastic disease called choriocarcinoma is encountered. This solid, anaplastic, avascular, and aggressively proliferative tumor is easily recognized microscopi- cally and may present with symptoms of vaginal bleeding (as with a hydatidi- form mole). However, metastatic lesions may be the first sign of this lesion, which can follow any pregnancy event, including an incomplete abortion or a full-term pregnancy.

The trophoblastic tissue that makes up these tumors produces a serum

tumor marker, beta-human chorionic gonadotrophin ( b-hCG), which is very

helpful in the diagnosis and monitoring of therapy in these patients. Gestational

trophoblastic tumors are very responsive to chemotherapy, with cure rates approaching 100%.

ANATOMY

Because of the responsiveness of this tumor to treatment and the accuracy of the serum marker hCG in reflecting the status of disease, the traditional anatomic staging system used in most solid tumors has little prognostic signif- icance. Trophoblastic tumors not associated with pregnancy (ovarian teratomas) are not included in this classification.

Primary Site. By definition, gestational trophoblastic tumors arise from placental tissue in the uterus. Although most of these tumors are noninvasive and are removed by dilatation and suction evacuation, local invasion of the myometrium can occur. When this is diagnosed on a hysterectomy specimen (rarely done these days), it may be reported as an invasive hydatidiform mole.

Regional Lymph Nodes. Nodal involvement in gestational trophoblastic tumors is rare but has a very poor prognosis when diagnosed. There is no regional designation in the staging of these tumors. Nodal metastases should be classified as metastatic (M1) disease.

Metastatic Sites. This is a highly vascular tumor that results in frequent, wide- spread metastases when these lesions become malignant. The cervix and vagina are common pelvic sites of metastases (T2), and the lungs are often involved by distant metastases (M1a). Other, less frequently encountered metastatic sites include kidney, gastrointestinal tract, and spleen (M1b). The liver and brain are occasionally involved and may harbor metastatic sites that are difficult to treat with chemotherapy.

DEFINITIONS Primary Tumor (T)

TNM* FIGO

Categories Stages

TX Primary tumor cannot be assessed

T0 No evidence of primary tumor

T1 I Disease limited to uterus (Figure 32.1)

T2 II Disease outside of uterus but limited to genital structures (ovary, tube, vagina, broad ligaments) (Figure 32.2) Distant Metastasis (M)

MX Metastasis cannot be assessed

M0 No distant metastasis

M1 Distant metastasis

M1a III Lung metastasis (Figure 32.3)

M1b IV All other distant metastasis (Figure 32.4)

*Note: There is no regional nodal staging for this tumor.

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TNM: T1

TNM: T1

FIGURE 32.1. Two views of T1 (disease confined to the uterus): tumor confined to endometrium (left side of dotted line) and tumor with invasion of myometrium and cervix (right side of dotted line).

TNM: T2

TNM: T2

Ascites, peritoneal washing

FIGURE 32.2. Two views of T2 (disease outside of the uterus but limited to genital

structures): involvement of the vagina (left side of the dotted line), fallopian tube

and ovary as well as the presence of malignant ascites (right side of the dotted

line).

STAGE GROUPING

Stage T M Risk Factors

I T1 M0 Unknown

IA T1 M0 Low risk

IB T1 M0 High risk

II T2 M0 Unknown

IIA T2 M0 Low risk

IIB T2 M0 High risk

III Any T M1a Unknown

IIIA Any T M1a Low risk

IIIB Any T M1a High risk

IV Any T M1b Unknown

IVA Any T M1b Low risk

IVB Any T M1b High risk

M1a

Primary tumor Metastasis

FIGURE 32.3. M1a is defined as metastatic disease to the lung.

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M1b

Metastasis (node)

Metastasis (node)

Metastasis (node)

Metastasis (bone) Primary

tumor

FIGURE 32.4. M1b disease is metastases to all other distant sites.

TABLE 32.1 Prognostic Indicators Scoring Index

Risk Score

Prognostic Factor 0 1 2 4

Age <40 >40

Antecedent pregnancy H. mole Abortion Term pregnancy

Interval months from <4 4–<7 7–12 >12

index pregnancy

Pretreatment hCG <10

≥10

–<10

10

–<10

≥10

(IU/ml)

Largest tumor size <3cm 3–<5cm ≥5cm

including uterus

Site of metastases Lung Spleen, Gastrointestinal Brain, liver

kidney tract

Number of metastases 1–4 5–8 >8

identified

Previous failed Single drug Two or more

chemotherapy drugs

Total Score

Low risk is a score of 7 or less. High risk is a score of 8 or greater.

NOTES

1. See Table 32.1, prognostic indicator section for substage definitions.

2. See Table 32.1, prognostic indicators for substage grouping.