The following classification for gestational trophoblastic tumours is based on that of FIGO adopted in 1992 and updated in 2001 (Ngan HYS, Bender H, Benedet JL, Jones H, Montrucolli GC, Pecorelli S (FIGO Committee on Gynecologic Oncology). Gestational trophoblastic neoplasia. Int J Gynecol Obstet 2002; 77:285–287).

The definitions of T and M categories correspond the FIGO stages. Both systems are included for comparison. In contrast to other sites, an N (regional lymph node) classification does not apply to these tumours. A prognostic scoring index, which is based on factors other than the anatomic extent of the disease, is used to assign cases to high risk and low risk categories, and these categories are used in stage grouping.

Rules for Classification

The classification applies to choriocarcinoma (9100/3), invasive hydatidiform mole (9100/1), and placental site trophoblastic tumour (9104/1). Placental site tumours should be reported separately. Histological confirmation is not required if the human chorionic gonadotropin (ßhCG) level is abnormally elevated. History of prior chemotherapy for this disease should be noted.

TNM Clinical Classification

T – Primary Tumour/M – Distant Metastasis

TNM Categories	FIGO Stages*	Definition
TX		Primary tumour cannot be assessed
T0		No evidence of primary tumour
T1	I	Tumour confined to the uterus (Fig. 461)
T2	II	Tumour extends to other genital structures: vagina, ovary, broad ligament, fallopian tube(s), by direct extension or metastasis (Fig. 462)
M1a	III	Metastasis to lung(s)
M1b	IV	Other distant metastasis

Note
*Stage I to IV are subdivided into A and B according to the prognostic score.