Choriocarcinoma is a malignant tumor of the trophoblastic epithelium. Uterine muscle and blood vessels are invaded with areas of hemorrhage and necrosis. Columns and sheets of trophoblastic tissue invade normal tissues and spread to distant sites, the most common of which are lungs, brain, liver, pelvis, vagina, spleen, intestines, and kidney. Most choriocarcinomas have an aneuploid karyotype, and about three-quarters of them contain a Y chromosome. Most follow an HM pregnancy, spontaneous abortion, or ectopic pregnancy; but, about one-quarter of them are preceded by a full-term pregnancy. Nearly all GTDs that are preceded by nonmolar pregnancies are choriocarcinomas; the rare exceptions generally are PSTTs.
PSTT disease is the result of a very rare tumor arising from the placental implantation site and resembles an exaggerated form of syncytial endometritis. Trophoblastic cells infiltrate the myometrium, and there is vascular invasion. Human placental lactogen is present in the tumor cells, whereas immunoperoxidase staining for human chorionic gonadotropin (hCG) is positive in only scattered cells, and elevations in serum hCG are relatively low compared with the marked elevations seen in choriocarcinoma. hCG is not a reliable marker of tumor volume.[1,2] PSTTs have much lower growth rates than choriocarcinoma, and presentation after a full-term pregnancy is often delayed by months or years. They are generally resistant to chemotherapy. Therefore, hysterectomy is the standard primary treatment if the tumor is confined to the uterus. However, about 35% of PSTTs have distant metastases at diagnosis.[2,3] Common sites of metastasis include the lungs, pelvis, and lymph nodes. Central nervous system, renal, and liver metastases have also been observed.
ETT is an extremely rare gestational trophoblastic tumor.[4,5] Although originally termed atypical choriocarcinoma, it appears to be less aggressive than choriocarcinoma and is now regarded as a distinct entity. Pathologically, it has a monomorphic cellular pattern of epithelioid cells and may resemble squamous cell cancer of the cervix when arising in the cervical canal. Its clinical behavior appears to be closer to that of PSTT than to choriocarcinoma. It has a spectrum of clinical behavior from benign to malignant. About one-third of patients present with metastases, usually in the lungs.
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- Feltmate CM, Genest DR, Goldstein DP, et al.: Advances in the understanding of placental site trophoblastic tumor. J Reprod Med 47 (5): 337-41, 2002.
- Schmid P, Nagai Y, Agarwal R, et al.: Prognostic markers and long-term outcome of placental-site trophoblastic tumours: a retrospective observational study. Lancet 374 (9683): 48-55, 2009.
- Shih IM, Kurman RJ: Epithelioid trophoblastic tumor: a neoplasm distinct from choriocarcinoma and placental site trophoblastic tumor simulating carcinoma. Am J Surg Pathol 22 (11): 1393-403, 1998.
- Palmer JE, Macdonald M, Wells M, et al.: Epithelioid trophoblastic tumor: a review of the literature. J Reprod Med 53 (7): 465-75, 2008.