Partial hydatidiform mole and invasive mole (human)

(A) Macroscopy: The partial mole (1) occupies a large part of the placenta and is distinct from the normal chorionic plate where the umbilical cord (2) inserts eccentrically with branches of the umbilical vessels. The inset shows a circumscript area with swollen transparent grape-like vesicles (chorionic villi) of varying diameter. (B): Macroscopy: Enlarged uterus (3) with an invasive mole (mole destruens or chorioadenoma destruens or previously deciduoma malignum) as a large circumscript area (4) within the wall. Background: Gestational trophoblastic diseases (GTD) consist of a group of disorders characterized by abnormal trophoblast proliferation during pregnancy. They include a non-cancerous type (e.g. hydatidiform mole) and cancerous types (e.g. invasive mole or chorioadenoma and choriocarcinoma). The non-cancerous GTD or hydatidiform mole (mola hydatidosa) is an abnormal gravidity characterized by: (1) absence c.q.limited number of fetal vessels within the chorionic vili; (2) trophoblastic proliferation of chorionic villi; (3) hydropic degeneration; (4) no presence of embryo or fetus. Microscopically the proliferation of syncytiotroblast and cytotrophoblast is a characteristic hallmark of the hydatidiform mole. The cellular proliferation results in increased blood hCG (human Choriogonadotrophin) as well as urinary excretion of hCG Progression to invasive mole (or mole destruens, proliferans or chorioadenoma destruens) and/or choriocarcinoma might occur in 5-10% of all patients with a hydatidiform mole. This process could be monitored by high levels of hCG in serum for months due to persisting trophoblast proliferation, even after terminating the gravid cycle by abortion or vacuum aspiration. In contrast to a complete mole without any traces of embryos in a partial mole only part of the chorionic villi abnormalizes and embryonal structures appear to be present that usually abort within a few months. In 5-10 % of moles they penetrate through the uterine wall and myometrial vessels may be breached. This type of mole represents a molar version of a placenta increta where the normal placental villi penetrate deeply into the myometrium. This type of GTD might grow completely through the myometrium with the result of bleeding that can be life threatening, In ca. 15% of the cases the proliferating cells metastasize to different organs, most often to the lungs. (By courtesy of G. P. Vooijs MD, PhD, former Head of the Department of Pathology, and the Museum of Anatomy and Pathology, University Medical Center, St. Radboud University, Nijmegen, The Netherlands)