Ectopic pregnancies are the main sources of pregnancy-related morbidity and mortality in the first trimester. They are usually located in the ampullary part of the fallopian tube and the incidence increases in the setting of assisted reproductive techniques, older age at the time of the first pregnancy, and prior adnexal procedures. The clinical aspects and diagnostic challenges of an ectopic pregnancy for the pathologist are to be outlined. A review of the relevant literature was performed. Proof of gestational tissue is of utmost importance in the pathological-anatomical evaluation of an ectopic pregnancy. A complete evaluation of the specimen of a presumed tubal abruption or after milking out should be performed. Abnormal placentations (blighted ovum, embryonal molar pregnancy) as well as gestational trophoblastic disease (GTD, e.g., partial/complete molar pregnancy, choriocarcinoma) can occur in the setting of an ectopic pregnancy. Caution must be taken to differentiate a trophoblast hyperplasia secondary to the tubal microenvironment from GTD. p57 immunohistochemistry can help exclude a molar pregnancy. Only 50% of ectopic pregnancies are associated with tubal pathologies (e. g. inflammation, tubal adhesions). Chorionic villi and trophoblast epithelia can demonstrate regressive changes after prior methotrexate treatment. Rarely, immunohistochemistry with GATA-3, p63, β‑HCG, PAX-8, and WT-1 can be used in the differential diagnosis of trophoblastic epithelium. Ectopic pregnancies are associated with significant morbidity and mortality. A thorough evaluation of the specimen can help guide management and follow-up.
Keywords: Choriocarcinoma; Ectopic pregnancy; Fallopian tubes; Gestational trophoblastic disease; Hydatidiform mole.