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What is Choriocarcinoma and explain in detail?
Choriocarcinoma is a malignant, trophoblastic cancer, usually of the placenta. It is characterized by early hematogenous spread to the lungs. It belongs to the malignant end of the spectrum in gestational trophoblastic disease (GTD). It is also classified as a germ cell tumor and may arise in the testis or ovary.

Signs and symptoms
increased quantitative chorionic gonadotropin (the "pregnancy hormone") levels
vaginal bleeding
shortness of breath
hemoptysis (coughing up blood)
chest pain
chest X-ray shows multiple infiltrates of various shapes in both lungs
presents in males as a testicular cancer, sometimes with skin hyperpigmentation (from excess chorionic gonadotropin cross reacting with the alpha MSH receptor), gynecomastia, and weight loss (from excess chorionic gonadotropin cross reacting with the LH, FSH, and TSH receptor) in males
can present with decreased thyroid-stimulating hormone (TSH) due to hyperthyroidism.

Cause
Choriocarcinoma of the placenta during pregnancy is preceded by:

hydatidiform mole (50% of cases)
spontaneous abortion (20% of cases)
ectopic pregnancy (2% of cases)
normal term pregnancy (20–30% of cases)
hyperemesis gravidarumRarely, choriocarcinoma occurs in primary locations other than the placenta;  very rarely, it occurs in testicles. Although trophoblastic components are common components of mixed germ cell tumors, pure choriocarcinoma of the adult testis is rare. Pure choriocarcinoma of the testis represents the most aggressive pathologic variant of germ cell tumors in adults, characteristically with early hematogenous and lymphatic metastatic spread