A primary tumor is one that has started in the brain, as opposed to a metastatic tumor, which is one that has spread to the brain from another area of the body. The incidence of metastatic tumors is approximately four times greater than primary tumors. Tumors may or may not be symptomatic: some tumors are discovered because the patient has symptoms, others show up incidentally on an imaging scan, or at an autopsy.Grading of the tumors of the central nervous system commonly occurs on a 4-point scale (I-IV) created by the World Health Organization in 1993. Grade I tumors are the least severe and commonly associated with long-term survival, with severity and prognosis worsening as the grade increases. Low-grade tumors are often benign, while higher grades are aggressively malignant and/or metastatic. Other grading scales do exist, many based upon the same criteria as the WHO scale and graded from I-IV. Primary
The most common primary brain tumors are:
Gliomas (50.4%)
Meningiomas (20.8%)
Pituitary adenomas (15%)
Nerve sheath tumors (10%)These common tumors can also be organized according to tissue of origin as shown below:

Secondary
Secondary tumors of the brain are metastatic and have invaded the brain from cancers originating in other organs. This means that a cancerous neoplasm has developed in another organ elsewhere in the body and that cancer cells have leaked from that primary tumor and then entered the lymphatic system and blood vessels. They then circulate through the bloodstream, and are deposited in the brain. There, these cells continue growing and dividing, becoming another invasive neoplasm of primary cancers tissue.
An abdominal pregnancy is a rare type of ectopic pregnancy where the embryo or fetus is growing and developing outside the womb in the abdomen, but not in the Fallopian tube (usual location), ovary or broad ligament.Because tubal, ovarian and broad ligament pregnancies are as difficult to diagnose and treat as abdominal pregnancies, their exclusion from the most common definition of abdominal pregnancy has been debated.Others—in the minority—are of the view that abdominal pregnancy should be defined by a placenta implanted into the peritoneum. Signs and symptoms
Symptoms may include abdominal pain or vaginal bleeding during pregnancy. As this is nonspecific in areas where ultrasound is not available the diagnosis was often only discovered during surgery to investigate the abnormal symptoms. They are typically diagnosed later in the developing world than the developed. In about half of cases from a center in the developing world the diagnosis was initially missed.It is a dangerous condition as there can be bleeding into the abdomen that results in low blood pressure and can be fatal. Other causes of death in women with an abdominal pregnancy include anemia, pulmonary embolus, coagulopathy, and infection. Risk factors
Risk factors are similar to tubal pregnancy with sexually transmitted disease playing a major role; however about half of those with ectopic pregnancy have no known risk factors (which include damage to the Fallopian tubes from previous surgery or from previous ectopic pregnancy, and tobacco smoking).