Cancer association with pregnancy (CAP) is defined as cancer diagnosed from the 1st day of childbearing to 1 year postpartum. Malignant disease in pregnancy is rare, 1:1000 pregnancies, but it represents an important therapeutic and ethical problem for both, the patient and the physician. The most important goals in curing are—treating the patient with the optimal anticancer regimen as soon as possible in order to preserve the mother's health, without harming the developing fetus. Until recently, the pregnancy had to be either terminated or cancer treatment delayed until after the birth. Nowadays, state-of-art treatment should be provided for this vulnerable population to preserve maternal and fetal prognosis. When suspicion of malignant disease in pregnancy is grounded, it is necessary to prove the same. It is recommended to apply standard methods, if possible. With some malignant tumors, some protocols for establishing diagnosis are changing sensitivity and specificity in pregnancy. Ultrasound examination is a method of choice for the breast, abdomen, and pelvis. If necessary, chest X-ray and mammography can be done safely with abdominal shielding. Magnetic resonance imaging (MRI) may be conducted if there is any unclarity in the analysis or suspicion of brain or bone metastasis. The main challenge in managing cancer in pregnancy is treating the patient with an optimal anticancer regimen without harming the developing fetus. Cancer during pregnancy is associated with a significantly increased risk of planned preterm birth, induction of labor, and a cesarean section. Women with CAP need psychological support during the pregnancy and after delivery.