Difficulties with diagnosis of malignancies in pregnancy

• Tumour markers such as HE4, CA 19-9 and carcino-embryonic antigen (CEA) are not elevated by pregnancy.
• [Fluorine-18]fluoro-D-glucose (18F-FGD) positron emission tomography (PET) scans seem safe during pregnancy.
• Gadolinium-enhanced magnetic resonance imaging (MRI) is acquired less for staging due to diffusion-weighted imaging (DWI).
• DWI has close correlations with surgical-based staging for peritoneal disease spread.
• Pregnancy causes tumour-like histopathology of several tissues.

Diagnosis and staging of cancer during pregnancy may be difficult due to overlap in physical signs, uncertainties on safety and accuracy of diagnostic tests and histopathology in pregnant women. Tumour markers should be used with caution due to pregnancy-induced elevation. Ionizing imaging and staging techniques such as computed tomography (CT) or positron emission tomography (PET) scans and sentinel node procedures are safe during pregnancy when fetal radiation threshold of 100 mGy is maintained. Ionizing imaging techniques can increasingly be avoided with the technical devolvement of non-ionizing techniques such as magnetic resonance imaging (MRI), including whole body MRI and diffusion-weighted imaging, which hold potentially great opportunities for the diagnostic management of pregnant cancer patients. Pathological evaluation and establishing a diagnosis of malignancy can be difficult in pregnant women, and a note to the pathologist of the pregnant status is essential for accurate diagnosis. This chapter will give an overview of possibilities and difficulties in diagnosing pregnant women with cancer.