Due to the low penetration depth of THz waves, research in biomedical THz imaging has been primarily focused on the reflection-mode spectroscopy for the diagnosis of various types of cancer (breast, skin, cervical and colon) as well as the classification of skin burns. However, alternative techniques have been around for many decades. For instance, X-rays provide an inexpensive and high-resolution imaging methodology with excellent tissue penetration. Also, MRI screening offers non-ionizing, high-resolution tomography, and microscopic imaging (biopsy) is a benchmark when it comes to diagnosis reliability. Nevertheless, one of the biggest problems in medical imaging is to combine the microscopic and macroscopic imaging to define cancerous tissue margins more reliably. THz imaging cannot match microscopy in image resolution; however, it can provide unique macroscopic information such as tissue permittivity and absorption. Perhaps more importantly, unlike X-rays, THz waves are non-ionizing and thus considered safe for extended exposure times.