Ultrasound screening
Ultrasound, also referred to as sonography, is a technique in which high-frequency sound waves, inaudible for humans, are bounced off tissues and internal organs. The echoes generated produce a picture known as a sonogram. This form of imaging is commonly used to distinguish between solid tumours and cysts. An ultrasound is sometimes also used to examine lumps that are otherwise difficult to see.
Ultrasound can also be used as part of other diagnostic procedures, such as needle biopsies (the removal of cancer tissue, or fluid, through the use of needles to be analysed by a laboratory), if there is reason to suspect cancer.
Although ultrasound is not suitable for detecting very early signs of cancer, regular ultrasound screening is recommended, twice a year, from the age of 5.
Price per ultrasound screening of the chest: between 250.- and 500.- Sfr. 
(Resource: Animal Oncology and Imaging Center, Hünenberg, Switzerland)

Blood analysis:
A blood analysis consisting of hemogram (white blood cells, red blood cells and platelets) and a biochemistry analysis (liver, kidney enzymes, proteins, glucose and electrolytes) is recommended in all cancer patients. On top, often an urine-analysis is required, too. Although these tests are not specific for the diagnosis of cancer, they can contribute to a definitive diagnosis. Tumors often have secondary effects on the blood, for example can cause anaemia, low platelet numbers or elevate liver or kidney enzymes or induce electrolyte imbalances. Dogs may have other illnesses besides the tumor which is another reason for a thorough initial screening.
Price per analysis: approx 80.– Sfr.
(Resource: Animal Oncology and Imaging Center, Hünenberg, Switzerland)

Chest radiography (x-ray)
Either conventional x-ray or digital x-ray which uses computerized images. The main purpose of radiography is to document the presence of the underlying anatomy, and in other cases to see functional changes associated with the disease. Chest (thoracic) radiography is inexpensive and quickly done on an awake animal (doesn’t need anaesthesia), but it is less reliable for the visualization of lung metastases compared with the more expensive and also technically more demanding computer tomography which is carried out under general anaesthesia. But both techniques are poor in distinguishing the underlying pathology that distinguishes a benign lesion like a granuloma from a malign metastatic growth. An absolute diagnosis can only be obtained by taking a biopsy.
Price per screening by x-ray: approx.. 200.– Sfr.
(Resource: Animal Oncology and Imaging Center, Hünenberg, Switzerland) 

CT – Computertomography
CT is the dominant diagnostic tool for staging (=evalutating the size of a tumor = stage) and also evaluating the possible response to future therapy. CT is conducted with an x-ray tube and a detector to obtain planar or spiral “slices” of the patient’s anatomy. The information obtained is reconstructed by a computer to give hundreds of images that can also be further reconstructed to make three dimensional (3D) images. Those are very helpful for planning surgeries or radiation therapy of tumors. CT is also excellent for evaluating a patient’s pulmonary (lung) metastases in less than a minute. This method requires that the dog is immobilized with anaesthesia. The detail of a CT is further enhanced by the use of a contrast agent which is injected intravenously. CT gives also superior results compared to normal x-ray for imaging of nasal cavity, skull, jaw, pelvis and vertebral bones. In addition, lymph nodes, especially in the head and neck region, can be better visualized and evaluated for metastatic diseases. CT is also superior to radiography to screen for pulmonary metastases.
Price approximately 1000 Sfr
(Resource: Animal Oncology and Imaging Center, Hünenberg, Switzerland)

MRI (magnetic resonance imaging)
MRI is the creation of detailed pictures of areas inside the body through the use of a magnet; this form of imaging does not use radiation. An MRI of an internal organ is conducted by placing the patient on a scanning table. The table is then moved into a tube-like machine that contains a magnet. The first series of picture is then taken, after which the patient sometimes receives a contrast agent, to improve the visibility of a tumour. The entire session may take about an hour and dogs have to be given a general anaesthesia. MRI is excellent about providing information on soft tissue structures, including and especially the central nervous system (brain and nerves).
Price per screening: approx.. 1500.– Sfr.
(Resource: Animal Oncology and Imaging Center, Hünenberg, Switzerland)

PET scan (positron emission tomography):
A PET (positron emission tomography) scan is a computerised image of chemical changes taking place in human tissue. Patients are given an injection of a combination of sugar and a small amount of radioactive material. This radioactive sugar helps in locating a tumour, because cancer cells absorb sugar faster than other tissues in the body. After the radioactive substance has been injected, the patient lies still on a table for approx. 45 minutes while he is moved through the PET scanner 6 to 7 times. This time frame allows the drug to circulate in the body, and if a tumour is present, the sugar will accumulate in it. PET scans are more accurate in detecting larger and/or aggressive tumours than they are in locating small and/or less aggressive ones.
PET scans are widely used in human oncologic patients, but is hardly available for pets.
This will for sure change in the near future. 

Early stages

• loss of appetite
• weight loss
• lethargy
• exercise intolerance, partial paralysis (becoming partially lame) 
• vomiting/diarrhea
• pale tongue and gums
• distended abdomen
• increased respiratory rate and effort 

Later stages

• early-stage symptoms persist
• refusal to eat
• reclusive behavior
• distended abdomen
• mental sluggishness (depressive)
• difficulty breathing
• panting, gasping for breath
• black, tarry stool
• sudden collapse
• inability to rise
• pale tongue and gum
• loss of blood from any body orifice (anus, vagina, mouth, eyes, ears…)

Crisis
Immediate veterinary assistance needed regardless of the disease!

• Difficulty breathing
• Refusing to eat or drink
• Prolonged seizures
• Uncontrollable vomiting/diarrhea
• Black, tarry stool
• Difficulty in urinating
• Blood in the urine
• Sudden collapse
• Profuse bleeding — internal or external
• Crying/whining from pain, for example when taken into the arms

It should be noted that most animals will instinctually hide their pain. Therefore, vocalization of any sort that is out of the ordinary for your pet may indicate that their pain and anxiety has become too much for them to bear. If your pet vocalizes due to pain or anxiety, please consult with your attending veterinarian immediately.

Resources and further reading:
http://www.petmd.com/blogs/fullyvetted/2012/july/hemangiosarcoma_in_dogs-26511