Consultant, Medical Oncology, Fortis Flt. Lt. Rajan Dhall Hospital, Vasant Kunj, New Delhi
Part 3 of 13 in From Detection to Recovery: Navigating the Future of Cancer Care
From Suspicion to Diagnosis: Blood Tests and Imaging Explained
September 6, 2026
Once a symptom raises suspicion of cancer, the workup follows a fairly predictable sequence of blood tests and imaging, each chosen for a specific reason rather than ordered as a blanket panel, as Dr. Nithin S.G. explained in his masterclass on cancer care.
What Blood Tests Reveal
Most cancer patients develop some degree of anaemia, since a cancer's hypermetabolic state consumes iron faster than the body can replace it. Blood cancers specifically show an abnormal platelet count and an abnormal white cell count, either raised or lowered, and a peripheral smear can reveal abnormal cells called blasts in acute leukaemias. Liver function tests flag possible liver metastasis, kidney function tests matter both for detecting kidney involvement and for planning treatment, and serum LDH rises specifically in lymphomas and in any rapidly proliferating cancer.
Choosing the Right Scan
A breast lump warrants mammography as the first step. Abdominal pain, weight loss or blood in the stool warrants an ultrasound. Beyond that, a contrast-enhanced CT scan, never a plain CT, is the default choice for most solid cancers. A suspected liver mass needs a specific triple-phase contrast CT alongside an AFP blood test; together, in a patient with an already cirrhotic liver or hepatitis B or C, these can confirm liver cancer without any biopsy at all. MRI is reserved for specific situations: suspected brain tumours, uterine cancer, rectal cancer, bladder cancer, prostate cancer, or planning surgery for a tongue or mouth cancer.
The Role of PET-CT
A whole-body FDG PET-CT scan is now used for most cancer patients, both to detect disease and to stage it in one pass. Its limitation is specificity: it lights up any area of high metabolic activity, which includes infections such as tuberculosis, not only cancer. Two exceptions are more specific: a gallium-68 PSMA PET scan for prostate cancer, and a DOTA PET scan for neuroendocrine tumours. Outside those two, a positive PET-CT should always be read alongside the patient's symptoms and other findings rather than treated as a diagnosis on its own.
← When to Suspect Cancer: A Symptom Checklist by Cancer Type | Series index | Why Biopsy Beats FNAC in Cancer Diagnosis →
This article is based on a Jivo Masterclass session conducted by Dr. Nithin S.G., Consultant, Medical Oncology, Fortis Flt. Lt. Rajan Dhall Hospital, Vasant Kunj, New Delhi. The article has been summarised with the assistance of an AI tool from the original masterclass recording. Watch the full Masterclass recording
This guide is based on a live Jivo Masterclass: Dr. Nithin S.G. taught doctors across Africa on May 11, 2025.
FROM THE LIVE Q&A
Dr. Isaia
How effective is immunotherapy compared to other cancer medications?
Dr. Nithin S.G.
Immunotherapy is highly effective and carries far fewer side effects than standard chemotherapy. In cancers with a large initial tumour burden, such as lung cancer, it is usually combined with chemotherapy at first, since immunotherapy alone takes time to bring a heavy disease burden under control. Once the disease responds, treatment continues on immunotherapy alone to maintain that response.
Frequently Asked Questions
What specific investigation should be used to diagnose testicular cancer?▼
Any scrotal swelling should first be evaluated with ultrasound, which will show a testicular mass or enlargement, but there is no test that gives a confirmed diagnosis before surgery, that only comes after radical orchiectomy. Of 100 patients presenting with a testicular swelling, roughly 80 to 90 percent will have cancer and about 10 percent tuberculosis, so for the large majority a biopsy is avoided, since it risks spreading the cancer, in favour of going directly to orchiectomy. Tumour markers such as AFP and beta-hCG, elevated in seminoma and yolk-sac tumours, can support the ultrasound finding, but the standard recommendation regardless of marker levels is orchiectomy rather than biopsy.
How specific is PSA for prostate cancer, given a case where PSA was over 100 but the biopsy showed only BPH?▼
PSA is not specific for prostate cancer at all, no tumour marker is specific for any single cancer. An elevated PSA in a patient with a prostatic mass could reflect BPH or cancer, and can rise even after a digital rectal exam or ejaculation. Very high values, such as over 100, are more suggestive of cancer, so if PSA is extremely elevated yet the biopsy shows only BPH, the biopsy may simply have missed the cancerous core, which does happen. In such suspicious cases, a gallium-68 PSMA PET scan, highly specific for prostate cancer, can help confirm or rule out malignancy before treating for BPH alone.
Should breast cancer be diagnosed with a core biopsy or an excisional biopsy?▼
Core needle biopsy is sufficient for breast cancer, and there is no need for excisional biopsy in most cases. For a small tumour such as a fibroadenoma, excisional biopsy is an option, but core needle biopsy is equally effective, and if the mass proves benign, surgery can be avoided altogether.
Can precision oncology or targeted therapy offer a drug for uterine fibroids, since they are so common?▼
Unfortunately there is no specific genetic mutation identified for uterine fibroids and no targeted drug role for them, since fibroids are benign tumours, not cancers. Treatment options remain limited to hormonal therapy or surgery.
What is your opinion on targeted therapy for advanced cancer patients with a poor performance status?▼
Targeted therapy's main advantage is that it is mostly oral medication without the classic side effects of chemotherapy, so it remains a reasonable option even in poor performance status, though this depends on the specific drug and its side-effect profile rather than being a blanket rule. Two cases illustrate this: a metastatic lung cancer patient with brain metastases who was bedridden with severe headache and vomiting, and a metastatic breast cancer patient with cerebellar metastasis causing incoordination, both showed marked improvement on targeted therapy despite their poor baseline state. Overall, more patients in poor performance status can be treated with targeted therapy than with chemotherapy, since chemotherapy is often not feasible in a very poor clinical state.
Why does a plain CT scan get avoided in cancer diagnosis?▼
A contrast-enhanced CT scan is the standard for most solid cancers; a plain scan without contrast is not used for cancer diagnosis.
When is MRI preferred over CT for a suspected cancer?▼
MRI is reserved for suspected brain tumours, uterine cancer, rectal cancer, bladder cancer, prostate cancer, or when planning surgery for a tongue or mouth cancer.
Is a positive PET-CT scan proof of cancer?▼
No. PET-CT is highly sensitive but not specific to cancer; it can also light up infections such as tuberculosis, so a positive scan needs to be read alongside the patient's symptoms and other test results.
In This Series: From Detection to Recovery: Navigating the Future of Cancer Care
- 1.From Detection to Recovery
- 2.When to Suspect Cancer: A Symptom Checklist by Cancer Type
- 3.From Suspicion to Diagnosis: Blood Tests and Imaging Explained
- 4.Why Biopsy Beats FNAC in Cancer Diagnosis
- 5.Tumour Markers: What They Can and Cannot Tell You
- 6.Cancer Staging and Why It Decides the Treatment Plan
- 7.Precision Oncology: How Genetic Testing Is Changing Cancer Treatment
- 8.Immunotherapy: Retraining the Immune System to Fight Cancer
- 9.Breast Cancer: Subtypes, Diagnosis and Newer Targeted Treatments
- 10.Targeted Therapy for Advanced Cancer Patients with Poor Performance Status
- 11.Testicular Cancer, Prostate Cancer and PSA: Working Up Common Urologic Presentations
- 12.Liquid Biopsy: A Newer, Less Invasive Way to Detect and Monitor Cancer
- 13.Uterine Fibroids Are Not Cancer: Why Targeted Therapy Doesn't Apply