Cancer can be classified differently and in different levels of depth depending on the context. This section will briefly outline a few different classifications of tumors.
Cancer can be separated by malignant or benign tumors. This is a largely unquantifiable term and is used more colloquially. Calling a tumor benign usually means it is not concerning, slow growing, unlikely to metastasize, or perhaps not even a cancer but a small lump caused by something other than genetic mutation. Malignant usually means it could metastasize, or is fast growing/aggressive and must be dealt with. These terms are nuanced and if confused or concerned about a personal case talk to your doctor.
Cancers can be classified by the organ of origin, simply saying breast cancer, lung cancer, etc. However to go slightly more in depth cancers can be classified by the tissue of origin. Below is a list of some broad categories of tumor as separated by tissue.
Carcinoma: tumors originating from epithelial cells, meaning cells that make up the thin protective barriers lining most organs, internal passageways/cavities and the skin. There are many more ways of further differentiating around specific epithelial tissues, some common largely agreed upon categories are squamous cell carcinomas referring to the top layer of the epidermis, basal cell carcinomas referring to the bottom layer of the epidermis, and adenocarcinomas referring to epithelial glands such as the endometrium or goblet cells. (1)
Melanoma: tumors of the cells that produce pigments in places such as the eyes and skin. And is usually developed due to sunlight exposure. Melanomas can be further classified by their specific origin. (2)
Leukemia: cancers of the bone marrow in which the bone marrow is producing too many improper blood cells. There are 4 main types of leukemia; these broad categories fit most leukemia cases within them. Firstly there are myelogenous and lymphoblastic leukemias (4). Myelogenous effects red blood cells platelets and a specific type of white blood cell that matures into a subcategory of phagocytes called myeloblasts. Lymphoblastic leukemias refers to leukemia to do with specifically lymphocytes (3), the T and B cells discussed in the immune system section. Both myelogenous and lymphoblastic leukemia can be acute or chronic, this simply refers to the concentration of the mutated cancerous cells within the blood, acute being more than 20% and chronic being less than. Acute obviously having more intense symptoms than chronic usually needing faster medical attention than chronic which can sometimes be monitored for an extended duration before clinical intervention is necessary (4).
Lymphoma: blood cancer originating in the lymphatic system. Separated largely into hodgkins and non-hodgkins lymphoma. Hodgkin’s lymphoma is diagnosed by the presence of Reed Sternberg cells, (Non-Hodgkin’s lymphoma is then by contrast the lack of Reed Sternberg cells) which are abnormally large cells sometimes with 2 nucleases. There are a variety of other subtypes of lymphomas. (5) (6)
Myeloma: cancer of various plasma cells within the bone marrow replicating too much and abnormally usually spilling out into the bloodstream. Often called multiple myeloma as most patients have multiple sites the plasma cells have spread to. (7)
Sarcoma: cancer of connective tissues within the body such as muscle, bones, tendons etc. Generally these are separated into bone sarcomas, and soft tissue sarcomas meaning muscle, fat, etc. (8)
Neuroendocrine tumors: a system of nerves and glands used to produce and release hormones. This system normally works in processes such as digestion. (9)
Germ cell tumors: cancers of the cells that produce sex cells, sperm and egg. (10)
Brain tumors: cancer developed in brain tissue. It is rare for brain cancers to spread outside of the brain and are thus usually a localised problem. There are over 120 different types of brain cancer and going into all of them will once again be left to medical textbooks. (11)
Cancers can also be classified by their difference to regular cells. By studying the cytology of cells it can give clues as to how certain cancers may develop or react. There are also grades for how different cells look compared to the normal cells, cells that look close to normal could be grade 1 while vastly different cells could be grade 4. (12)
Lastly tumor stage is decided by the TNM system the Tumor size and type, the lymph Nodes it is present in, and whether it has Metastasized and where. This system is flexible and broad, and the rating can be adjusted based upon the available treatments and types of tumor. Generally there are 4 stages, below is a brief guide that aims to give a broad understanding of how the stages could be considered. (13)
Stage 1: localised and small.
Stage 2: larger but still usually localised or being only present in local lymph nodes.
Stage 3: has grown into surrounding tissues and has spread to nearby lymph nodes.
Stage 4: the cancer has metastasized to different organs or distant parts of the body.
(14)
| 1. | Basal and Squamous Cell Carcinoma | Non-melanoma Skin Cancer | Cancer Council Australia | Cancer Council Australia. Cancer Council Australia. Published 2026. Accessed July 11, 2026. https://www.cancer.org.au/types-of-cancer/non-melanoma-skin-cancer |
| 2. | Mayo Clinic. Melanoma – Symptoms and Causes. Mayo Clinic. Published December 30, 2023. Accessed July 11, 2026. https://www.mayoclinic.org/diseases-conditions/melanoma/symptoms-causes/syc-20374884 |
| 3. | Martin L. AML vs. ALL: Differences in symptoms, diagnosis, and survival. www.medicalnewstoday.com. Published September 24, 2021. Accessed July 11, 2026. https://www.medicalnewstoday.com/articles/aml-vs-all#differences |
| 4. | Chennamadhavuni A, Lyengar V, Mukkamalla SKR, Shimanovsky A. Leukemia. PubMed. Published January 17, 2023. Accessed July 11, 2026. https://www.ncbi.nlm.nih.gov/books/NBK560490/ |
| 5. | Cleveland Clinic. Lymphoma. Cleveland Clinic. Published June 9, 2023. Accessed July 11, 2026. https://my.clevelandclinic.org/health/diseases/22225-lymphoma |
| 6. | Lymphoma | Cancer Council Australia | Cancer Council Australia. Cancer Council Australia. Published 2026. Accessed July 11, 2026. https://www.cancer.org.au/types-of-cancer/lymphoma |
| 7. | Myeloma | Cancer Council Australia. Cancer Council Australia. Published 2026. Accessed July 11, 2026. https://www.cancer.org.au/types-of-cancer/myeloma |
| 8. | Sarcoma. Hudson Institute of Medical Research. Published December 3, 2024. Accessed July 11, 2026. https://hudson.org.au/disease/cancer/sarcoma/ |
| 9. | Neuroendocrine Tumours | Cancer Council Australia | Cancer Council Australia. Cancer Council Australia. Published 2026. Accessed July 11, 2026. https://www.cancer.org.au/types-of-cancer/rare-cancers/neuroendocrine-tumours |
| 10. | Germ cell tumours. Cancer Australia. Published 2023. Accessed July 11, 2026. https://www.canceraustralia.gov.au/cancer-types/childrens-cancer/types-childrens-cancer/germ-cell-tumours |
| 11. | Brain Tumor Types. www.hopkinsmedicine.org. Accessed July 11, 2026. https://www.hopkinsmedicine.org/health/conditions-and-diseases/brain-tumor/brain-tumor-types |
| 12. | National Cancer Institute. Tumor Grade – NCI. www.cancer.gov. Published August 1, 2022. Accessed July 11, 2026. https://www.cancer.gov/about-cancer/diagnosis-staging/diagnosis/tumor-grade |
| 13. | Cleveland Clinic. Cancer Staging System: What Do Stages and Grades Mean? Cleveland Clinic. Published 2022. Accessed July 11, 2026. https://my.clevelandclinic.org/health/diagnostics/22607-cancer-stages-grades-system |
| 14. | Carbone A. Cancer Classification at the Crossroads. Cancers. 2020;12(4):980. doi:10.3390/cancers12040980 |