Diagnosis is confirmed via biopsy of the tissue(s) suspected to be affected by SCC. For the skin, look under skin biopsy.

The pathological appearance of a squamous cell cancer varies with the depth of the biopsy. For that reason, a biopsy including the subcutaneous tissue and basalar epithelium, to the surface is necessary for correct diagnosis. The performance of a shave biopsy (see skin biopsy) might not acquire enough information for a diagnosis. An inadequate biopsy might be read as actinic keratosis with follicular involvement. A deeper biopsy down to the dermis or subcutaneous tissue might reveal the true cancer. An excision biopsy is ideal, but not practical in most cases. An incisional or punch biopsy is preferred. A shave biopsy is least ideal, especially if only the superficial portion is acquired.

Sunscreen is effective and thus recommended to prevent melanoma and squamous-cell carcinoma. There is little evidence that it is effective in preventing basal-cell carcinoma. Other advice to reduce rates of skin cancer includes avoiding sunburning, wearing protective clothing, sunglasses and hats, and attempting to avoid sun exposure or periods of peak exposure. The U.S. Preventive Services Task Force recommends that people between 9 and 25 years of age be advised to avoid ultraviolet light.

The risk of developing skin cancer can be reduced through a number of measures including decreasing indoor tanning and mid day sun exposure, increasing the use of sunscreen, and avoiding the use of tobacco products.

There is insufficient evidence either for or against screening for skin cancers. Vitamin supplements and antioxidant supplements have not been found to have an effect in prevention. Evidence for a benefit from dietary measures is tentative.

Zinc oxide and titanium oxide are often used in sun screen to provide broad protection from UVA and UVB ranges.

Eating certain foods may decrease the risk of sunburns but this is much less than the protection provided by sunscreen.

The mortality rate of basal-cell and squamous-cell carcinoma are around 0.3%, causing 2000 deaths per year in the US. In comparison, the mortality rate of melanoma is 15–20% and it causes 6500 deaths per year. Even though it is much less common, malignant melanoma is responsible for 75% of all skin cancer-related deaths.

The survival rate for people with melanoma depends upon when they start treatment. The cure rate is very high when melanoma is detected in early stages, when it can easily be removed surgically. The prognosis is less favorable if the melanoma has spread to other parts of the body. As of 2003 the overall five year cure rate with Mohs' micrographic surgery was around 95 percent for recurrent basal cell carcinoma.

Australia and New Zealand exhibit one of the highest rates of skin cancer incidence in the world, almost four times the rates registered in the United States, the UK and Canada. Around 434,000 people receive treatment for non-melanoma skin cancers and 10,300 are treated for melanoma. Melanoma is the most common type of cancer in people between 15–44 years in both countries. The incidence of skin cancer has been increasing. The incidence of melanoma among Auckland residents of European descent in 1995 was 77.7 cases per 100,000 people per year, and was predicted to increase in the 21st century because of "the effect of local stratospheric ozone depletion and the time lag from sun exposure to melanoma development."

Following a visual examination and a dermatoscopic exam, or "in vivo" diagnostic tools such as a confocal microscope, the doctor may biopsy the suspicious mole. A skin biopsy performed under local anesthesia is often required to assist in making or confirming the diagnosis and in defining severity. Elliptical excisional biopsies may remove the tumor, followed by histological analysis and Breslow scoring. Incisional biopsies such as punch biopsies are usually contraindicated in suspected melanomas, because of the possibility of sampling error or local implantation causing misestimation of tumour thickness. However, fears that such biopsies may increase the risk of metastatic disease seem unfounded.

Total body photography, which involves photographic documentation of as much body surface as possible, is often used during follow-up for high-risk patients. The technique has been reported to enable early detection and provides a cost-effective approach (with any digital camera), but its efficacy has been questioned due to its inability to detect macroscopic changes. The diagnosis method should be used in conjunction with (and not as a replacement for) dermoscopic imaging, with a combination of both methods appearing to give extremely high rates of detection.

Lactate dehydrogenase (LDH) tests are often used to screen for metastases, although many patients with metastases (even end-stage) have a normal LDH; extraordinarily high LDH often indicates metastatic spread of the disease to the liver.

It is common for patients diagnosed with melanoma to have chest X-rays and an LDH test, and in some cases CT, MRI, PET and/or PET/CT scans. Although controversial, sentinel lymph node biopsies and examination of the lymph nodes are also performed in patients to assess spread to the lymph nodes. A diagnosis of melanoma is supported by the presence of the S-100 protein marker.

HMB-45 is a monoclonal antibody that reacts against an antigen present in melanocytic tumors such as melanomas. It is used in anatomic pathology as a marker for such tumors. The antibody was generated to an extract of melanoma. It reacts positively against melanocytic tumors but not other tumors, thus demonstrating specificity and sensitivity. The antibody also reacts positively against junctional nevus cells but not intradermal nevi, and against fetal melanocytes but not normal adult melanocytes.

HMB-45 is nonreactive with almost all non-melanoma human malignancies, with the exception of rare tumors showing evidence of melanogenesis (e.g., pigmented schwannoma, clear cell sarcoma) or tumors associated with tuberous sclerosis complex (angiomyolipoma and lymphangiomyoma).

Appropriate sun-protective clothing, use of broad-spectrum (UVA/UVB) sunscreen with at least SPF 50, and avoidance of intense sun exposure may prevent skin cancer.

Definitive diagnosis of Merkel cell carcinoma (MCC) requires examination of biopsy tissue. An ideal biopsy specimen is either a punch biopsy or a full-thickness incisional biopsy of the skin including full-thickness dermis and subcutaneous fat. In addition to standard examination under light microscopy, immunohistochemistry (IHC) is also generally required to differentiate MCC from other morphologically similar tumors such as small cell lung cancer, the small cell variant of melanoma, various cutaneous leukemic/lymphoid neoplasms, and Ewing's sarcoma. Similarly, most experts recommend longitudinal imaging of the chest, typically a CT scan, to rule out that the possibility that the skin lesion is a cutaneous metastasis of an underlying small cell carcinoma of the lung.

The U.S. Preventive Services Task Force (USPSTF) issues recommendations for various cancers:

- Strongly recommends cervical cancer screening in women who are sexually active and have a cervix at least until the age of 65.

- Recommend that Americans be screened for colorectal cancer via fecal occult blood testing, sigmoidoscopy, or colonoscopy starting at age 50 until age 75.

- Evidence is insufficient to recommend for or against screening for skin cancer, oral cancer, lung cancer, or prostate cancer in men under 75.

- Routine screening is not recommended for bladder cancer, testicular cancer, ovarian cancer, pancreatic cancer, or prostate cancer.

- Recommends mammography for breast cancer screening every two years from ages 50–74, but does not recommend either breast self-examination or clinical breast examination. A 2013 Cochrane review concluded that breast cancer screening by mammography had no effect in reducing mortality because of overdiagnosis and overtreatment.

Screens for gastric cancer using photofluorography due to the high incidence there.

Prognosis is excellent if the appropriate method of treatment is used in early primary basal-cell cancers. Recurrent cancers are much harder to cure, with a higher recurrent rate with any methods of treatment. Although basal-cell carcinoma rarely metastasizes, it grows locally with invasion and destruction of local tissues. The cancer can impinge on vital structures like nerves and result in loss of sensation or loss of function or rarely death. The vast majority of cases can be successfully treated before serious complications occur. The recurrence rate for the above treatment options ranges from 50 percent to 1 percent or less.

Lymphoma is the most common type of blood-related cancer in horses and while it can affect horses of all ages, it typically occurs in horses aged 4–11 years.

Basal-cell carcinoma is a common skin cancer and occurs mainly in fair-skinned patients with a family history of this cancer. Sunlight is a factor in about two-thirds of these cancers; therefore, doctors recommend sunscreens with at least SPF 30. One-third occur in non-sun-exposed areas; thus, the pathogenesis is more complex than UV exposure as "the" cause.

The use of a chemotherapeutic agent such as 5-Fluorouracil or imiquimod, can prevent development of skin cancer. It is usually recommended to individuals with extensive sun damage, history of multiple skin cancers, or rudimentary forms of cancer (i.e., solar keratosis). It is often repeated every 2 to 3 years to further decrease the risk of skin cancer.

Breast cancer screening refers to testing otherwise-healthy women for breast cancer in an attempt to achieve an earlier diagnosis under the assumption that early detection will improve outcomes. A number of screening tests have been employed including clinical and self breast exams, mammography, genetic screening, ultrasound, and magnetic resonance imaging.

A clinical or self breast exam involves feeling the breast for lumps or other abnormalities. Clinical breast exams are performed by health care providers, while self-breast exams are performed by the person themselves. Evidence does not support the effectiveness of either type of breast exam, as by the time a lump is large enough to be found it is likely to have been growing for several years and thus soon be large enough to be found without an exam. Mammographic screening for breast cancer uses X-rays to examine the breast for any uncharacteristic masses or lumps. During a screening, the breast is compressed and a technician takes photos from multiple angles. A general mammogram takes photos of the entire breast, while a diagnostic mammogram focuses on a specific lump or area of concern.

A number of national bodies recommend breast cancer screening. For the average woman, the U.S. Preventive Services Task Force recommends mammography every two years in women between the ages of 50 and 74, the Council of Europe recommends mammography between 50 and 69 with most programs using a 2-year frequency, and in Canada screening is recommended between the ages of 50 and 74 at a frequency of 2 to 3 years. These task force reports point out that in addition to unnecessary surgery and anxiety, the risks of more frequent mammograms include a small but significant increase in breast cancer induced by radiation.

The Cochrane collaboration (2013) states that the best quality evidence neither demonstrates a reduction in cancer specific, nor a reduction in all cause mortality from screening mammography. When less rigorous trials are added to the analysis there is a reduction in mortality due to breast cancer of 0.05% (a decrease of 1 in 2000 deaths from breast cancer over 10 years or a relative decrease of 15% from breast cancer). Screening over 10 years results in a 30% increase in rates of over-diagnosis and over-treatment (3 to 14 per 1000) and more than half will have at least one falsely positive test. This has resulted in the view that it is not clear whether mammography screening does more good or harm. Cochrane states that, due to recent improvements in breast cancer treatment, and the risks of false positives from breast cancer screening leading to unnecessary treatment, "it therefore no longer seems beneficial to attend for breast cancer screening" at any age. Whether MRI as a screening method has greater harms or benefits when compared to standard mammography is not known.

Treatment of small melanomas is often not necessary, but large tumors can cause discomfort and are usually surgically removed. Cisplatin and cryotherapy can be used to treat small tumors less than 3 centimeters, but tumors may reoccur. Cimetidine, a histamine stimulator, can cause tumors to regress in some horses, but may take up to 3 months to produce results and multiple treatments may be needed throughout the horse's life. There are few viable treatment options for horses with metastatic melanoma. However, gene therapy injections utilizing interleukin-12 and 18-encoding DNA plasmids have shown promise in slowing the progression of tumors in patients with metastatic melanoma.

A research article from 1923 notes that the “average duration of life” in those with Kangri cancer is about fifteen months, though there have been records of people dying within one year and living for more than twenty years with Kangri cancer. Updated life expectancy is not found in more recent scientific publications.

However, in 2013, it was noted that the progression from erythema ab igne to squamous cell carcinoma, manifesting as Kangri cancer, was between one to two decades.

It has been reported that about one-third to one-half of patients with Kangri cancer show metastasis to local lymph nodes.

In the treatment of Kangri cancer, surgery is, most often, the first-line course of action to remove the primary tumor.

As soon as a tumor is detected, diagnosing the type of cancer remains a primary objective, as it helps determine the best possible treatment by the analysis of the structure of the tumor and cancer cells.

Anatomical staging supplemented preclinical staging starting in 1988. FIGO’s revised TNM classification system uses tumor size (T), lymph node involvement (N) and presence or absence of metastasis (M) as criteria for staging. Stages I and II describe the early stages of vulvar cancer that still appear to be confined to the site of origin. Stage III cancers include greater disease extension to neighboring tissues and inguinal lymph nodes on one side. Stage IV indicates metastatic disease to inguinal nodes on both sides or distant metastases.

Overall, five-year survival rates for vulvar cancer are around 78% but may be affected by individual factors including cancer stage, cancer type, patient age and general medical health. Five-year survival is greater than 90% for patients with stage I lesions but decreases to 20% when pelvic lymph nodes are involved. Lymph node involvement is the most important predictor of prognosis. Thus, early diagnosis is important.

Since Merkel-cell cancer is uncommon and difficult to diagnose, patients may want a second opinion about the diagnosis and treatment plan before starting treatment. However, early diagnosis and treatment of Merkel-cell cancers are important factors in decreasing the chance of metastasis, after which it is exceptionally difficult to cure.

The number of studies focusing on the development of new targeted anticancer therapy is steadily rising, and thus there is hope that new drug regimes for patients with distant and systemic Merkel-cell carcinoma disease will be available in the near future. In particular, many study groups are looking for new strategies to target the MCV either to prevent infection or to inhibit viral-induced carcinogenesis.

Even highly advanced metastatic Merkel cell carcinoma can be responsive to PD-1 inhibitor treatment, providing promise for new chemotherapeutic and immunotherapeutic options.

The selective estrogen receptor modulators (such as tamoxifen) reduce the risk of breast cancer but increase the risk of thromboembolism and endometrial cancer. There is no overall change in the risk of death. They are thus not recommended for the prevention of breast cancer in women at average risk but may be offered for those at high risk. The benefit of breast cancer reduction continues for at least five years after stopping a course of treatment with these medications.

80% of cases in the United States are diagnosed by mammography screening.

Treatments of cancer in cats usually consists of diagnosis and observation of the tumor to determine its type and size, the development of a treatment plan, the associated goals on the part of the treatment methods, and the regular evaluation of the overall health of the pet.

Treatment options vary and depend on the type and stage of cancer. Common treatments include surgery, chemotherapy, radiation therapy, amputation, and immunotherapy. A combination of therapies may be used. Knowledge and treatment of cancer have increased significantly in the past three decades. Survival rates have also increased due to the increase prevalence of canine cancer treatment centers and breakthroughs in targeted drug development. Canine cancer treatment has become an accepted clinical practice and access to treatment for owners has widely expanded recently. Cancer-targeting drugs most commonly function to inhibit excessive cell proliferation by attacking the replicating cells. However, there is still a prevalent pharmacy gap in veterinary oncology.

There is one canine tumor vaccine approved by the USDA, for preventing canine melanoma. The Oncept vaccine activates T-cell responses and antibodies against tumor-specific tyrosinase proteins. There is limited information about canine tumor antigens, which is the reason for the lack of tumor-specific vaccines and immunotherapy treatment plans for dogs.

Success of treatment depends on the form and extent of the cancer and the aggressiveness of the therapy. Early detection offers the best chance for successful treatment. The heterogeneity of tumors makes drug development increasingly complex, especially as new causes are discovered. No cure for cancer in canines exist.

Some dog owners opt for no treatment of the cancer at all, in which case palliative care, including pain relief, may be offered. Regardless of how treatment proceeds following a diagnosis, the quality of life of the pet is an important consideration. In cases where the cancer is not curable, there are still many things which can be done to alleviate the dog's pain. Good nutrition and care from the dog's owner can greatly enhance quality of life.

Typically, either cytologic or histopathologic analysis of the suspected mass is done prior to initiating treatment. The commonly used diagnostic procedures for skin tumors are fine-needle aspiration cytology and tissue biopsy.

Cytology is an important tool that can help the veterinarian distinguish a tumor from inflammatory lesions. The biopsy technique used will largely depend on the tumor's size and location. Small masses are usually completely excised and sent to the pathology lab to confirm that the surrounding healthy tissues that were excised along with the tumor do not contain any cancer cells. If the tumor is larger, a small sample is removed for analysis and depending on the results, appropriate treatment is chosen. Depending on the tumor type and its level of aggressiveness, additional diagnostic tests can include blood tests to assess the pet’s overall health, chest X-rays to check for lung metastasis, and abdominal ultrasound to check for metastasis to other internal organs.