Diagnostic tests typically include complete blood tests, urinalysis, urine culture, X-rays of the abdomen and chest, and bladder imaging. The definitive diagnosis of bladder cancer will require a tissue biopsy and subsequent examination of the cells under the microscope.

The diagnosis of urachal cancer can be difficult and usually requires a multidisciplinary approach. A calcification in the midline can be detected in some patients in abdominal imaging studies. A cystoscopy is helpful in most cases. For diagnosis evaluation of a tissue biopsy is needed, which is usually obtained by transurethral resection (TURBT). Measurement of serum concentrations of CEA, CA19-9 and CA125 can be helpful in monitoring urachal cancer

Because most bladder cancers are invasive into the bladder wall, surgical removal is usually not possible. The majority of transitional cell carcinomas are treated with either traditional chemotherapy or nonsteroidal anti-inflammatory drugs.

As of 2010 there is insufficient evidence to determine if screening for bladder cancer in people without symptoms is effective or not.

In 2013 a preliminary, small study of 98 samples of urine, all from men—24 who had cancer, and 74 with bladder-related problems but no cancer yet used a gas chromatograph to successfully examine the vapor from heated urine samples to identify cancer.

Cystoscopy, a procedure in which a flexible tube bearing a camera and various instruments is introduced into the bladder through the urethra allows diagnosis and by biopsying suspicious lesions.

The gold standard for diagnosing bladder cancer is biopsy obtained during cystoscopy. Urine cytology can be obtained in voided urine or at the time of the cystoscopy ("bladder washing"). Cytology is not very sensitive (a negative result cannot reliably exclude bladder cancer). There are newer non-invasive urine bound markers available as aids in the diagnosis of bladder cancer, including human complement factor H-related protein, high-molecular-weight carcinoembryonic antigen, and nuclear matrix protein 22 (NMP22). NMP22 is also available as a prescription home test. Other non-invasive urine based tests include the CertNDx Bladder Cancer Assay, which combines FGFR3 mutation detection with protein and DNA methylation markers to detect cancers across stage and grade, UroVysion, and Cxbladder.

The diagnosis of bladder cancer can also be done with a Hexvix/Cysview guided fluorescence cystoscopy (blue light cystoscopy, Photodynamic diagnosis), as an adjunct to conventional white-light cystoscopy. This procedure improves the detection of bladder cancer and reduces the rate of early tumor recurrence, compared with white light cystoscopy alone. Cysview cystoscopy detects more cancer and reduces recurrence. Cysview is marketed in Europe under the brand name Hexvix

However, visual detection in any form listed above, is not sufficient for establishing pathological classification, cell type or the stage of the present tumor. A so-called cold cup biopsy during an ordinary cystoscopy (rigid or flexible) will not be sufficient for pathological staging either. Hence, a visual detection needs to be followed by transurethral surgery. The procedure is called transurethral resection of bladder tumor (TURBT). Further, bimanual examination should be carried out before and after the TURBT to assess whether there is a palpable mass or if the tumour is fixed ("tethered") to the pelvic wall. The pathological classification obtained by the TURBT-procedure, is of fundamental importance for making the appropriate choice of ensuing treatment and/or follow-up routines.

Urachal cancer usually is an adenocarcinoma (about 90%) mostly with mucinous/colloidal histology. The histology can be difficult to distinguish especially from colorectal cancer and primary adenocarcinoma of the urinary bladder. Immunohistochemistry in this situation is of little help with stains for betaCatenin and Cytokeratin 7 can be helpful. Other rare types include urothelial carcinoma, squamous cell carcinoma, neuroendocrine carcinoma and sarcoma.

Diagnostic systems in use are the Sheldon system based on proposals from Wheeler and Hill and Mostofi. Recent diagnostic classification schemes have been proposed by Herr et al and Gopalan et al. For non-adenocarcinoma urachal cancer a diagnostic classification scheme has been proposed by Paner et al.

In the United States screening is typically recommended between the age of 50 and 75 years. For those between 76 and 85 years of age the decision to screen should be individualized. A number of screening methods can be used including stool based tests every 3 years, sigmoidoscopy every 5 years and colonoscopy every 10 years. For those at high risk, screenings usually begin at around 40. It is unclear which of these two methods is better. Colonoscopy may find more cancers in the first part of the colon but is associated with greater cost and more complications. For people with average risk who have had a high-quality colonoscopy with normal results, the American Gastroenterological Association does not recommend any type of screening in the 10 years following the colonoscopy. For people over 75 or those with a life expectancy of less than 10 years, screening is not recommended. It takes about 10 years after screening for one out of a 1000 people to benefit.

In Canada, among those 50 to 75 at normal risk, fecal immunochemical testing or FOBT is recommended every two years or sigmoidoscopy every 10 years. Colonoscopy is less preferred.

Some countries have national colorectal screening programs which offer FOBT screening for all adults within a certain age group, typically starting between age 50 and 60. Examples of countries with organised screening include the United Kingdom, Australia and the Netherlands.

Aspirin and celecoxib appear to decrease the risk of colorectal cancer in those at high risk. Aspirin is recommended in those who are 50 to 60 years old, do not have an increased risk of bleeding, and are at risk for cardiovascular disease to prevent colorectal cancer. It is not recommended in those at average risk. There is tentative evidence for calcium supplementation, but it is not sufficient to make a recommendation. Vitamin D intake and blood levels are associated with a lower risk of colon cancer.

Diagnosis is established by transurethral biopsy. Types of urethral cancer include transitional cell carcinoma, squamous cell carcinoma, adenocarcinoma, and melanoma.

These aggressive tumors are generally diagnosed at advanced stages and survival is generally shorter. The prognosis of SRCC and its chemosensitivity with specific regimens are still controversial as SRCC is not specifically identified in most studies and its poor prognosis may be due to its more advanced stage. One study suggests that its dismal prognosis seems to be caused by its intrinsic tumor biology, suggesting an area for further research.

The criteria for diagnosing BACs have changed since 1999. Under the new definition, BAC is defined as a tumor that grows in a lepidic (that is, a scaly covering) fashion along pre-existing airway structures, without detectable invasion or destruction of the underlying tissue, blood vessels, or lymphatics. Because invasion must be ruled out, BAC can be diagnosed only after complete sectioning and examination of the entire tumor, not using biopsy or cytology samples. BAC is considered a pre-invasive malignant lesion that, after further mutation and progression, eventually generates an invasive adenocarcinoma. Therefore, it is considered a form of carcinoma "in situ" (CIS).

Large-cell carcinoma (LCC), like small-cell carcinoma (SCC) is very rare and only accounts for about 5% of all cervical cancers. Early-stage LCC are extremely aggressive and difficult to diagnose due to the sub-mucosal location of the tumor and intact overlying mucosa. As with SCC, in LCC early cases are asymptomatic. Later stages present with irregular bleeding, vaginal spotting, discharge, and pelvic pain. The basis for treatment of LCC tumors is derived from therapy used for SCC; when diagnosed, multimodal therapy should be considered just as with SCC.

People with Barrett's esophagus (a change in the cells lining the lower esophagus) are at much higher risk, and may receive regular endoscopic screening for the early signs of cancer. Because the benefit of screening for adenocarcinoma in people without symptoms is unclear, it is not recommended in the United States. Some areas of the world with high rates of squamous-carcinoma have screening programs.

Primary signet-ring cell carcinoma of the urinary bladder is extremely rare and patient survival is very poor and occurs mainly in men ages 38 to 83. However, one such patient treated with a radical cystectomy followed by combined S-1 and Cisplatin adjuvant chemotherapy did demonstrate promising long-term survival of 90 months.

HGPIN is diagnosed from tissue by a pathologist, which may come from:

- a needle biopsy taken via the rectum and,

- surgical removal of prostate tissue:

- transurethral resection of the prostate - removal of extra prostate tissue to improve urination (a treatment for benign prostatic hyperplasia),

- radical prostatectomy - complete removal of prostate and seminal vesicles (a treatment for prostate cancer).

Blood tests for prostate specific antigen (PSA), digital rectal examination, ultrasound scanning of the prostate via the rectum, fine needle aspiration or medical imaging studies (such as magnetic resonance imaging) are "not" useful for diagnosing HGPIN.

This disease is often discovered during surgery for other conditions, e.g., hernia repair, following which an experienced pathologist can confirm the diagnosis. Advanced stages may present as tumors palpable on the abdomen or distention of the belly ("jelly belly" is sometimes used as a slang term for the condition). Due to the rarity of this disease, it is important to obtain an accurate diagnosis so that appropriate treatment may be obtained from a surgical oncologist who specializes in appendix cancer. Diagnostic tests may include CT scans, examination of tissue samples obtained through laparoscopy, and the evaluation of tumor markers. In most cases a colonoscopy is unsuitable as a diagnostic tool because in most cases appendix cancer invades the abdominal cavity but not the colon (however, spread inside the colon is occasionally reported). PET scans may be used to evaluate high-grade mucinous adenocarcinoma, but this test is not reliable for detecting low-grade tumors because those do not take up the dye which shows up on scans. New MRI procedures are being developed for disease monitoring, but standard MRIs are not typically used as a diagnostic tool. Diagnosis is confirmed through pathology.

Prognosis is highly variable and dependent upon a multitude of factors. Reoccurrence does occur. Treatment is determined on a case-by-case basis.

Several tests are used to diagnose vaginal cancer, including:

- Physical exam and history

- Pelvic exam

- Pap smear

- Biopsy

- Colposcopy

Recommendations for women with vaginal cancer is not to have routine surveillance imaging to monitor the cancer unless they have new symptoms or rising tumor markers. Imaging without these indications is discouraged because it is unlikely to detect a recurrence or improve survival, and because it has its own costs and side effects. MRI provides visualization of the extent of vaginal cancer.

Prevention

HGPIN in isolation does not require treatment. In prostate biopsies it is not predictive of prostate cancer in one year if the prostate was well-sampled, i.e. if there were 8 or more cores.

The exact timing of repeat biopsies remains an area of controversy, as the time required for, and probability of HGPIN transformations to prostate cancer are not well understood.

LCIS (lobular neoplasia is considered pre-cancerous) is an indicator (marker) identifying women with an increased risk of developing invasive breast cancer. This risk extends more than 20 years. Most of the risk relates to subsequent invasive ductal carcinoma rather than to invasive lobular carcinoma.

While older studies have shown that the increased risk is equal for both breasts, a more recent study suggests that the ipsilateral (same side) breast may be at greater risk.

Staging is based on the TNM staging system, which classifies the amount of tumor invasion (T), involvement of lymph nodes (N), and distant metastasis (M). The currently preferred classification is the 2010 AJCC staging system for cancer of the esophagus and the esophagogastric junction. To help guide clinical decision making, this system also incorporates information on cell type (ESCC, EAC, etc.), grade (degree of differentiation – an indication of the biological aggressiveness of the cancer cells), and tumor location (upper, middle, lower, or junctional).

A multi-step carcinogenesis hypothesis suggests a progression from pulmonary atypical adenomatous hyperplasia (AAH) through bronchioalveolar carcinoma (BAC) to invasive adenocarcinoma (AC), but to date this has not been formally demonstrated.

It has been observed that HPV18 is the most prevalent type in Small cell cervical cancer.

Like other types of cervical cancer it seems to be associated with high-risk (e.g. 16, 18, 31) HPV Infection.

For surface epithelial-stromal tumors, the most common sites of metastasis are the pleural cavity (33%), the liver (26%), and the lungs (3%).

LCIS may be treated with close clinical follow-up and mammographic screening, tamoxifen or related hormone controlling drugs to reduce the risk of developing cancer, or bilateral prophylactic mastectomy. Some surgeons consider bilateral prophylactic mastectomy to be overly aggressive treatment except for certain high-risk cases.