Diagnosis of adenocarcinoma usually requires examination of the tissues under the microscope. Since adenocarcinoma occurs from the epithelial tissues, they can affect a wide range of organs.

After taking a biopsy or sample of the cancer tissue, it is sliced into microscopically thin slices or wafers. These are then fixed onto a glass slide and stained using special dyes. The dye usually stains pink and blue. Under the microscope glandular tissues are seen.

Diagnostic challenge

When the adenocarcinoma clearly reveals cancerous abnormal growth of glands it can be easily identified. However, if the formations of the glands are not very clearly demarcated, it is known as adenocarcinoma not otherwise specified or adenocarcinoma NOS. This indicates that there is an underlying cancerous process in progress.

Adenocarcinoma not otherwise specified is often a preliminary diagnosis and can frequently be clarified by a pathologist with the use of immunohistochemistry. However, such a state is not very useful for treatment decisions and prognosis, as these are determined by the tissue from which the tumour cells arose, i.e. the tissue of origin. Cancer for which a primary site cannot be found is called cancer of unknown primary.

Diagnostic significance

Diagnosis and identification of the adenocarcinoma is important for staging of the cancer that finally helps in determining the treatment plan and possible outcome of the cancer.

Both treatment and prognosis or outcome of the cancer is dependent on the target organ or the organ in which the cancer has originated. For example, an adenocarcinoma of the colon has a different prognosis and treatment than an adenocarcinoma of the ovary.

Staging adenocarcinoma

Since primary treatment involves a surgical resection of the cancer, the initial step is to determine if the cancer is surgically resectable or removable or not.

Another initial determinant is if the cancer has spread to other organs. In patients with a locally advanced cancer the cancer has grown out of the primary organ (e.g. pancreas) to involve surrounding structures particularly blood vessels that are closely associated with the organ. Invasion of the cancer into these blood vessels means removal of the cancer by surgery is not possible. Some patients with locally advanced tumor may respond to chemotherapy and/or radiation therapy and shrinkage of the tumor may allow the surgeon to remove the cancer.

The staging system commonly used especially for colon or intestinal cancer is that of the American Joint Committee on Cancer (AJCC). It is also called the TNM system. Stages are described using Roman numerals I through IV. This staging system describes the spread of the cancer in relation to the layers of the wall of the intestine.

The AJCC/TNM System describes the extent of the primary Tumor (T), the absence or presence of metastasis to nearby lymph Nodes (N), and the absence or presence of distant Metastasis (M).