cancer staging

Diagnostic evaluation of malignancy includes determination of the cancer's pathology (tissue type, organ of origin) in addition to staging of the cancer to determine degree of local, regional, and distant spread. Clinical and pathological staging is important to decisions concerning therapy, and to estimating prognosis (a statistical measure).

The stage of a cancer is influenced by:
¤ the carcinoma's biological aggressiveness
¤ time elapsed before clinical/pathologic diagnosis – c, cs = clinical; p, ps = pathological
¤ time elapsed before/since institution of anti-cancer treatment
¤ the tumor's sensitivity to cytotoxic therapies

Cancers commence as in situ colonies of cells that have escaped normal cellular controls. Local overgrowth of the primary tumor (localized) is followed by local tissue infiltration, and ultimately by malignant penetration of adjacent tissues (regional), blood vessels or lymphatics, with shedding and transport of malignant cells and ultimate colonization of distant organs (distant, secondary tumors, metastases).

Staging systems reflect this biological progression and the tissue type. The system of staging employed will depend, to some extent, upon the specific form of cancer involved – whether it is a solid tumor or hematologic, whether it belongs to a group staged by a specific system, such as the Ann Arbor staging classification that is commonly employed to stage lymphomas.

Cell type and grade is used to stage carcinomas of the brain and spinal cord.

TNM system – Tumor, Node, Metastasis
T refers to the primary (solid) tumor – X (cannot be evaluated), 'is' (in situ), 0 - 4 (size/extent)
N refers to regional lymph node involvement – X, 0-4 (extent)
M refers to metastasis – X, 0 = no metastasis, 1 = metastasis

Ann Arbor System (lymphomas)
Stage I – single region, typically a single lymph node and the surrounding area
Stage II – two regions on same side of diaphragm, an affected lymph node or organ within the lymphatic system and a second affected area
Stage III – both sides of diaphragm, including organ or area adjacent to lymph nodes or spleen
Stage IV – diffuse or disseminated involvement of one or more extralymphatic organs, including any involvement of the liver, bone marrow, or nodular involvement of the lungs.

Modifications to Ann Arbor
A = absence of constitutional symptoms
B = presence of constitutional symptoms (night sweats, fevers, unexplained weight loss of >10%)
E = "extranodal" (not in the lymph nodes) or spread from lymph nodes to adjacent tissue
X = largest deposit if >10 cm large ("bulky disease"), or mediastinum is wider than 1/3 of the chest on a chest X-ray

"Staging: Questions and Answers" at the National Cancer Institute
International Union Against Cancer, TNM