Ann Arbor staging of lymphoma

What it is

Ann Arbor staging is the staging used for lymphoma, and it is built around the diaphragm. Once the lymphoma has been diagnosed by excisional biopsy, staging is the next step in management.

How it is diagnosed

The four stages:

Stage I: localized disease, a single lymph node region or a single organ, that is one node group
Stage II: two or more lymph node regions on the same side of the diaphragm
Stage III: two or more lymph node regions above and below the diaphragm
Stage IV: widespread disease, multiple organs, with or without lymph node involvement

The two accounts of the higher stages do not agree in full. Stage III is given as nodes on both sides of the diaphragm alone in one, and with extension into an organ added to it in another; stage IV is given as multiple organs in one and as bone marrow or liver in the other.

Staging itself runs in order:

CXR
CT of the abdomen, pelvis and chest, or a PET scan; MRI is named alongside CT
Bone marrow biopsy, to rule out bone marrow involvement, and only if the first two are negative

Bone marrow biopsy matters especially for non-Hodgkin lymphoma. If still unsure after the CT or MRI, staging laparotomy is done.