The Modified Ann Arbor classification for non-Hodgkin's lymphoma is a tool to determine the stage of lymphoma by analyzing three critical aspects of the patient's condition:

- Lymph Node Involvement
- Extralymphatic Organ/Site Involvement
- Spleen Involvement

Each aspect offers a range of conditions:

1. Lymph Node Involvement can range from no involvement to distant (nonregional) nodes.
2. Extralymphatic Organ/Site Involvement can vary from none to multifocal involvement of one or more organs/sites.
3. Spleen Involvement is identified simply as either present (Yes) or absent (No).

Based on these inputs, the classification process identifies the stage of the lymphoma through specific combinations:

- Stage I is assigned when a single lymph node region is involved, without any extralymphatic organ involvement or spleen involvement.
- Stage IE occurs with no lymph node involvement but a single organ/site is affected, and the spleen is not involved.
- Stage II indicates involvement of multiple lymph node regions on the same side of the diaphragm, without extralymphatic organ or spleen involvement.
- Stage IIE results from regional lymph nodes of a single extralymphatic organ or site (potentially combined with other lymph nodes on the same diaphragm side), provided the spleen is not involved.
- Stage III classification is for lymph node regions on both sides of the diaphragm with neither extralymphatic nor spleen involvement.
- Stage IIIE is determined when both sides of the diaphragm have lymph node involvement along with a single organ/site, but without spleen involvement.
- Stage IIIS emerges when both diaphragm sides have lymph node involvement with spleen involvement, but no extralymphatic organ involvement.
- Stage IIIE+S results from the same conditions as IIIS, but with the addition of a single organ/site being involved.
- Stage IV can be determined when there is any lymph node involvement (even single or multiple on the same diaphragm side) alongside multifocal organ involvement, regardless of spleen status.
- Stage IVE occurs when distant (nonregional) lymph nodes are involved along with a single organ, and spleen involvement is inconsequential to this determination.

This meticulous classification framework ensures precise categorization of lymphomas based on the combination and extent of lymph node and organ involvement, supplemented by spleen status, enabling tailored treatment and management approaches.

The Modified Ann Arbor Classification is a staging system specifically used for non-Hodgkin's lymphoma (NHL). This classification system is used to determine the extent of the disease and to guide treatment decisions. It is based on the number of lymph node regions involved, the presence of extranodal disease, and whether the disease is localized or disseminated. 

The patient population for this calculator includes individuals diagnosed with non-Hodgkin's lymphoma. The clinical utility of the Modified Ann Arbor Classification is to provide a standardized method for staging NHL, which is crucial for prognosis and treatment planning. 

There are no specific exclusion criteria for its use, but it is less applicable to patients with certain types of lymphoma that do not typically present with nodal disease, such as primary cutaneous lymphomas. It is also less useful in the pediatric population, where lymphomas often have different characteristics and behavior compared to adults.