The TNM classification for cutaneous melanoma is a system used to determine the stage of melanoma by assessing the size and extent of the primary tumor, the involvement of lymph nodes, and the presence of distant metastasis. The calculator takes three key inputs: tumor classification, lymph node classification, and distant metastasis, each assigned specific categories or descriptions.

Inputs:
1. Tumor Classification: This is categorized from Tx to T4b, where Tx indicates the primary tumor cannot be assessed, T0 means no evidence of primary tumor, Tis is melanoma in situ, and ranges to T4b, which indicates a tumor > 4 mm in thickness with ulceration.
2. Lymph Node Classification: Options range from Nx, indicating regional lymph nodes cannot be assessed, to N3c, which involves criteria such as the number of tumor-involved nodes and the presence of metastases.
3. Distant Metastasis: Classified from M0, meaning no distant metastasis, to M1d, indicating distant metastasis to the central nervous system.

Computation:
The calculator evaluates the inputs based on predefined logic to determine the stage of melanoma:

- Stage 0 is identified if the tumor is in situ (Tis), there is no lymph node metastasis (N0), and no distant metastasis (M0).
- Stages IA to IIC are determined based on varying combinations of tumor size, ulceration, and the absence of nodal and distant metastasis.
- Stages IIIA to IIID involve the presence of lymph node metastasis with combinations of primary tumor characteristics, without distant metastasis.
- Stage IV is assigned if any level of tumor classification and lymph node involvement is coupled with the presence of distant metastasis.
- If the necessary inputs do not fit into the criteria for the specified stages, the result is "Stage cannot be fully assessed."

The TNM classification for cutaneous melanoma is a staging system developed by the American Joint Committee on Cancer (AJCC). It is designed for the stratification of patients with cutaneous melanoma based on the extent of the disease, providing a standardized language for communication among clinicians and aiding in the decision-making process for treatment.

The primary components of the TNM classification include three parameters: Tumor (T), Nodes (N), and Metastasis (M). Each parameter is further divided into subcategories.

The Tumor (T) category describes the primary tumor's thickness and ulceration status. It is divided into four stages (T1 to T4) based on the Breslow thickness, with T1 being less than 1.0 mm and T4 being more than 4.0 mm. The presence of ulceration also modifies the T category.

The Nodes (N) category describes whether the melanoma has spread to the regional lymph nodes. It is divided into three stages (N0 to N3) based on the number and location of lymph nodes involved, and whether there is in-transit, satellite, or microsatellite metastasis.

The Metastasis (M) category describes whether the melanoma has spread to distant sites. It is divided into two stages (M0 and M1), with M1 further subdivided based on the location of distant metastasis and the serum lactate dehydrogenase (LDH) level.

The combination of T, N, and M categories determines the overall stage of the disease, ranging from stage 0 (in situ melanoma) to stage IV (distant metastatic disease). This comprehensive staging system allows for a more precise prognosis and guides the selection of appropriate therapeutic strategies.