Collaborative Stage

Note 1: Record the status of isolated tumor cells as recorded by the pathologist. For Merkel cell carcinoma, the presence of isolated tumor cells in regional lymph node(s) is considered as positive nodal involvement.
Note 2: Isolated tumor cells (ITCs) are defined as single tumor cells or small clusters not greater than 0.2 mm, usually detected by immunohistochemical (IHC) methods such as Cytokeratin 20 (CK20) or CAM 5.2 or pancytokeratins.
Note 3: If regional lymph nodes were removed and were pathologically negative with no mention of ITC status, assume there are no ITC's and assign code 000.

Code	Description
000	Regional lymph nodes negative on routine H and E, no IHC studies for ITCs done (CK20, CAM5.2, pancytokeratins) or unknown if IHC studies done Nodes clinically negative, not examined pathologically
010	Regional lymph nodes negative on routine H and E, IHC studies done (CK20, CAM5.2, pancytokeratins) and ITCs NOT PRESENT
020	Regional lymph nodes negative on routine H and E, IHC studies done (CK20, CAM5.2, pancytokeratins) and ITCs (tumor cell clusters not greater than 0.2mm) PRESENT
090	Regional lymph nodes negative on routine H and E, positive for tumor detected by IHC, size of tumor cell clusters or metastases not stated
100	Regional lymph nodes positive with ITCs on routine H and E
200	Regional lymph nodes positive with ITCs, NOS, method of detection not stated
300	Regional lymph nodes positive other than ITCs (tumor cells greater than 0.2 mm)
988	Not applicable: Information not collected for this case
999	Unknown or no information Not documented in pathology report or patient record

CS Site-Specific Factor 18
Isolated Tumor Cells (ITCs) in Regional Lymph Node(s)