Secondary and unspecified malignant neoplasm of lymph nodes, site unspecified

This code signifies the presence of metastatic cancer within lymph nodes when the primary tumor site is unknown or not specified in the medical record. It indicates that the lymph nodes are involved with a secondary malignancy, rather than being the origin of the cancer.

Apply this code when documentation confirms metastatic lymph node involvement but the primary malignant neoplasm's location is either undetermined after investigation or not documented. This is often used in cases of carcinoma of unknown primary (CUP) where only lymph node metastases are identified.

• Always attempt to identify the primary site of malignancy before using this code.
• Do not use if the primary site is known, even if the lymph node involvement is secondary; instead, code the primary malignancy and the specific secondary site.
• This code should be sequenced after the primary malignancy if known, or as the principal diagnosis if the primary is truly unknown and only the lymph node metastasis is being treated/investigated.