Metastatic (Secondary) Cancer ICD-10-CM codes

Secondary (metastatic) neoplasms are coded by the site of the metastasis: C77 for lymph nodes by region, C78 for respiratory and digestive organs (C78.0- lung, C78.2 pleura, C78.7 liver, C78.6 peritoneum), and C79 for all other sites (C79.31 brain, C79.51 bone, C79.52 bone marrow, C79.2 skin, C79.6- ovary, C79.7- adrenal). Sites with laterality carry it in the fifth character. Always code the primary site as well, and code each metastatic site separately.

Sequencing depends on the focus of the encounter. When treatment is directed at the primary, the primary is sequenced first and the secondary sites follow. When treatment is directed only at a metastatic site, for example radiation to bone metastases, the C79.51 code is principal and the primary is an additional code. If the primary has been previously excised and there is no evidence of it, use the Z85 history code for the primary together with the C77 to C79 code for the current metastasis.

Documentation language matters. Metastatic carcinoma of the lung means a secondary tumor in the lung (C78.0-); carcinoma metastatic from the lung means the lung is the primary (C34.-). When the primary cannot be determined, assign C80.1 (malignant neoplasm, primary site unspecified) with the secondary site codes. C80.0 (disseminated malignant neoplasm) is for widespread carcinomatosis where neither the primary nor specific secondary sites are documented, and C79.9 is a secondary neoplasm of unspecified site. These unspecified codes should be replaced as soon as the record identifies the sites.

Complications of metastatic disease are coded in addition: malignant pleural effusion J91.0, pathological fracture in neoplastic disease M84.5-, hypercalcemia E83.52, and anemia in neoplastic disease D63.0. Neoplasm-related pain is G89.3 and is sequenced first when the encounter is for pain control rather than treatment of the tumor.