C79.51

Billable

Secondary malignant neoplasm of bone

HCC Category Mapping

V28HCC 18 — Metastatic Cancer to Peritoneum and Other Specified Sites

0.368

V24HCC 8 — Metastatic Cancer and Acute Leukemia

2.484

ESRDHCC 8 — Metastatic Cancer and Acute Leukemia

0.000

RxHCCHCC 17 — Metastatic Cancer to Kidney, Bone, and Other Sites

0.000

What This Code Means

Cancer that has spread to the bone from a primary cancer located elsewhere in the body.

Coding Tips

•Bone metastases are common in many cancers; document the specific bone site affected if possible for treatment planning purposes
•Distinguish from primary bone cancers (C40.x-C41.x codes); secondary bone malignancies require coding of the primary site separately

Clinical Significance

Secondary malignant neoplasm of bone is one of the most common sites of distant metastasis, frequently seen with breast, prostate, lung, kidney, and thyroid cancers. Bone metastases cause significant morbidity including pathological fractures, hypercalcemia, spinal cord compression, and severe pain. They are a major driver of cancer-related healthcare utilization and substantially affect quality of life.

Documentation Requirements

✓Primary cancer site documented and coded separately
✓Specific bones affected — spine, pelvis, femur, ribs, skull, etc.
✓Imaging confirmation — bone scan, PET scan, CT, MRI, or X-ray
✓Whether lesions are osteolytic, osteoblastic, or mixed
✓Complications — pathological fractures (code separately with M84.5x), hypercalcemia (E83.52), cord compression
✓Bone-modifying agent use — bisphosphonates, denosumab

Commonly Confused Codes

C79.52 — Secondary malignant neoplasm of bone marrow; bone metastases (C79.51) involve solid bone tissue, while marrow metastases (C79.52) infiltrate the hematopoietic tissue C40.0-C41.9 — Primary malignant neoplasm of bone; primary bone sarcomas are rare compared to metastatic bone disease M84.50-M84.58 — Pathological fracture in neoplastic disease; code separately when fracture occurs through metastatic bone lesion M89.70-M89.79 — Major osseous defect; not the same as metastatic bone destruction

Code Hierarchy

└C79Secondary malignant neoplasm of other and unspecified sites └C79.5Secondary malignant neoplasm of bone and bone marrow └C79.51Secondary malignant neoplasm of bone

└C79.51Secondary malignant neoplasm of bone