Final answer:
The ICD-10 code for secondary malignant neoplasm of the bone and bone marrow is C78.01, which is used when lung cancer has metastasized to the iliac bone. The primary lung cancer would also need an appropriate ICD-10 code.
Step-by-step explanation:
The ICD-10 code for a patient with lung cancer that has metastasized to the iliac bone causing acute hip pain would be C78.01 for the secondary malignant neoplasm of the bone and bone marrow. Additionally, since the primary diagnosis is lung cancer, you would also report the ICD-10 code for the primary neoplasm, which would be determined based on the specific type of lung cancer the patient has (for example, C34.90 for unspecified part of unspecified bronchus or lung). Remember, when coding for metastasis, both the primary and secondary sites should be coded.
It's essential to provide accurate coding for the patient's condition because it influences treatment decisions and the management of their healthcare.