When assigning and sequencing neoplasm codes in this scenario for metastatic prostate cancer to the lungs, you will need to know and apply the ICD-10-CM coding guidelines.

Xray showing metastatic prostate cancer to the lungs

Question:  A 67-year-old male patient with primary prostate cancer with metastasis to the left lung presents for a wedge resection of the lung.

Assign the ICD-10-CM codes.


  • C78.02, Secondary malignant neoplasm of left lung
  • C61, Malignant neoplasm of prostate

According to the ICD-10-CM coding guidelines, all malignant (and most benign) neoplasms are located in Chapter 2: Neoplasms (C00-D49).

Locate and Verify

First, let’s look up the code for the primary prostate cancer.

Looking in the ICD-10-CM coding manual in the Alphabetic Index under Cancer, it tells us to also see Neoplasm, by site, malignant.  Under Neoplasm, neoplastic, it refers us to also see the Table of Neoplasms. 

Going to the term “prostate (gland)” in the Table of Neoplasms, we can see that C61 is the proper code for Malignant Primary.

This can be verified in the Tabular as C61, Malignant neoplasm of prostate.

Review the instructional notes for any additional coding instructions to determine if any other codes need to be assigned. In this case, there is nothing else in the documentation to warrant any additional codes.

When we go to the Table of Neoplasms and look up Neoplasm, neoplastic, lung, we can see that C78.0- is the proper code for Malignant Secondary.

Verified in the Tabular, C78.02 refers to Secondary malignant neoplasm of left lung. 

Again, reviewing the instructional notes here indicates that there is nothing more to code based on what is in the documentation. 


Now that we have our two codes, we need to understand the coding guidelines before we can determine the proper sequencing of these two codes.

According to the ICD-10-CM Coding Guidelines:

When a patient is admitted because of a primary neoplasm with metastasis and treatment is directed toward the secondary site only, the secondary neoplasm is designated as the principal diagnosis even though the primary malignancy is still present.

Therefore, C78.02 is sequenced first, followed by C61.

Other Coding Guidelines

Other guidelines to keep in mind when coding for neoplasms as they apply to this scenario include:

In order to accurately code a neoplasm, it is necessary to review the medical record for the type of neoplasm (benign, in-situ, malignant, or of uncertain histologic behavior. 

The neoplasm table in the Alphabetic Index should be referenced first. However, if the histological term is documented, that term should be referenced first, rather than going immediately to the Neoplasm Table, in order to determine which column in the Neoplasm Table is appropriate. For example, if the documentation indicates “adenoma,” refer to the term in the Alphabetic Index to review the entries under this term and the instructional note to “see also neoplasm, by site, benign.” 

The table provides the proper code based on the type of neoplasm and the site. It is important to select the proper column in the table that corresponds to the type of neoplasm. The Tabular List should then be referenced to verify that the correct code has been selected from the table and that a more specific site code does not exist.

When coding for malignant neoplasms, any secondary (metastatic) sites should also be determined. 

When an encounter is for a primary malignancy with metastasis and treatment is directed toward the metastatic (secondary) site(s) only, the metastatic site(s) is designated as the principal/first-listed diagnosis. The primary malignancy is coded as an additional code.

Additional Information

Prostate Cancer

According to the Mayo Clinic, prostate cancer is one of the most common types of cancer in men. Although prostate cancer tends to grow slowly and usually remains confined to the prostate gland and requires little treatment, other types are aggressive and can spread quickly.

Prostate cancer typically spreads to the lymph nodes and the bones but may also spread to the lungs, liver, and brain, according to the Mayo Clinic. It is rare for prostate cancer to metastasize to the adrenal glands, breasts, eyes, kidney, muscles, pancreas, salivary glands, or spleen.

Wedge Resection

Although this coding exercise does not ask for a CPT code for the wedge resection of the lung, the National Cancer Insitute reports that a wedge resection is a surgical procedure performed to remove a triangle-shaped slice of tissue. It may be used to remove a tumor and a small amount of normal tissue around it.

A wedge resection of the lung specifically involves the removal of the lung lobe containing the cancer and a small amount of healthy tissue around it.

CPT codes for wedge resections of the lung are found in the Surgical Procedures on the Lungs and Pleura section of the CPT coding manual and are covered by CPT 32505-32507, 32665-32668.

This post has been updated to reflect the FY 2020 coding guidelines.