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Metastatic Prostate Cancer to the Lungs and Which is Principal?  

metastatic prostate cancer to the lungs

This post has been updated to reflect the FY 2022 coding guidelines.

Name That Code!

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 code(s).


Once you have assigned the code(s), read the information below. The answer is provided at the bottom of this post.

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

According to the FY 2022 ICD-10-CM Coding Guidelines, most benign and all malignant neoplasms are found in Chapter 2: Neoplasms (C00-D49) of the ICD-10-CM coding manual. Before coding a neoplasm, be sure to review the record to determine if the neoplasm is benign, in-situ, malignant, or of uncertain histologic behavior. If malignant, any secondary (metastatic) site should also be determined. 

Locate and Verify

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.  

Or we can look under Neoplasm, neoplastic – see also 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 then 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.

Metastatic Cancer to the Left Lung

Look in the Index under Neoplasm, neoplastic – see also Table of Neoplasms. Going to the term lung in the Table of Neoplasms, we can see that C78.0- is the proper code for Malignant Secondary.

In the Tabular, we can verify the correct code as:

C78.02, 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 FY 2022 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, Secondary malignant neoplasm of left lung, is sequenced first, followed by C61, Malignant neoplasm of prostate.

Other Coding Guidelines

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

“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.”

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 Institute 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 codes 32505-32507, and 32666-32668.

Answer:   C78.02, C61

** This post has been updated to reflect the FY 2022 coding guidelines. **

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