Observe National Breast Cancer Awareness Month With Increased Neoplasm Coding Know-How

ICD-10 coding for breast cancer

October is National Breast Cancer Awareness Month. You may be familiar with the statistic that roughly one in eight women will develop invasive breast cancer. For men, the lifetime risk is about 1 in 1,000.

The expansion of male breast cancer diagnosis codes to be as specific to site as female breast cancer codes was one of the important changes oncology coders had to learn back when ICD-9 changed to ICD-10. Here are some documentation tips to help with breast cancer coding and a bonus tip on ICD-10-CM 2018 changes to breast lump coding.

Know Site, Patient’s Sex, and Side of Body for C50.-

You’ll find ICD-10-CM codes for both female and male patients in C50.- (Malignant neoplasm of breast).

Site: The fourth character defines the site:

  • 0, nipple and areola
  • 1, central portion
  • 2, upper-inner quadrant
  • 3, lower-inner quadrant
  • 4, upper-outer quadrant
  • 5, lower-outer quadrant
  • 6, axillary tail
  • 8, overlapping sites
  • 9, unspecified site.

Sex: The fifth character identifies the patient as female or male.

Side: The sixth character indicates which breast the neoplasm is in: right, left, or unspecified.

Know Where to Go for Additional Insights

Category C50.- includes connective tissue of breast and Paget’s disease of the breast and nipple, the official code set states. Another note at the category level instructs you to identify estrogen receptor status (Z17.0, Z17.1). But if you’re coding a neoplasm of the skin, you’re in the wrong place. An Excludes1 note points you to C44.501, C44.511, C44.521, and C44.591 for skin cancer of the breast.

Tip: To ensure accurate coding, you should read the ICD-10 Official Guidelines for Coding and Reporting. Focus on Section I.C.2, which covers the neoplasms chapter of ICD-10-CM. You’ll discover important rules like how to sequence codes based on the type of encounter, the presence of secondary tumors, and complications documented. That section also explains that you should use a code from history category Z85.- “When a primary malignancy has been previously excised or eradicated from its site and there is no further treatment directed to that site and there is no evidence of any existing primary malignancy.” Code Z85.3 (Personal history of malignant neoplasm of breast) applies when reporting history of a diagnosis that falls under C50.-.

Look for New ‘Lump in Breast’ Codes

In some cases, you may need to code a case before a definitive pathology report comes in. The only information you have is that the patient has a lump in the breast. ICD-10 2018, effective Oct. 1, added site and side specificity to codes for unspecified lump in the breast. Here are the main pointers:

  • In rare cases when you don’t have much to go on, you may have to resort to N63.0 (Unspecified lump in unspecified breast). Note that N63.0 is a complete, reportable code.
  • For the right side, use a code from subcategory N63.1- (Unspecified lump in right breast).
  • For the left side, you’ll instead use a code from subcategory N63.2- (Unspecified lump in left breast).
  • For both N63.1- and N63.2-, the fifth character identifies the quadrant. The digits used for quadrants differ from those in the C50.- category shown in the first bullet list above. Here is what you will see for N63.1- and N63.2-:
    • 0, unspecified
    • 1, upper outer
    • 2, upper inner
    • 3, lower outer
    • 4, lower inner.
  • You also have subcategories N63.3- (Unspecified lump in axillary tail) and N63.4- (Unspecified lump in breast, subareolar). The fifth characters for these codes identify right breast (1) and left breast (2).

What About You?

Do you have any tips for coders who are new to coding breast cancer diagnoses? What is the most useful thing you have learned from the Official Guidelines?


Deborah works on a wide range of TCI SuperCoder projects, researching and writing about coding, as well as assisting with data updates and tool development for our online coding solutions. Since joining TCI in 2004, she’s covered the ins and outs of coding for radiology, cardiology, oncology and hematology, orthopedics, audiology, and more.

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