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Question: Our lab performed a biopsy on tissue samples taken from a female patient’s upper inner and upper outer left-breast quadrants. The results were positive for breast cancer. What is the correct ICD-10-CM coding for this?

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Answer: The key to correctly coding this scenario is knowing whether the patient has two distinct lesions or if the cancer is overlapping the two biopsy sites. This, in turn, depends on whether the surgeon submits the lesions together in one container without distinction or as two separately identified specimens. The distinction is important for both procedure and diagnosis coding.

When the specimens indicate malignancies in separate or noncontiguous sites: The general guidelines accompanying ICD-10-CM Chapter 2 tell you that “for multiple neoplasms of the same site that are not contiguous such as tumors in different quadrants of the same breast, codes for each site should be assigned.” Based on that instruction, you would report two distinctly identified specimens in this case as C50.212 (Malignant neoplasm of upper-inner quadrant of left female breast) and C50.412 (Malignant neoplasm of upper-outer quadrant of left female breast).

When the specimens indicate a malignancy in a contiguous, or overlapping, site: Coding for a single specimen that overlaps two quadrants is different. The same ICD-10-CM guideline states, “a primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 (‘overlapping lesion’), unless the combination is specifically indexed elsewhere.” That means if the op report documents that the lesion is overlapping the upper inner and upper outer quadrant, the pathology report should reflect that, and you would report just one code for this case: C50.812 (Malignant neoplasm of overlapping sites of left female breast).

If the pathology report is not clear regarding the site or sites from which the tissue samples were taken from the patient’s breast, you would do well to query your pathologist.

Bruce Pegg, BA, MA, CPC, CFPC, Managing Editor, AAPC