Pathology/Lab Coding Alert

Question: The pathologist examined a skin lesion removed from the patient's nose identified as actinic keratosis. The path report diagnosis reads "actinic keratosis/squamous cell carcinoma in itu extending to lateral margin." What is the proper ICD-9 code?

Texas Subscriber

Answer: The correct ICD-9 code for the lesion is 232.3 (Carcinoma in situ of skin of other and unspecified parts of face). Don't report the diagnosis as actinic keratosis (702.0, Other dermatoses, Actinic keratosis).

Here's why: You should code the condition based on the pathologist's findings, not on the surgeon's lesion description, which is necessarily less specific. The confusion stems from the fact that the pathology report includes both descriptors.

But the carcinoma in situ is a more specific diagnosis based on pathologic findings.

Using the ICD-9 Index to Diseases and Injuries, you'll see that squamous cell intraepidermal refers to neoplasm, skin, in situ. Using the neoplasm table, the "Ca in situ" column for skin of nose (external) refers you to 232.3. When you turn to 232.3 in the ICD-9 Tabular List, you'll find no "excludes" notes that preclude the diagnosis.

Contrast: If you look up "keratosis, actinic," the ICD-9 index will refer you to 702.0. Note that the "excludes" note for 702 (Other dermatoses) leaves out carcinoma in situ (232.0-232.9). That means you cannot use this code for the diagnosis your pathologist listed in the report.