Carcinoma in situ of skin of other and unspecified parts of face

This code signifies the presence of non-invasive malignant cells confined to the epidermis (carcinoma in situ) affecting the skin of the face, excluding the eyelid. It represents a pre-invasive form of squamous cell carcinoma or basal cell carcinoma, where the abnormal cells have not yet penetrated the basement membrane.

Apply this code when documentation specifies carcinoma in situ of the skin on facial areas such as the forehead, cheek, nose, or chin. It is appropriate when a biopsy confirms the diagnosis and explicitly states "in situ" or "intraepidermal carcinoma" without evidence of invasion.

• Differentiate from invasive carcinoma of the skin of the face, which would require a code from the 173.x series.
• Ensure the documentation clearly specifies "in situ" and the facial location; avoid using for unspecified skin lesions.
• Do not use for carcinoma in situ of the eyelid, which has a more specific code.