Correct Coding of Skin Lesions

Procedures on skin can be some of the most difficult to code because of the many categories of lesions, location of lesions, number of lesions, diameter of lesions, incomplete documentation, and the terminology used by physicians. Here are some guidelines for correct coding of skin lesions:

Lesion Categories

Lesions are categorized as skin tags, warts, neoplasms, or masses/lumps (cyst, tumor). First consult the ICD-10-CM Index for the term documented. For example, cysts are categorized to the tissue in which they are found. If the documentation shows the cyst or lesion was removed from skin tissue, find the term Cyst, followed by the sub term skin, followed by the type of cyst.

Neoplasms can be either malignant, benign, uncertain behavior, or unspecified behavior. Malignant lesions can be primary, the first site of malignancy; secondary, site where primary malignancy has metastasized or “spread”; and carcinoma in situ, an early form of cancer defined by the absence of invasion of tumor cells into the surrounding tissue.

Benign lesions are not malignant and do not metastasize or “spread” to other parts of the body. Benign lesions look similar to the tissue where the lesion originated and grow slowly. Though benign lesions are not cancerous, they may cause problems because of their location and often there are multiple benign lesions which can cause adverse effects on the body.

Lesions of uncertain behavior are categorized as uncertain when the lesion has not been identified as malignant or benign. The physician needs to document uncertain behavior in order for this category to be used. Usually, uncertain behavior is documented on preoperative diagnoses and documentation prior to surgical removal and submission to pathology. The pathologist will then clarify whether the lesion is benign or malignant.

Lesions of unspecified behavior are lesions where there is absence of documentation of benign, malignant, or uncertain. This is the “catch all” category and should be used as little as possible.

Location of skin lesions

Skin tissue has three main layers which are divided into sub layers. The location of the skin lesion in the skin layers will determine the code category that is used.

The epidermis is the outermost main layer of skin. This layer includes the stratum corneum (horny sub layer), followed by the keratinocytes (squamous cells sub layer), and finally the basal sub layer. The horny sub layer is continuously shed and prevents foreign substances and loss of fluid from the body. The squamous cells sub layer lies just beneath the horny sub layer. The basal sub layer is the deepest sub layer of the epidermis. Throughout the epidermis are melanocytes, specialized cells which produce melanin (skin pigment).