Neoplasm of unspecified behavior of breast

This code signifies a breast tumor where the pathologist has not yet determined if it is benign or malignant. It is used when the behavior of the neoplasm (e.g., whether it is cancerous or non-cancerous) is unknown or pending further investigation. This typically represents an initial finding or a lesion requiring further diagnostic workup.

Use this code when diagnostic studies (e.g., biopsy results) are inconclusive regarding the malignancy of a breast lesion, or when the pathology report explicitly states "neoplasm of unspecified behavior." It is appropriate for initial encounters where a breast mass is identified but its nature is not yet definitively classified as benign or malignant. Documentation must clearly indicate the breast as the primary site and the unspecified behavior.

• Do not use this code if the pathology report definitively identifies the neoplasm as benign (e.g., fibroadenoma) or malignant (e.g., invasive ductal carcinoma).
• Remember the Excludes1 note: never code this with D49.2 (neoplasm of unspecified behavior of skin of breast).
• This code is often a temporary code, to be replaced with a more specific code once definitive pathology results are available.