Other mast cell neoplasms of uncertain behavior

This code signifies a mast cell neoplasm that is not definitively benign or malignant, falling into the category of uncertain behavior. These are abnormal growths of mast cells, which are immune cells, that do not meet the criteria for a specific mastocytosis or a clearly malignant mast cell sarcoma.

Use this code when pathology reports indicate a mast cell proliferation that is atypical but lacks clear features of malignancy, or when the behavior cannot be definitively classified. Documentation should clearly state "mast cell neoplasm of uncertain behavior" or similar terminology, ruling out specific mastocytosis types or overt malignancy.

• Distinguish carefully from D47.01 (cutaneous mastocytosis) and D47.02 (systemic mastocytosis), which are specific forms of mast cell disease.
• Avoid using this code if a definitive diagnosis of a malignant mast cell tumor (e.g., C96.2) or a benign mast cell lesion is established.
• Ensure the pathology report supports the "uncertain behavior" aspect; do not assume based on clinical presentation alone.