ICD-10 Code C96.29 – Other malignant mast cell neoplasm (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C96.29 – Other malignant mast cell neoplasm
What it is
C96.29 identifies a malignant neoplasm of mast cells that does not fit a more specific ICD-10-CM mast cell category. It is used for documented malignant mast cell disease when the record does not name a different code.
Clinical signs
Clinical features vary; refer to documentation. Mast cell neoplasms may present with skin lesions, flushing, itching, abdominal complaints, or findings of systemic involvement, but you should code only what the clinician documents.
When to use this code
Use C96.29 when the provider documents a malignant mast cell neoplasm and no more specific subtype is stated. It is appropriate for confirmed malignant mast cell disease in the chart, including cases described as other or unspecified malignant mast cell neoplasm. If the record instead names a different mast cell disorder, check documentation.
Do not use for
Do not use this code for benign mast cell conditions, mastocytosis without malignancy, or uncertain findings that are not confirmed as malignant. Check documentation if the diagnosis is a different hematologic or skin disorder.
Coding tip
Code only when the provider clearly documents malignancy; if the wording is vague, query for clarification before assigning C96.29.