C96.21 is the authoritative medical code for Aggressive systemic mastocytosis. This classification is used in medical billing and clinical recording to specify the clinical criteria for aggressive systemic mastocytosis (ICD-10-CM C96.21), ensuring healthcare documentation aligns with 2026 federal coding standards.
Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.
Official Registry Overview & Definition
Aggressive systemic mastocytosis is a billable ICD-10-CM diagnosis code C96.21. Excludes1 (not coded here): indolent mastocytosis D47.02; mast cell leukemia C94.30; mastocytosis congenital cutaneous Q82.2; personal history of other malignant neoplasms of lymphoid, hematopoietic and related tissues Z85.79. Excludes2 (not included here): Kaposi's sarcoma of lymph nodes C46.3; secondary and unspecified neoplasm of lymph nodes C77.-; secondary neoplasm of bone marrow C79.52; secondary neoplasm of spleen C78.89.
Official Tabular Instructional Notes
Sequencing, inclusion, and exclusion notes published for C96.21 in the official ICD-10-CM tabular list.
Excludes1 — Not Coded Here
Conditions that can never be reported with this code; the two are mutually exclusive.
- indolent mastocytosis D47.02
- mast cell leukemia C94.30
- mastocytosis congenital cutaneous Q82.2
- personal history of other malignant neoplasms of lymphoid, hematopoietic and related tissues Z85.79
Excludes2 — Not Included Here
Conditions not covered by this code, but which may be reported alongside it when both are present.
- Kaposi's sarcoma of lymph nodes C46.3
- secondary and unspecified neoplasm of lymph nodes C77.-
- secondary neoplasm of bone marrow C79.52
- secondary neoplasm of spleen C78.89
Frequently Asked Questions (FAQ) & Clinical Guidance
What can't be coded together with C96.21?
Per official ICD-10-CM Excludes1 instructions, C96.21 must not be reported together with: indolent mastocytosis (D47.02); mast cell leukemia (C94.30); mastocytosis (congenital) (cutaneous) (Q82.2); personal history of other malignant neoplasms of lymphoid, hematopoietic and related tissues (Z85.79).
Can C96.21 be reported alongside related conditions?
Per official ICD-10-CM Excludes2 instructions, C96.21 and the following are not considered part of each other and may both be reported when both conditions are present: Kaposi's sarcoma of lymph nodes (C46.3); secondary and unspecified neoplasm of lymph nodes (C77.-); secondary neoplasm of bone marrow (C79.52); secondary neoplasm of spleen (C78.89).
Nearest Codes in This Family
Official ICD-10-CM classifications closest to C96.21 in its code family, with their registry titles.
- C96 — Other and unspecified malignant neoplasms of lymphoid, hematopoietic and related tissue
- C96.0 — Multifocal and multisystemic (disseminated) Langerhans-cell histiocytosis
- C96.2 — Malignant mast cell neoplasm
- C96.20 — Malignant mast cell neoplasm, unspecified
- C96.22 — Mast cell sarcoma
- C96.29 — Other malignant mast cell neoplasm
- C96.4 — Sarcoma of dendritic cells (accessory cells)
- C96.5 — Multifocal and unisystemic Langerhans-cell histiocytosis
- C96.6 — Unifocal Langerhans-cell histiocytosis
- C96.9 — Malignant neoplasm of lymphoid, hematopoietic and related tissue, unspecified
View all 12 codes in the C96 family
Indexed Clinical Terms (1)
Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code.
- Mastocytosis, aggressive systemic