ICD-10-CM Code C96.21

Aggressive systemic mastocytosis

Version 2021 Billable Code

Valid for Submission

C96.21 is a billable code used to specify a medical diagnosis of aggressive systemic mastocytosis. The code is valid for the fiscal year 2021 for the submission of HIPAA-covered transactions. The ICD-10-CM code C96.21 might also be used to specify conditions or terms like aggressive lymphadenopathic mastocytosis with eosinophilia or aggressive systemic mastocytosis or malignant white blood cell disorder or systemic mast cell disease or systemic mast cell disease.

Short Description:Aggressive systemic mastocytosis
Long Description:Aggressive systemic mastocytosis

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code C96.21 are found in the index:


The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Aggressive lymphadenopathic mastocytosis with eosinophilia
  • Aggressive systemic mastocytosis
  • Malignant white blood cell disorder
  • Systemic mast cell disease
  • Systemic mast cell disease

Clinical Information

  • MASTOCYTOSIS SYSTEMIC-. a group of disorders caused by the abnormal proliferation of mast cells in a variety of extracutaneous tissues including bone marrow liver spleen lymph nodes and gastrointestinal tract. systemic mastocytosis is commonly seen in adults. these diseases are categorized on the basis of clinical features pathologic findings and prognosis.

Replacement Code

C9621 replaces the following previously assigned ICD-10 code(s):

  • C96.2 - Malignant mast cell neoplasm
  • C96.2 - Malignant mast cell tumor

Convert C96.21 to ICD-9

  • 202.60 - Mlg mast unsp xtrndl org (Approximate Flag)
  • 202.61 - Mal mastocytosis head (Approximate Flag)
  • 202.62 - Mal mastocytosis thorax (Approximate Flag)
  • 202.63 - Mal mastocytosis abdom (Approximate Flag)
  • 202.64 - Mal mastocytosis axilla (Approximate Flag)
  • 202.65 - Mal mastocytosis inguin (Approximate Flag)
  • 202.66 - Mal mastocytosis pelvic (Approximate Flag)
  • 202.67 - Mal mastocytosis spleen (Approximate Flag)
  • 202.68 - Mal mastocytosis mult (Approximate Flag)

Code Classification

  • Neoplasms (C00–D48)
    • Malignant neoplasms of lymphoid, hematopoietic and related tissue (C81-C96)
      • Oth & unsp malig neoplm of lymphoid, hematpoetc and rel tiss (C96)

Code History

  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021