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SEER Inquiry System - Report
Produced: 03/12/2026 5:29 PM
Question 20190017
Inquiry Details
References:
WHO Class Hem & Lymph Tumors, 62-69. 4th ed.
Question:
Reportability--Heme & Lymphoid Neoplasms: The term indolent systemic mastocytosis is listed in the 2018 ICD-O-3 Histology Update table with borderline behavior (9741/1). However, smoldering systemic mastocytosis is listed in the Hematopoietic and Lymphoid Database (Heme DB) as an alternate name for histology 9741/3. Are smoldering systemic mastocytosis and indolent systemic mastocytosis synonymous? If so, should smoldering systemic mastocytosis also be removed from the Heme DB alternate names listing? See Discussion.
Discussion:
In addition to the issue mentioned above, there is a SINQ answer that conflicts with the 2018 ICD-O-3 Histology Update table. SINQ 20130134 indicates indolent systemic mastocytosis is reportable for cases diagnosed 2010 and forward. There is no date restriction indicating the SINQ note applies only for cases diagnosed 2010-2017. Since indolent systemic mastocytosis was changed to borderline (9741/1) for diagnosis year 2018+, should the diagnosis year range be updated for this SINQ answer?
Answer:
Smoldering systemic mastocytosis is reportable, 9741/3. Indolent systemic mastocytosis is not reportable as of cases diagnosed 2018, 9741/1.
Smoldering systemic mastocytosis and indolent systemic mastocytosis are not synonymous. Smoldering differs from indolent based on diagnostic criteria and burden of disease; indolent is low whereas smoldering is high burden of disease that can progress to aggressive systemic mastocytosis or mast cell leukemia.
We will update SINQ 20130134.
