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Q14. 肥大細胞 mast cell 病變或稱 systemic mastocytosis 有許多類型及特徵，下列敘述何者正確？ (1) Total serum tryptase 上升，>20ng/ml (2) Mast cell markers are CD117+, also aberrant expression CD25+, CD2, CD30 (3) 最重要的基因突變為 KIT D816V (4) 常伴有皮膚病變 urticaria pigmentosa, PB 中多見 basophilia, 少見 anemia 此型預後佳，如 SM-CMML, 預後比照 low risk MDS

  • (A) 1,2,3 are correct
  • (B) 1,3 are correct
  • (C) 2,4 are correct
  • (D) only 4 is correct
  • (E) all of the above
點此顯示正解

(A) 1,2,3 are correct

詳解

Explanation of Answer (A): Statements 1, 2, and 3 are Correct

Statement (1) is TRUE: Total serum tryptase >20 ng/mL is a minor diagnostic criterion for systemic mastocytosis according to both WHO 2022 and ICC 2022 classifications1234. The diagnostic criteria require either 1 major + 1 minor criterion, or ≥3 minor criteria to establish the diagnosis of SM.

Statement (2) is TRUE: Mast cells in SM are CD117+ (KIT+) and aberrantly express CD25 and/or CD2, which constitute a minor diagnostic criterion1234. CD30 is increasingly recognized as an aberrant marker, particularly in cases with well-differentiated round cell morphology that may be negative for CD25 and CD2123. The ICC and WHO criteria explicitly list aberrant expression of CD2, CD25, and/or CD30 as a minor criterion.

Statement (3) is TRUE: KIT D816V is the key driver mutation in systemic mastocytosis, present in >90% of adult SM cases235. Detection of KIT D816V or other activating KIT mutations in bone marrow, peripheral blood, or other extracutaneous organs is a minor diagnostic criterion1234.

Why Statement (4) is FALSE: SM-AHN/SM-CMML Has POOR Prognosis

Statement (4) is FALSE because SM with associated hematologic neoplasm (SM-AHN), particularly SM-CMML, carries a POOR prognosis, not a favorable one comparable to low-risk MDS:

Survival data for SM-AHN/SM-CMML: - Overall median survival in SM-AHN: 24 months7[9][10] - SM-CMML specifically: median survival only 15 months7[9][10] - SM-MDS: 13 months median survival7[9][10] - SM-AML: 11 months median survival7[9][10]

In contrast, low-risk MDS typically has median survival measured in years (often 5+ years), making the comparison in statement (4) completely incorrect.

ICC 2022 reclassification: The ICC now designates this category as SM-AMN (SM with associated myeloid neoplasm) rather than SM-AHN, recognizing the shared clonal origin with myeloid but not lymphoid neoplasms7[^8]. SM-AMN with myeloid neoplasms has median survival of approximately 2 years, while SM with associated lymphoid neoplasms (SM-ALN) has significantly better survival of 8.1 years[^8].

Additional context on statement (4): - While urticaria pigmentosa (cutaneous mastocytosis) is common in SM, peripheral basophilia is not a typical feature - Anemia is actually common in advanced SM, particularly SM-AHN, and is part of prognostic scoring systems - The characterization of SM-CMML as having "good prognosis similar to low-risk MDS" is the critical error that makes statement (4) false

SM-C: Systemic Mastocytosis: Diagnostic Criteria for Systemic Mastocytosis — NCCN Guidelines® — Systemic Mastocytosis p. 17 (v2.2026)

Figure 2: Diagnostic algorithm for systemic mastocytosis. ICC indicates International Consensus Classification; WHO, World Health Organization; MC, mast cells; SM, systemic mastocytosis; AMN, associated myeloid neoplasm; ISM, indolent SM; MCL, mast cell leukemia; SSM, smoldering SM; and ASM, aggressive SM.

詳解 · 中文翻譯

答案 (A) 解釋：陳述 1、2 和 3 正確

陳述 (1) 真實：血清總 tryptase >20 ng/mL 根據 WHO 2022 和 ICC 2022 分類是 系統性肥大細胞增多症的次要診斷標準1234。診斷標準要求 1 個主要 + 1 個次要標準，或 ≥3 個次要標準以確立 SM 的診斷。

陳述 (2) 真實：SM 中的肥大細胞為 CD117+（KIT+） 且異常表達 CD25 和/或 CD2，構成次要診斷標準1234。CD30 日漸被認識為異常標誌物，特別是在可能對 CD25 和 CD2 陰性的良分化圓形細胞形態學病例中123。ICC 和 WHO 標準明確將 CD2、CD25 和/或 CD30 的異常表達列為次要標準。

陳述 (3) 真實：KIT D816V 是系統性肥大細胞增多症的關鍵驅動突變，存在於 >90% 的成人 SM 病例中235。在骨髓、周邊血液或其他結外器官中檢測 KIT D816V 或其他激活 KIT 突變是次要診斷標準1234。

為何陳述 (4) 假：SM-AHN/SM-CMML 預後差

陳述 (4) 假，因為伴隨血液腫瘤的系統性肥大細胞增多症（SM-AHN），特別是 SM-CMML，預後差，不是與低風險 MDS 相當的有利預後：

SM-AHN/SM-CMML 的生存數據： - SM-AHN 中的整體中位生存：24 個月7[9][10] - SM-CMML 特別地：中位生存只有 15 個月7[9][10] - SM-MDS：13 個月中位生存7[9][10] - SM-AML：11 個月中位生存7[9][10]

相比之下，低風險 MDS 通常中位生存以 年 計（常 5+ 年），使陳述 (4) 中的比較完全不正確。

ICC 2022 重新分類：ICC 現在將此類別指定為 SM-AMN（伴隨骨髓腫瘤的 SM） 而非 SM-AHN，認識與骨髓但非淋巴腫瘤的共享克隆來源7[^8]。具有骨髓腫瘤的 SM-AMN 的中位生存約為 2 年，而伴隨相關淋巴腫瘤的 SM（SM-ALN）的生存顯著更好，為 8.1 年[^8]。

陳述 (4) 的額外背景： - 雖然蕁麻疹色素沉著症（皮膚肥大細胞增多症）在 SM 中常見，但周邊嗜鹼粒細胞增多症不是典型特徵 - 貧血在晚期 SM 中實際上很常見，特別是 SM-AHN，且是預後評分系統的一部分 - 將 SM-CMML 描述為具有「與低風險 MDS 相似的良好預後」是使陳述 (4) 假的關鍵誤導

參考文獻 (AMA)

  1. National Comprehensive Cancer Network. Systemic Mastocytosis. https://www.nccn.org/professionals/physician_gls/pdf/mastocytosis.pdf#page=17. ↩↩↩↩↩↩↩↩

  2. Wang SA, Orazi A, Gotlib J, et al. The International Consensus Classification of Eosinophilic Disorders and Systemic Mastocytosis. American Journal of Hematology. 2023;98(8):1286-1306. doi:10.1002/ajh.26966. PMID:37283522. ↩↩↩↩↩↩↩↩↩↩

  3. Pardanani A. Systemic Mastocytosis in Adults: 2023 Update on Diagnosis, Risk Stratification and Management. American Journal of Hematology. 2023;98(7):1097-1116. doi:10.1002/ajh.26962. PMID:37309222. ↩↩↩↩↩↩↩↩↩↩

  4. Theoharides TC, Valent P, Akin C. Mast Cells, Mastocytosis, and Related Disorders. The New England Journal of Medicine. 2015;373(2):163-72. doi:10.1056/NEJMra1409760. PMID:26154789. ↩↩↩↩↩↩

  5. Pardanani A. Systemic Mastocytosis in Adults: 2021 Update on Diagnosis, Risk Stratification and Management. American Journal of Hematology. 2021;96(4):508-525. doi:10.1002/ajh.26118. PMID:33524167. ↩↩

  6. Pardanani A. Systemic Mastocytosis in Adults: 2019 Update on Diagnosis, Risk Stratification and Management. American Journal of Hematology. 2019;94(3):363-377. doi:10.1002/ajh.25371. PMID:30536695. ↩

  7. Aperna F, Abdelmagid MG, Kumar M, et al. Systemic Mastocytosis in 910 Patients: Prognostic Contribution of the International Consensus Classification in the Context of the Mayo Alliance Prognostic System. American Journal of Hematology. 2025;100(9):1566-1576. doi:10.1002/ajh.27764. PMID:40607735. ↩↩↩↩↩↩↩↩↩↩

Slide annotations

(High risk)

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