Pitfalls of the CD 45 / SSC Gating Method in the Diagnosis of Pediatric Hematological Malignancies

We performed flow cytometric analysis by using the CD45/SSC (CD45low/SSClow) gating method in 5 bone marrow (BM) samples with low percentages of blasts at the disease onset. The surface marker profiles in 4 cases (ALL 2, MDS 1, NHL 1) at the onset proved almost identical to those at the final diagnosis. In the last case, however, the patient was diagnosed as having neuroblastoma (CD45 negative) despite a B-cell precursor phenotype of BM cells gated by this method. To address issues on diagnostic disagreement in this case, we examined the surface markers of the BM populating gated by this method in 10 children with malignancy in complete remission. About 10% of the BM cells were gated to the CD45low/SSClow population, and their markers were CD10blight/CD19bright/HLA-DRbright/CD20dim/CD33dim/CD34dim, which was consistent with the phenotype of the B-cell precursors. Although the surface marker analysis using the CD45/SSC gating method is useful for the diagnosis of pediatric hematological malignancies, the results should be carefully interpreted with an understanding of the usefulness and the pitfalls of this methodology. 要 旨CD45/SSC(CD45low/SSClow)gating法 を用 いて,病 初期 に骨髄 中の芽球比率 が低 か った小児悪性 腫 瘍5症 例 において腫瘍細胞 の表面抗原 を解析 した.4症 例(ALL 2例,MDS 1例,NHL 1例)は 初診 時 と 最終診 断時 にお ける解析 結果が一致 した.し か し,本 法 でB細 胞型 悪性 リンパ腫 の骨髄 浸潤 とした1症 例 の 最終診 断 はCD45陰 性の神経芽腫 であ った.本 症例 で診断が異 なった原因 を明 らかにす るた め,完 全寛 解中 の小児悪性 腫瘍患者10症 例 の骨髄検体 で,CD45low/SSClow分 画にgatingさ れる細胞 集団 の表面抗 原 を解 析 した.約10%の 骨髄 細胞 がgatingさ れ,CD10,CD19,HLA-DRが 強陽性,CD20,CD34,CD33が 弱陽性 のB-cell precursorの 表現型 を示 した.本 法 を用いた表面抗原解析 は,造 血 器悪性腫瘍 の診 断 に有益 な検 査法 で あるが,そ の有用性 と危険性 を よく理解す る必要 があ る.