Abstract：
\"Lineage switch\" is term described when leukemic cells on relapse exhibit a new phenotype, where losses of one lineage defining markers with simultaneous gain of another lineage defining markers occur. Relapse of acute leukemia is although a very common event, lineage switch occurs and reported very rarely in such cases. The pathogenesis involved in this phenomenon remains unclear; however plasticity of hematopoietic progenitor affected by intrinsic and extrinsic environmental cues can be a possible explanation. In most of the cases at the time of relapse conversion of B-acute lymphoblastic leukemia (ALL) to acute myeloid leukemia (AML) occurs. Here, we presented an unusual case of 10 year old boy with AML switched to T-ALL upon relapse, which is very rare and not well documented till date in literature. The diagnosis was further supported by morphologic, cytochemistry and flowcytometric immunophenotyping (FCM-IPT). Prognosis and survival of such cases remains poor even by the use of standard chemotherapy.
摘要：
“谱系转换”是指白血病细胞在复发时表现出新的表型，其中一个谱系定义标记的损失与另一个谱系定义标记的同时增益发生。急性白血病复发虽然是很常见的事件,在这种情况下，谱系转换发生并且很少报道。这种现象的发病机理尚不清楚；然而，受内在和外在环境线索影响的造血祖细胞的可塑性可能是一种可能的解释。在复发时的大多数情况下，都会发生B急性淋巴细胞白血病（ALL）向急性髓细胞性白血病（AML）的转化。这里,我们提出了一个不寻常的10岁男孩AML复发后转换为T-ALL，这是非常罕见的，直到文献中没有很好的记载。诊断得到形态学的进一步支持，细胞化学和流式细胞术免疫表型（FCM-IPT）。即使使用标准化疗，此类病例的预后和生存率仍然很差。
