[Differences in the bone marrow histopathology between pediatric acquired aplastic anemia and refractory cytopenia of childhood].

Objective: To study the differences in the bone marrow histopathology between acquired aplastic anemia (AAA) in children and refractory cytopenia of childhood (RCC) to facilitate their diagnoses and differential diagnosis. Methods: The clinical data and bone marrow biopsies of the RCC and AAA cases diagnosed from January 2008 to December 2018 in Xinhua Hospital, Shanghai Jiaotong University School of Medicine and Shanghai Children's Medical Center affiliated to Shanghai Jiaotong University School of Medicine were analyzed. Results: A total of 71 AAA and 79 RCC cases were analyzed. There were 52 males and 19 females, age ranged 1.0-15.0 years (median, 8.9 years) in the AAA group, and 53 males and 26 females, age ranged 0.5-16.0 years (median, 5.0 years) in the RCC group. All the biopsy specimens of AAA patients had severe hypocellularity; the cellularity of 88.7% (63/71) specimens was under 5.0%, and 11.3%(8/71) was 5%-24%. None of the AAA specimens showed any dysplastic change. All the biopsy specimens of RCC patients had hypocellularity, including 94.9%(75/79) of the specimens with a cellularity of 5%-50%. All of the RCC specimens showed a patchy distribution of hematopoiesis. A dysplastic change of erythroid cells and micromegakaryocytes was found in 40.5% (32/79) and in 60.8% (48/79) of the RCC cases, respectively. Conclusions: The degree of hypocellularity, the distribution pattern of hematopoiesis, the cell composition and localization of erythroid cell clusters and the appearance of micromegaryocytes could help the diagnosis and differential diagnosis of AAA and RCC.