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Int J Clin Exp Pathol 2013;6(10):2192-2198

Original Article
Clinicopathological features of acute promyelocytic leukemia: an experience in one
institute emphasizing the morphological and immunophenotypic changes at the time of
relapse

Miyuki Yoshii, Mitsuaki Ishida, Takashi Yoshida, Hiroko Okuno, Ryota Nakanishi, Akiko Horinouchi, Keiko Hodohara, Hidetoshi Okabe

Department of Clinical Laboratory Medicine, Division of Diagnostic Pathology, Department of Hematology, Shiga University of Medical Science,
Shiga, Japan

Received July 26, 2013; Accepted August 28, 2013; Epub September 15, 2013; Published October 1, 2013

Abstract: Acute promyelocytic leukemia (APL) has two morphological variants, namely macrogranular (M3) and microgranular (M3v). M3v,
characterized by the presence of neoplastic promyelocytes with only sparse fine azurophilic granules, accounts for 10-25% of all APL and has
unique biological characteristics. Relapse occurs in approximately 20% of patients with APL. The morphological type of the leukemic cells at
relapse is usually identical with the primary disease, and only one case of morphological change at relapse has been reported. Here, we
analyzed the clinicopathological features of APL, including 4 relapsed cases emphasizing morphological changes at the time of relapse. The
unique finding of the present study is that 2 of 4 relapsed cases changed from M3 to M3v at relapse. The morphological features of these were
different in each case (one had blastic features and the other resembled monocytoid leukemic cells). Cytogenetic analyses revealed the
continued presence of t(15;17)(q22;q12) at the time of relapse and morphological change. Moreover, the immune phenotype of the leukemic
cells changed from CD2-/CD34- to CD2+/CD34+ at that time. These findings suggest that morphological change at relapse in APL may not be
a rare event, and that the leukemic cells can show variable morphological features at the time of relapse, which could result in misdiagnosis
as a different type of acute myeloid leukemia. Therefore, a comprehensive approach with emphasis on combined morphological,
immunophenotypic, and cytogenetic analyses is important for diagnosis and appropriate treatment of relapsed APL. (IJCEP1307045).

Keywords: Acute promyelocytic leukemia, macrogranular variant, microgranular variant, relapse

Address correspondence to: Dr. Mitsuaki Ishida, Department of Clinical Laboratory Medicine and Division of Diagnostic Pathology, Shiga
University of Medical Science, Tsukinowa-cho, Seta, Otsu, Shiga, 520-2192, Japan. Tel: +81-77-548-2603; Fax: +81-77-548-2407; E-mail:
mitsuaki@belle.shiga-med.ac.jp