眼窩腫瘍精査を契機として急性骨髄性白血病の再発が判明した1例

A case of acute myeloid leukemia relapse detected through the investigation of an orbital lesion

要約　目的：急性骨髄性白血病（AML）は通常，全身症状や血液検査異常を契機に診断され，眼窩腫瘍から診断に至ることは稀である。今回筆者らは，眼窩腫瘍の精査を契機にAML再発が判明した症例を経験したので報告する。

症例：症例は44歳，男性。4年前から原発性骨髄線維症で経過観察され，18か月前に末梢血芽球割合が上昇しAMLと診断され，同種造血幹細胞移植および臍帯血移植を受けた。1か月前から右上眼瞼の浮腫と腫瘤を自覚し，九州大学病院眼科を初診した。右上眼瞼内側に可動性良好な皮下腫瘤が触知され，MRIでは右眼窩内上方から内側にかけてT1強調画像，T2強調画像ともに脳実質と同程度の信号強度で，ガドリニウムにより均一に造影される17×10×15mmの腫瘤を認めた。経皮生検を施行したところ，切除組織はHE染色では核濃染像を伴い多形性に富んだ核と，透明な空胞を伴った細胞質をもつ大小不同の細胞がシート状に配列していた。免疫染色を行うと，ミエロペルオキシダーゼ，c-kitが陽性で骨髄肉腫と診断し，AMLの髄外再発と判断した。根治的治療は困難であり，緩和目的に放射線照射とベネトクラクス＋アザシチジン併用療法を施行して腫瘤は縮小したが，最終的に黄色ブドウ球菌由来の敗血症により，初診から4か月後に死亡した。

結論：本症例のように白血病の既往がある眼窩腫瘍は，白血病の再発を念頭に置いて精査する必要がある。

Abstract　Purpose：Acute myeloid leukemia（AML） is typically diagnosed based on systemic symptoms or abnormalities in blood tests；however, the initial presentation of an orbital tumor is rare. Here, we report a case in which AML relapse was detected during the evaluation of an orbital mass.

Case：A 44-year-old man had been under observation for primary myelofibrosis for four years. Eighteen months earlier, he was diagnosed with AML due to a marked increase in peripheral blood blasts and subsequently underwent allogeneic hematopoietic stem cell transplantation followed by cord blood transplantation. One month before presentation, he noticed swelling and a mass in his right upper eyelid and was referred to the Department of Ophthalmology at Kyushu University. Upon examination, a mobile subcutaneous mass was palpable on the medial side of the right upper eyelid. Orbital Magnetic Resonance Imaging revealed a 17×10×15 mm homogeneously enhancing mass extending from the superior to the medial orbit, with a signal intensity similar to that of the brain parenchyma in T1- and T2-weighted images. Percutaneous biopsy was performed. Hematoxylin and eosin staining revealed a sheet-like proliferation of pleomorphic cells with hyperchromatic nuclei and clear cytoplasmic vacuoles. Immunohistochemical staining was positive for myeloperoxidase and c-kit, leading to a diagnosis of myeloid sarcoma. Therefore, the lesion was interpreted as an extramedullary relapse of the AML. As curative treatment was not feasible, palliative radiation therapy combined with venetoclax and azacitidine was initiated. Although the tumor showed partial regression, the patient ultimately died from Staphylococcus aureus-induced sepsis four months after the initial presentation.

Conclusion：This case highlights the importance of considering leukemic relapse as a differential diagnosis of orbital tumors in patients with a history of leukemia.