上田 直幸^{1, 2}, 河岡 友和³, 浅田 佳奈^{1, 2}, 荒瀬 隆司^{1, 2}, 小林 剛⁴, 森 馨一⁵, 大段 秀樹⁴, 横崎 典哉², 有廣 光司⁵, 相方 浩³

Naoyuki UEDA^{1, 2}, Tomokazu KAWAOKA³, Kana ASADA^{1, 2}, Takashi ARASE^{1, 2}, Tsuyoshi KOBAYASHI⁴, Keiichi MORI⁵, Hideki OHDAN⁴, Michiya YOKOZAKI², Koji ARIHIRO⁵, Hiroshi AIKATA³

¹広島大学病院診療支援部, ²広島大学病院検査部, ³広島大学病院消化器代謝内科, ⁴広島大学病院消化器外科, ⁵広島大学病院病理診断科

¹Division of Clinical Support, Hiroshima University Hospital, ²Division of Laboratory Medicine, Hiroshima University Hospital, ³Department of Gastroenterology and Metabolism, Hiroshima University Hospital, ⁴Department of Gastroenterological Surgery, Hiroshima University Hospital, ⁵Department of Anatomical Pathology, Hiroshima University Hospital

キーワード : hepatocellular carcinoma, spontaneous complete necrosis, ultrasonography, contrast-enhanced ultrasonography

症例：70歳代の女性．血液検査異常にて当院紹介となった．既往歴はB型慢性肝炎，子宮，卵巣摘出後，高血圧．血液検査結果はAFP 2.5 ng/mlで正常範囲，PIVKA- II 216 mAU/mlと高値であったが，手術前日の検査で20 mAU/mlと低下していた．Child-Pugh分類はA（5点）．US：S2に14×12 mmの内部は比較的均一で境界明瞭，輪郭不整な低エコーSOLを認めた．明らかな被膜構造は認めなかった．CEUS：動脈優位相では辺縁の濃染を認めたが，実質はhypovascularであった．門脈優位相でも辺縁の濃染は持続していたが実質の濃染は認めなかった．後血管相では全体がdefectされていた．re-perfusion imagingでも同様に辺縁のみの濃染を認めた．CT：単純CTでは淡い低吸収域を認めた．動脈相で淡い早期濃染を認め，後期相では淡い低吸収域を認めた．EOB MRI：T1強調画像でS2に17 mmの肝細胞相で低信号を示すいびつな結節を認めた．血管造影下CT検査：S2に腫瘍濃染を認め，CTAPで17mmの低吸収域を認めた．その一部がCTHAで濃染を認めた．これらの結果より，中分化型肝細胞癌が疑われた．病理所見：壊死巣は線維性被膜を伴い，周囲には慢性炎症細胞や飛沫状組織球の浸潤を認めた．細胞のghostからは肝細胞癌が消失した像と見做された．結語：自然消失をきたしたと考えられた，肝細胞癌に対し造影超音波検査を施行し，特徴的な所見を認めた症例を経験した．

The patient was a woman in her 70s. She was referred to our hospital due to abnormal blood tests without any chief complaint. Her medical history included chronic hepatitis B, hysterectomy, post-oophorectomy, and hypertension. Her blood test revealed AFP 2.5 ng/ml, which was within the normal range, and PIVKA-II 216 mAU/ml, which was high, but it had decreased to 20 mAU/ml the day before surgery. There were no other particular findings. Ultrasonography showed a 14×12-mm hypoechoic space-occupying lesion with a relatively uniform, well-defined interior and irregular contours in segment 2 (S2). There was no obvious capsular structure. Because of its proximity to the heart, the blood flow signal on color Doppler was difficult to evaluate due to the beating heart. Plain CT showed a pale low-absorption area. As for EOB-MRI, T1-weighted images showed a 17-mm low-signal nodule in the hepatocellular phase at S2. On angiographic CT, tumor staining was seen in S2, and CTAP showed a 17-mm hypo-absorptive area. CTAP showed a 17-mm low-absorption area, part of which was stained by CTHA. Based on these results, intermediate differentiated hepatocellular carcinoma was suspected. Pathology revealed necrotic nests accompanied by a fibrous capsule and surrounded by an infiltrate of chronic inflammatory cells and droplet histiocytes. The cellular ghost was considered to be the image of a resolved hepatocellular carcinoma. We report a case of hepatocellular carcinoma that was thought to have resolved spontaneously. Contrast-enhanced ultrasonography revealed characteristic findings.