祝田 勇輝¹, 成田 啓一¹, 金田 智¹, 岩澤 沙友里¹, 井手 広樹², 廣瀬 茂道³, 塩見 英佑¹

Yuki IWAITA¹, Keiichi NARITA¹, Satoshi KANEDA¹, Sayuri IWASAWA¹, Hiroki IDE², Shigemichi HIROSE³, Eisuke SHIOMI¹

¹東京都済生会中央病院放射線科, ²東京都済生会中央病院泌尿器科, ³東京都済生会中央病院病理診断科

¹Department of Radiology, Tokyo Saiseikai Central Hospital, ²Department of Urology, Tokyo Saiseikai Central Hospital, ³Department of Diagnostic Pathology, Tokyo Saiseikai Central Hospital

キーワード : paratesticular fibrous pseudotumor, tunica vaginalis, ultrasonography, magnetic resonance imaging, testis-sparing surgery

傍精巣線維性偽腫瘍（paratesticular fibrous pseudotumor）は陰嚢内に発生する稀な良性腫瘍である．術前の悪性腫瘍との鑑別はしばしば難しいものの，腫瘍と精巣の剥離が可能であれば，特に若年者では精巣温存が望ましい．今回我々は，精巣温存が可能であった傍精巣線維性偽腫瘍を経験したため報告する．症例は30歳代男性．左陰嚢腫大を認め，超音波で陰嚢内充実性腫瘤を認めたため当院紹介受診した．当院で施行した超音波検査Bモードでは，肥厚した精巣鞘膜と連続性を有する多結節状の低エコー腫瘤を認め，カラードプラ法では腫瘤に軽度の血流シグナルを認めた．MRI検査ではT1強調像，T2強調像, 拡散強調像のいずれも低信号を示し，中等度の造影増強効果を認めた．悪性腫瘍も鑑別と考え手術を施行し，精巣との癒着は目立たなかったため，精巣は温存し陰嚢内腫瘤切除術を行った．病理組織学的には，腫瘤は高度に硝子化した線維組織を本体とし，炎症細胞の集簇が散在しており，精巣鞘膜由来の線維性偽腫瘍との最終診断に至った．精巣鞘膜と連続する多結節状の腫瘤で，超音波検査で低エコー，MRI検査のT1強調像，T2強調像，拡散強調像で低信号を示す腫瘤をみた場合，傍精巣線維性偽腫瘍が鑑別の上位に挙げられ，術中に精巣との剥離が可能であれば精巣温存ができることもある．

Paratesticular fibrous pseudotumor is a rare benign intrascrotal lesion. Although it may be difficult to preoperatively distinguish from malignancy, testis-sparing surgery is preferable if the tumor and testis can be dissected, especially in younger patients. We report a case of a paratesticular fibrous pseudotumor in which orchiectomy could be avoided. A man in his thirties presented with left scrotal swelling. An ultrasound examination revealed hypoechoic multinodular solid lesions attached to the thickened tunica vaginalis. Color Doppler showed mild vascularity in the nodules. Magnetic resonance imaging (MRI) revealed low signal intensity on T1-, T2-, and diffusion-weighted images with moderate contrast enhancement. Since the adhesion between the mass and the testis was not noticeable on surgical exploration, testis-sparing surgery was performed. Histopathologically, there was densely hyalinized fibrous tissue with scattered aggregates of inflammatory cells. The final histopathological diagnosis was a fibrous pseudotumor of the tunica vaginalis. Fibrous pseudotumor should be considered when a multinodular mass attached to the tunica vaginalis is hypoechoic on ultrasonography and shows low signal intensity on MRI T1-, T2-, and diffusion-weighted images. If the testis and the mass can be dissected intraoperatively, testicular sparing may be possible.