嶌森 直子¹, 岸野 智則^{1, 2}, 大西 宏明^{1, 2}, 多武保 光宏³, 寺戸 雄一⁴, 要 伸也⁵, 森 秀明⁶, 奴田原 紀久雄³, 東原 英二³, 渡邊 卓^{1, 2}

Naoko SHIMAMORI¹, Tomonori KISHINO^{1, 2}, Hiroaki OHNISHI^{1, 2}, Mitsuhiro TAMBO³, Yuichi TERADO⁴, Shinya KANAME⁵, Hideaki MORI⁶, Kikuo NUTAHARA³, Eiji HIGASHIHARA³, Takashi WATANABE^{1, 2}

¹杏林大学医学部付属病院臨床検査部, ²杏林大学医学部臨床検査医学, ³杏林大学医学部泌尿器科, ⁴杏林大学医学部病理学, ⁵杏林大学医学部第一内科, ⁶杏林大学医学部第三内科

¹Department of Clinical Laboratory, Kyorin University Hospital, ²Department of Laboratory Medicine, Kyorin University School of Medicine, ³Department of Urology, Kyorin University School of Medicine, ⁴Department of Pathology, Kyorin University School of Medicine, ⁵The First Department of Internal Medicine, Kyorin University School of Medicine, ⁶The Third Department of Internal Medicine, Kyorin University School of Medicine

キーワード : central echo complex, collecting (Bellini) duct carcinoma, diffuse, infiltrative growth, reniform shape preservation

集合管癌は腎癌全体の1％程度とまれであるが予後不良の腫瘍である．今回，右腎全体に腫瘍が浸潤したまれな集合管癌の1例を経験した．症例は60歳代男性．腹部超音波検査で右腎は全体的に腫大し，境界不明瞭で内部エコー不均一な腫瘍性病変が腎全体をびまん性に占拠しており，腎中心部エコー像は極端に縮小していた．しかし，その大きさにも関わらず腎の輪郭は比較的保たれていた．腫瘍のエコーレベルは対側の正常腎皮質と比較して等エコーであり，ドプラ法では血流信号の少ない乏血性腫瘍であった．我々が検索した限り，これまでに集合管癌の超音波画像の特徴を詳細にまとめた報告はない．1988年以降に国内で論文報告された63症例は主にCT画像や病理所見に基づく所見であるが，本症例を含めて集計したところ，29例中21例（72％）で腎の輪郭が保たれており，腫瘍血流は54例中52例（96％）が乏血性であった．本症例のように腎全体にびまん性に浸潤した例は少なく62例中7例（11％）であった．既報と本症例の超音波画像から，集合管癌は1）浸潤性発育の像を呈し，2）腫瘍が増大しても腎の輪郭は保たれ，3）腎中心部エコー像は変形・縮小し，4）腫瘍血流は乏しく，5）腫瘍のエコーレベルは低～高エコーと症例により様々であるという特徴を有すると考察した．このような超音波画像を腎臓に認めた場合，集合管癌を鑑別に入れ精査すべきであると思われる．

Collecting duct carcinoma, also known as Bellini duct carcinoma, is a renal tumor with poor prognosis that accounts for only 1% of all renal cancers. We encountered a rare case of collecting duct carcinoma infiltrating into the entire right kidney. The patient was a man in his 60s. Abdominal ultrasonography demonstrated an enlarged right kidney, which appeared to be occupied by a tumor with poorly defined margins. The central echo complex of the kidney appeared extremely narrow due to tumor growth. However, the reniform shape was relatively well-preserved despite the large size of the tumor. Tumor echogenicity was almost isoechoic when compared with the cortex of the normal left kidney. Doppler imaging demonstrated that the tumor was scarcely fed by the tumor vessels. To the best of our knowledge, no previous reports have precisely described sonographic features of collecting duct carcinoma. Although 63 reports have been published in Japan since 1988, most have described only the findings from computed tomography and/or pathological examination. According to this literature, preservation of a reniform shape was found in 72% (21/29) of cases, and tumor hypovascularity was evident in 96% (52/54). On the other hand, diffuse infiltrating growth into the entire kidney, as in the present case, was seen in only 11% (7/62). Considering these past reports and the findings in the present case, sonography of collecting duct carcinoma could show the following features: 1) infiltrative growth; 2) preservation of reniform shape irrespective of tumor size; 3) deformity or narrowing of the central echo complex due to tumor growth; 4) hypovascularity on Doppler imaging; and 5) non-characteristic echogenicity depending on individual cases. When such imaging findings are apparent on sonography, collecting duct carcinoma should be included among the differential diagnoses.