第22巻 2026年4月　第2号

■症例報告

CTにて自然史を確認できたIntracholecystic Papillary Neoplasmの1例
上田　圭馬¹, 岩田　琴美², 許田　典男³, 関根　鉄朗¹, ��木　瞳子¹, 汲田　伸一郎^1
1日本医科大学付属病院放射線科
²日本医科大学武蔵小杉病院放射線科
³日本医科大学武蔵小杉病院病理診断科

A Case of Intracholecystic Papillary Neoplasm with Natural History Documented by Computed Tomography
Keima Ueda¹, Kotomi Iwata², Norio Motoda³, Tetsuro Sekine¹, Toko Takagi¹ and Shin-ichiro Kumita^1
1)Department of Radiology, Nippon Medical School Hospital
²⁾Department of Radiology, Nippon Medical School Musashi Kosugi Hospital
³⁾Department of Pathology, Nippon Medical School Musashi Kosugi Hospital

Intracholecystic papillary neoplasm (ICPN) is a preinvasive neoplasm of the gallbladder that grows as an intraluminal papillary or polypoid lesion, but its imaging features have not been sufficiently characterized. The case presented here uniquely demonstrates the natural history of ICPN, documented by serial computed tomography over a two-year period during postoperative surveillance for renal cell carcinoma. A 63-year-old man was found to have a slowly enlarging hyperdense intraluminal gallbladder mass on unenhanced computed tomography (CT). Retrospective review demonstrated gradual growth over approximately two years. The lesion measured 45 mm in diameter and showed persistent enhancement from the early arterial phase through the equilibrium phase on dynamic contrast-enhanced CT. Magnetic resonance imaging revealed a papillary mass; T2-weighted imaging demonstrated mildly increased signal intensity within the soft-tissue component, and diffusion-weighted imaging showed diffuse mild hyperintensity throughout the tumor. Despite the large size, there were no imaging findings suggestive of advanced gallbladder carcinoma, such as irregular thickening of the gallbladder wall, extramural invasion, or metastatic disease. The patient underwent laparoscopic cholecystectomy. Histopathological examination demonstrated glandular proliferation with high-grade cytologic atypia and diffuse MUC6 positivity, consistent with gastric non-mucinous type ICPN with associated high-grade intraepithelial neoplasia. ICPN should be considered in the differential diagnosis of a papillary intraluminal gallbladder tumor that lacks clear evidence of invasion on imaging.

日医大医会誌 2026; 22(2), 167-171

Key words
intracholecystic papillary neoplasm, gallbladder, computed tomography

Correspondence to
Keima Ueda, Department of Radiology, Nippon Medical School Hospital, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan
E-mail：s15-014uk@nms.ac.jp

受付：2026年1月31日　受理：2026年3月6日