Tsuchihashi Hiroshi, Ito Aya, Tsukada Hiroaki, Hasegawa Hitoshi, Naitoh Hiroyuki, Hanasawa Kazuyoshi, Okada Katsuji
Dept. of Surgery, Hino Memorial Hospital.
Gan To Kagaku Ryoho. 2011 Dec;38(13):2659-62.
A 56-year-old female patient was admitted, complaining of hematochezia. She was preoperatively diagnosed with poorly-differentiated carcinoma of anorectum with metastases in the lung and mesorectal lymph nodes, and underwent abdominoperineal resection of the rectum. The immunohistochemistry of the rectal tumor showed positive for vimentin and c-kit, and negative for AE1/AE3, S-100, a-SMA, LCA and CD34, which was compatible with gastrointestinal stromal tumor (GIST). Regardless of the administration of imatinib mesylate, multiple metastases in the brain, bone, adrenal glands and inguinal lymph node proceeded in a short term. An excisional biopsy of the inguinal lymph node was performed and immunohistochemistry of the specimen showed positive for S-100, melan-A, HMB45 and tyrosinase. Therefore, we concluded that amelanotic anorectal melanoma (AMM) metastasized to the lymph node, and rechecked the immuno histochemistry of the anorectal tumor. The anorectal tumor showed positive for melan-A, HMB45 and tyrosinase, but negative for S-100. As far as we know, there are few reports of AMM with S-100 negative and c-kit positive. In such cases, making a differential diagnosis between AMM and GIST of the anorectal region can be very confusing.
一名56岁女性患者因便血入院。她术前被诊断为低分化肛管直肠癌伴肺和直肠系膜淋巴结转移，接受了腹会阴联合直肠癌切除术。直肠肿瘤的免疫组化显示波形蛋白和c-kit阳性，AE1/AE3、S-100、α-SMA、LCA和CD34阴性，符合胃肠道间质瘤（GIST）。尽管使用了甲磺酸伊马替尼，短期内仍出现了脑、骨、肾上腺和腹股沟淋巴结的多发转移。对腹股沟淋巴结进行了切除活检，标本的免疫组化显示S-100、黑素A、HMB45和酪氨酸酶阳性。因此，我们得出结论，无色素性肛管黑色素瘤（AMM）转移至淋巴结，并重新检查了肛管肿瘤的免疫组化。肛管肿瘤黑素A、HMB45和酪氨酸酶阳性，但S-100阴性。据我们所知，S-100阴性且c-kit阳性的AMM报道很少。在这种情况下，鉴别诊断肛管区域的AMM和GIST可能非常困难。
