Resection of rectal cancer resembling submucosal tumor that was preoperatively diagnosed with endoscopic ultrasound-guided biopsy
© The Author(s). 2017
Received: 3 April 2017
Accepted: 11 July 2017
Published: 26 July 2017
Colorectal cancer (CRC) resembling submucosal tumor (SMT; CRC/SMT) is very rare. Because its biopsy is challenging, accurate preoperative diagnosis is also very rare.
A 55-year-old woman with a high serum carcinoembryonic antigen level underwent a computed tomography colonoscopy, which showed extrinsic rectum compression. A coronal magnetic resonance image showed a 4-cm low-intensity tumor between her rectum and sacrum. Endoscopic ultrasound (EUS) showed a 30-mm low-echoic lesion originating from the rectum. Pathological examination of specimen obtained with EUS-guided fine-needle aspiration biopsy (EUS-FNAB) revealed adenocarcinoma. Immunohistochemical staining showed the tumor to be positive for both CK20 and CDX2 and negative for CK7, indicating that it was a rectal cancer. We performed a laparoscopy-assisted low-anterior resection with dissection of the regional lymph nodes after eight chemotherapy cycles. Macroscopically, tumor was completely covered by normal rectal mucosa, but showed a 2-mm bulge on the mucosa. Histological examination revealed a moderately differentiated adenocarcinoma, mainly located at the subserosal layer and severely invaded to lymphatic and blood vessels. The mucosal layer was not exposed to the cancer components, and her postoperative course was uneventful.
EUS-FNAB was useful in preoperative accurate diagnosis of this very rare tumor. We also review the literature and discuss CRC/SMT.
Submucosal tumor (SMT) usually arises from tissue in the wall of digestive tract, and its surface is therefore covered with normal mucosa in most cases. In contrast, gastrointestinal (GI) carcinomas arise from the epithelium, and most of their mucosal surfaces typically consist of cancerous tissue. SMT-like growth is an unusual presentation for GI carcinomas, especially in colorectal cancer (CRC). We herein report a rare case of rectal cancer resembling SMT (CRC/SMT) in which endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNAB) was useful in accurate preoperative diagnosis. We also review the literature and discuss CRC/SMT.
Carcinomas of the digestive tract arise from the mucosal epithelium; most of their mucosal surfaces consist of cancerous tissues. Although cancer cells then infiltrate both horizontally and vertically, the dominant direction depends on the nature of the cancer cells. Some intestinal cancers dominantly infiltrate in a vertical direction without massive invasion along the horizontal plane. As a result, the internal intestinal surfaces over these tumors are mostly covered with normal mucosa, and therefore manifest as SMTs. This type of tumor is sometimes called a carcinoma resembling an SMT; and although it is extremely rare, has been reported in the esophagus , stomach , and colon and rectum [3, 4]. A report that reviewed 70 reported cases of CRC/SMT found it to be characterized by small tumor size, high rates of poorly differentiated adenocarcinoma or mucinous adenocarcinoma, and invasiveness (including high rates of lymph node metastasis and lymphatic vessel invasion) .
Reported cases of colorectal cancer resembling SMT in which tumor was completely covered with normal colorectal mucosa
Depth of invasionb
Histologic diagnosis of biopsy specimen
Histologic diagnosis of resected specimenc
Lymph node metastasis
Secondly, our case clearly showed that EUS-FNAB is useful for accurate preoperative diagnosis of CRC/SMT. EUS-FNAB was recently shown to be useful in accurate preoperative diagnosis of gastrointestinal stromal tumor (GIST)  and pancreatic cancer . Previous reports have shown the difficulty of preoperative CRC/SMT diagnosis, because of the difficulty of obtaining biopsy specimens. Therefore, EUS-FNAB should be considered to make accurate preoperative SMT diagnoses in colon and rectum. To our knowledge, our case is the first to use EUS-FNAB for an accurate preoperative diagnosis of CRC/SMT.
We should keep in mind that colorectal cancer can present with SMT-like growth. Furthermore, EUS-FNAB is useful for preoperative accurate diagnosis of this rare colorectal cancer.
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