Published online Feb 14, 2017. doi: 10.3748/wjg.v23.i6.1106
Peer-review started: October 28, 2016
First decision: December 01, 2016
Revised: December 17, 2016
Accepted: January 4, 2017
Article in press: January 4, 2017
Published online: February 14, 2017
High-grade colonic neuroendocrine carcinomas (NECs) are uncommon but extremely aggressive. Their co-existence with tubular adenoma (TA) has rarely been reported. We present a 68-year-old man who was found on routine colonoscopy to have multiple colorectal TAs and an ulcerated lesion in the ascending colon. Microscopically, a poorly-differentiated invasive carcinoma juxtaposed with a TA was identified. Differential diagnosis included a poorly-differentiated adenocarcinoma, medullary carcinoma, high-grade NEC and lymphoma. The immunohistochemical profile showed positive staining for keratins, synaptophysin and chromogranin but negative for LCA, CDX2, CK7, CK20, TTF-1 and PSA, supporting the NEC diagnosis. Upon subsequent laparoscopic right hemicolectomy, the tumor was identified as a 3.0 cm umbilicated and ulcerated mass with an adjacent TA. Both TA and NEC showed positive staining for β-catenin indicating a shared colonic origin. The mitotic counts (77/10 high power fields) and a high proliferation rate (75% by Ki-67) corroborated a high-grade stratification. Mutational analysis indicated a wild-type BRAF and KRAS with mismatch repair proficiency. The AJCC (7th edition) pathologic stage is pT3, pN0, pMx. The patient received adjuvant chemotherapy with cisplatin/etoposides for three cycles and will be followed up for a year to detect recurrence. In conclusion, the co-existence of TA with high grade-NEC in our case allowed early identification and intervention of the otherwise asymptomatic but aggressive tumor. In addition, the finding of a high-grade NEC within a large TA in this case suggests a link between the two lesions and could represent a shared stem cell origin.
Core tip: This is a case report of a patient with a high-grade large cell neuroendocrine carcinoma in the ascending colon with an overlying tubular adenoma discovered during routine colonoscopic screening in absence of clinical symptoms. This is a unique case where the contiguity of the neuroendocrine carcinoma to the tubular adenoma allowed for the diagnosis of the otherwise asymptomatic high-grade carcinoma. Being aware of this association bears practical implication where it can be conducive to the early and correct diagnosis of invasive cancer. In addition, we review the literature citing pertinent cases.