Adenoma-like adenocarcinoma: a subtype of colorectal carcinoma with good prognosis, deceptive appearance on biopsy and frequent KRAS mutation.
OBJECTIVE
A subset of colorectal carcinomas (CRCs) architecturally and cytologically resembles adenomatous change, making them difficult to diagnose on biopsy. This subset has not been well characterized to date.


RESULTS
For 35 carcinomas with adenomatous-like areas (cytological and surface architectural appearance that would be insufficient to warrant a diagnosis of adenocarcinoma if evaluated on biopsy), we recorded staging information, molecular data, clinical outcome, whether precursor adenoma was present and whether previous biopsy had been diagnosed as malignant. Despite advanced T-category in 23 (66%) tumours, only seven (20%) had nodal metastases, and only five patients (15%) developed distant metastases. Fifteen cases (43%) had been diagnosed as adenoma on biopsy. Twenty-one resections (60%) showed no residual associated adenoma, including nine called adenoma on biopsy. Median follow-up was 44 months. Four patients (12%) died of disease; 22 were alive at last follow-up. KRAS mutation was seen in 14 of 24 (58%) and four of 17 (24%) were microsatellite-unstable. Patients had significantly improved survival compared to a cohort of patients with conventional well-differentiated CRC after controlling for age and stage (P = 0.011).


CONCLUSIONS
Adenoma-like adenocarcinoma is an uncommon variant of CRC with a low rate of metastasis and good prognosis. Biopsy diagnosis of this lesion may be challenging.
Department of Pathology and Laboratory Medicine, University of Rochester Medical Center, Rochester, NY, USA.
Raul S
http://orcid.org/0000-0001-5526-4220
RS
Gonzalez
Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA.
Justin M M
JM
Cates
Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA.
Mary Kay
MK
Washington
Department of Surgery, Vanderbilt University Medical Center, Nashville, TN, USA.|Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN, USA.|Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN, USA.
Robert Daniel
RD
Beauchamp
Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN, USA.|Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA.
Robert J
RJ
Coffey
Department of Pathology, Microbiology and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA.
Chanjuan
C
Shi
D000230:Adenocarcinoma / Q000145:classification / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D000236:Adenoma / Q000473:pathology*; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D015179:Colorectal Neoplasms / Q000145:classification / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D009154:Mutation; D011379:Prognosis; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*
C117307:KRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)
adenoma-like adenocarcinoma; colorectal adenocarcinoma; gene mutation; microsatellite instability; prognosis