Usually significant architectural and/or cytologic atypia
Usually lacks significant architectural and/or cytologic atypia (high grade dysplasia may be misplaced occasionally but is typically accompanied by bland adenoma tissue)
Inflammatory or fibrotic stroma
Infiltrates through muscularis mucosae
Frequently demonstrable continuity with surface through a gap in the muscularis mucosae
Hemosiderin restricted to head of polyp
Hemosiderin common in stalk stroma
Glands not accompanied by lamina propria
Glands may be accompanied by lamina propria
Usually infiltrative, non-circumscribed
May occur throughout the colorectum
Virtually restricted to left colon
Collagen type IV weak, discontinuous
Collagen type IV strong, continuous around epithelial nests
E cadherin markedly decreased staining compared to overlying adenoma
E cadherin same intensity as overlying adenoma (high grade dysplasia may show decrease)
Grading / Staging
It is acceptable to grade simply as Low vs. High grade
Low grade ≥50% gland forming
>95% gland forming
50-95% gland forming
High grade <50% gland forming
5-49% gland forming
Signet ring (>50% of cells signet ring)
<5% gland forming
Use TNM staging
Lesions should be staged if the margins of resection are clear
Provisional stage may be given if margins are involved but should be clearly indicated as provisional
An adenoma containing only high grade dysplasia or intramucosal carcinoma is pTis
An adenoma containing carcinoma invasive into the stalk is pT1 (unless it invades into muscularis propria)
Risio M, Fiocca R. Malignant adenoma: diagnosis, staging, risk factors, lymph node involvement and problems of sampling. Tech Coloproctol. 2004 Dec;8 Suppl 2:s253-6.
Coverlizza S, Risio M, Ferrari A, Fenoglio-Preiser CM, Rossini FP. Colorectal adenomas containing invasive carcinoma. Pathologic assessment of lymph node metastatic potential. Cancer. 1989 Nov 1;64(9):1937-47.
Nivatvongs S. Surgical management of malignant colorectal polyps. Surg Clin North Am. 2002 Oct;82(5):959-66.
Hassan C, Zullo A, Risio M, Rossini FP, Morini S. Histologic risk factors and clinical outcome in colorectal malignant polyp: a pooled-data analysis. Dis Colon Rectum. 2005 Aug;48(8):1588-96.
Nusko G, Mansmann U, Partzsch U, Altendorf-Hofmann A, Groitl H, Wittekind C, Ell C, Hahn EG. Invasive carcinoma in colorectal adenomas: multivariate analysis of patient and adenoma characteristics. Endoscopy, 1997 Sep;29(7):626-31.
Lewin MR, Fenton H, Burkart AL, et al. Poorly differentiated colorectal carcinoma with invasion restricted to lamina propria (intramucosal carcinoma): a Follow-up Study of 15 cases. Am J Surg Pathol. 2007;31:1882-1886.
Shia J; Klimstra DS. Intramucosal Poorly Differentiated Colorectal Carcinoma: Can it be Managed Conservatively? Am J Surg Pathol. 2008 Oct;32(10):1586-1588.