A surgical pathologist examines a resected colonic polyp. Histology shows full-thickness dysplasia, budding of glands, and single-cell infiltration into the muscularis mucosae but NOT into the submucosa. This is classified as:

• A Intramucosal carcinoma (pTis) ✓
• B pT1 adenocarcinoma
• C High-grade adenoma
• D pT2 adenocarcinoma

Explanation

Intramucosal carcinoma (pTis) is diagnosed when neoplastic cells invade into the lamina propria or muscularis mucosae but do NOT penetrate through the muscularis mucosae into the submucosa. In the colon, because the muscularis mucosae separates mucosa from the rich submucosal lymphatics, intramucosal carcinoma carries negligible risk of metastasis and is managed by complete local excision. pT1 requires invasion into the submucosa; pT2 requires invasion of the muscularis propria.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.