The gross specimen of a resected segment of the colon shown above demonstrates a large, irregular, fungating mass protruding into the lumen. What is the most likely diagnosis?

Explanation

## Image Findings * Resected segment of **colon** with preserved serosa and mesentery. * Presence of a **large, irregular, fungating (exophytic) mass** protruding significantly into the colonic lumen. * The mass has a **friable and reddish-brown appearance**, suggesting necrosis and hemorrhage. * The adjacent colonic mucosa appears relatively normal, though some congestion is noted. * The overall appearance is that of a **proliferative, invasive lesion**. ## Diagnosis **Key Point:** The gross appearance of a large, irregular, fungating, exophytic mass within the colonic lumen is pathognomonic for **colon carcinoma**. The image clearly demonstrates a **resected segment of the colon** containing a prominent, **fungating (polypoid/exophytic) mass**. This mass is **irregular** in shape, appears **friable**, and projects significantly into the lumen. This gross morphology, characterized by an invasive, proliferative lesion, is highly characteristic of an **adenocarcinoma** of the colon, which is the most common type of colorectal cancer. The exophytic growth pattern indicates that the tumor is growing outwards from the mucosal surface into the lumen, a common presentation for advanced colorectal carcinomas. ## Differential Diagnosis | Feature | Colon Carcinoma | Ulcerative Colitis | Crohn's Disease | Diverticulitis | | :------------------ | :-------------------------------------------- | :-------------------------------------------------- | :-------------------------------------------------- | :------------------------------------------------- | | **Gross Appearance**| **Large, irregular, fungating/exophytic mass**; friable, often ulcerated. | Diffuse, continuous mucosal inflammation; **pseudopolyps** (inflammatory, not neoplastic mass); loss of haustra. | **Skip lesions**; cobblestoning; deep linear ulcers; strictures; fistulas; transmural inflammation. | Outpouchings (diverticula); inflammation/abscess around diverticula; not a primary intraluminal mass. | | **Nature of Mass** | **Neoplastic (malignant)** | Inflammatory (reactive hyperplasia) | Inflammatory (granulomatous) | Inflammatory (peridiverticular) | | **Mucosa** | Adjacent mucosa often normal or congested. | Erythematous, granular, friable, diffuse involvement. | Patchy inflammation, deep ulcers, cobblestoning. | Normal between diverticula, inflamed around them. | | **Wall Involvement**| Full thickness (invasive) | Mucosal and submucosal only | Transmural | Peridiverticular, can lead to perforation/abscess. | ## Clinical Relevance **Clinical Pearl:** Colorectal carcinoma often presents with non-specific symptoms such as a change in bowel habits (diarrhea or constipation), rectal bleeding (hematochezia or melena), iron deficiency anemia, unexplained weight loss, and abdominal pain. Early detection through screening (e.g., colonoscopy, fecal occult blood test) is crucial for improving prognosis. ## High-Yield for NEET PG **High-Yield:** The most common type of colorectal cancer is **adenocarcinoma**, accounting for over 95% of cases. **Key Point:** Risk factors include increasing age, inflammatory bowel disease (Ulcerative Colitis, Crohn's Disease), inherited syndromes like Familial Adenomatous Polyposis (FAP) and Hereditary Non-Polyposis Colorectal Cancer (HNPCC/Lynch Syndrome), and certain dietary factors. The rectosigmoid colon is the most common site. ## Common Traps **Warning:** Distinguishing a true neoplastic fungating mass from large inflammatory pseudopolyps seen in severe ulcerative colitis can be challenging on gross examination alone. However, pseudopolyps are typically multiple, smaller, and represent regenerative mucosa amidst ulceration, lacking the invasive, irregular, and often solitary nature of a carcinoma. ## Reference [cite:Robbins Basic Pathology, 10th Edition, Chapter 15: The Gastrointestinal Tract, page 639-640]