Pathology Lecture Apr 2026

"Margaret was a retired librarian. Non-smoker. Walked three miles a day. Six months ago, she noticed she felt full after eating only a few bites. She thought it was age. Three months ago, she noticed her stool was darker. She thought it was iron pills. Two weeks ago, she felt a lump in her right lower quadrant. She thought it was a muscle.

She turns off the projector. The room is silent.

The autopsy—which I performed—showed a 4 cm liver metastasis that had replaced 60% of her liver parenchyma. The primary colon tumor had perforated silently, walled off by the omentum. And here’s what matters: we found two tiny metastases in her lungs, each 2 mm. Too small to see on CT. That’s why she didn’t respond fully to chemo—the disease was always one step ahead." pathology lecture

The pathologist (me) signed it out: 'Moderately differentiated adenocarcinoma of the colon, with lymphovascular invasion, metastatic to liver.'

She pauses.

Stage IV. Incurable."

She begins to feel that vague fullness. Not pain. Just wrongness. The tumor is stiff, non-compliant. Food passing through feels like forcing a grape through a garden hose." The slide shows a cartoon of a tumor cell breaking off, entering a bloodstream, and landing on a liver. "Margaret was a retired librarian

And the macrophages believed it.

"Margaret chose palliative chemo. She had eight good months. Then the liver metastases grew. She developed ascites—fluid in the belly from portal hypertension. Then jaundice—the liver couldn’t clear bilirubin. Then confusion—ammonia from the gut bypassing the failed liver. Six months ago, she noticed she felt full

"At this point, Margaret felt nothing. The polyp was a tiny mushroom growing in the dark. But on a colonoscopy, it would have looked like a raised red bump. If we had caught it then, we would have snip-snipped it out. Case closed. We didn't." Part 2: The Invasion (Breaking the Basement Membrane) An animation shows cells piling up, pushing through a thin blue line (the basement membrane).