Gastric Cancer & GIST
- Gastric adenocarcinoma grows from the lining inward, so it thickens or ulcerates the stomach wall — watch for a stiff, non-distending segment that won't balloon out when you inflate the stomach.
- A GIST is a different beast entirely: it grows from the wall's muscle layer outward, so it tends to be a round, exophytic mass that bulges away from the lumen rather than narrowing it.
- The wall-layer of origin is the whole punchline: mucosa-up = carcinoma, deep-muscle = GIST.
- Stage the adenocarcinoma by following its spread — local wall, then nodes, then peritoneum and liver. CT is your workhorse for the metastatic survey.
- "Linitis plastica" is the dreaded diffuse form: the whole stomach turns into a rigid, shrunken leather pouch.
Two tumors share one organ on this page, and the kindest thing I can do is tell you up front that they have almost nothing in common except a zip code. One sneaks along the lining of the stomach like mold creeping across bread. The other shoves outward from the muscle wall like a knuckle pushing into a balloon from the outside. Get that one distinction straight and the imaging mostly explains itself.
Gastric adenocarcinoma: the lining gone wrong
The stomach wall is layered like a sandwich — mucosa on the inside, then submucosa, then muscle, then a thin outer coat. Adenocarcinoma starts at the innermost layer (the mucosa) and works its way down and along. That origin point is why it behaves the way it does on imaging: it thickens the wall and stiffens it.
The single most useful trick for the stomach is distension. A normal stomach, gently inflated with water or gas for a CT, balloons out smoothly and the wall thins like a stretched balloon. A segment infiltrated by tumor refuses to play along — it stays thick, irregular, and rigid while everything around it expands. That stubborn, non-distensible patch is your tumor.
The classic forms show up as either a polypoid mass poking into the lumen, an ulcerating lesion (a crater with heaped-up rims), or the diffuse infiltrating type. On an old-school barium study — which still teaches the anatomy beautifully — a malignant ulcer sits within the wall contour with rigid, clubbed folds radiating toward it, whereas a benign ulcer pokes out past the expected wall line.
Linitis plastica is the diffuse, scary version: tumor cells creep through the whole wall and trigger a desmoplastic reaction, shrinking the stomach into a thick-walled, rigid "leather bottle." On barium it's a narrowed, tube-like stomach that won't expand; on CT it's diffuse, marked wall thickening. It's named for leather for a reason — the organ becomes stiff and unyielding.
Staging: follow the spread
Once you've found it, your job shifts to how far has it gone, and CT of the chest, abdomen, and pelvis is the standard survey. You trace the tumor outward in the same order it travels:
| Where to look | What you're hunting for |
|---|---|
| Local wall | Depth of invasion; tumor breaching the outer wall into surrounding fat |
| Regional nodes | Enlarged or clustered perigastric and nearby nodes |
| Peritoneum | Nodular deposits, omental "caking," ascites — peritoneal spread |
| Distant organs | Liver lesions; spread to ovaries is a known pattern |
Small-volume peritoneal carcinomatosis is sneaky — a whisper of ascites or subtle omental nodularity is easy to scroll past, and it dramatically changes the plan. Always pair a gastric cancer read with a deliberate hunt through the peritoneum and a look at peritoneal carcinomatosis and the liver.
GIST: the outsider that pushes, not pulls
Now the plot twist. A gastrointestinal stromal tumor (GIST) arises from a pacemaker-type cell living in the deep muscle layer of the wall — nowhere near the lining. So instead of creeping along the mucosa, it balls up and grows outward, away from the lumen. The stomach is its most common home in the GI tract.
The imaging signature follows the biology: a round, well-defined mass that bulges exophytically off the stomach, often with most of its bulk hanging outside the organ. Smaller ones enhance smoothly; larger ones outgrow their blood supply and develop necrosis, ulceration, or even a cavity that communicates with the lumen.
Behavior is graded mostly by size and how fast the cells are dividing, not a tidy benign-versus-malignant line. A small, slow GIST can be nearly inert; a big one is treated as a real cancer. When GISTs spread, they favor the liver and the peritoneal surfaces — and notably they tend to spare the lymph nodes, the opposite of adenocarcinoma.
That nodal habit is a genuinely useful discriminator at the workstation: a bulky outward gastric mass with lots of enlarged perigastric nodes leans carcinoma; the same mass with clean nodes leans GIST.
Putting them side by side
If you remember one table from this page, make it this one.
| Feature | Adenocarcinoma | GIST |
|---|---|---|
| Layer of origin | Mucosa (inner lining) | Deep muscle (wall) |
| Growth pattern | Wall thickening, narrowing, ulceration | Round, exophytic, bulges outward |
| Lumen | Stiff, won't distend | Often preserved/displaced |
| Lymph nodes | Commonly involved | Usually spared |
| Spread | Nodes, peritoneum, liver | Liver, peritoneum (not nodes) |
Same organ, two completely different stories. The stomach is also the end of the swallowing tube, so a tumor here is a cousin in geography — though not in behavior — to esophageal cancer just upstream. When you open a gastric study, ask one question first — is this thickening the wall from the inside, or pushing it out from the deep muscle? — and the rest of the read falls into place.