Stomach Mass
A stomach mass is any abnormal growth arising from or within the wall of the stomach. The term covers a wide range, from entirely benign polyps and fatty tumors to gastrointestinal stromal tumors, neuroendocrine tumors, lymphoma, and gastric adenocarcinoma. Many are found incidentally—during an endoscopy performed for reflux or indigestion, or on a CT scan ordered for something unrelated—and cause no symptoms at all. Others present with discomfort, difficulty eating, or bleeding. Because the layer of the stomach wall a mass arises from largely determines what it is, evaluation combines endoscopy to see the mucosal surface directly, endoscopic ultrasound to assess depth, and CT to define the mass and check for spread.
What is it?
The stomach wall is built in layers: an inner mucosa that produces acid and enzymes and is in contact with food, a submucosa beneath it carrying blood vessels and nerves, a thick muscular layer that churns and propels contents, and an outer serosal covering. A mass can arise from any of these layers, and identifying the layer of origin is the single most informative step in determining what a mass is.
Stomach mass is a descriptive finding rather than a diagnosis. It is what an endoscopist sees, a radiologist reports, or a patient learns from a scan result before the cause is established. The evaluation is one of characterization, and the reassuring background fact is that benign lesions substantially outnumber malignant ones among masses discovered incidentally.
Masses arising from the mucosa—the inner lining—are visible directly at endoscopy and can be biopsied straightforwardly.
Gastric polyps are the most common. Fundic gland polyps are now the most frequently encountered type in Western populations, appearing as small, smooth, often multiple lesions in the upper stomach. They are strongly associated with long-term proton pump inhibitor use, which is the principal reason their frequency has risen. Sporadic fundic gland polyps carry essentially no malignant potential and generally require no treatment, though numerous fundic gland polyps in a young patient can indicate familial adenomatous polyposis and warrant further evaluation.
Hyperplastic polyps arise in stomachs affected by chronic inflammation, classically from Helicobacter pylori infection or autoimmune gastritis. They can bleed and cause iron deficiency. Larger ones carry a small risk of harboring dysplasia and are removed; eradicating H. pylori frequently causes them to regress.
Gastric adenomas are true neoplastic polyps with genuine malignant potential and are removed endoscopically, with subsequent surveillance.
Gastric adenocarcinoma is the most common stomach cancer and arises from the mucosa. It is broadly divided into intestinal type, which typically develops through a sequence of chronic H. pylori gastritis, atrophy, intestinal metaplasia, and dysplasia, and diffuse type, which infiltrates the wall without forming a discrete mass and includes signet ring cell carcinoma. Diffuse type produces linitis plastica when it thickens and stiffens the entire stomach wall, an appearance sometimes described as a leather bottle stomach, and it can be difficult to detect on both endoscopy and imaging because it spreads within the wall rather than projecting into the lumen. Established risk factors include H. pylori infection, which is the dominant modifiable cause worldwide; smoking; diets high in salt and preserved or smoked foods; pernicious anemia and autoimmune atrophic gastritis; prior gastric surgery; obesity for tumors near the gastroesophageal junction; and hereditary syndromes, most notably hereditary diffuse gastric cancer associated with CDH1 mutations, which carries a high lifetime risk and has significant implications for the patient’s family.
Masses arising beneath the mucosa are covered by normal-appearing lining and are described as subepithelial lesions. This is the group where endoscopic ultrasound is most valuable, since a normal-looking surface tells the endoscopist very little and standard biopsies frequently return only normal mucosa.
Gastrointestinal stromal tumors, or GISTs, are the most common of these. They arise from the interstitial cells of Cajal, the pacemaker cells that coordinate gut motility, and are driven in most cases by mutations in the KIT or PDGFRA genes. The stomach is the most common site. Their behavior spans a spectrum from essentially benign to frankly malignant, and risk is estimated using tumor size, location, and mitotic rate rather than a simple benign-or-malignant classification. Small gastric GISTs are frequently found incidentally, and many never cause problems. Larger ones classically present with bleeding, because they can ulcerate through the overlying mucosa, and they may show central necrosis or cavitation on imaging.
Leiomyomas are benign smooth muscle tumors, more common in the esophagus but occurring in the stomach. Lipomas are benign fatty tumors with a characteristic appearance on CT that usually allows confident diagnosis without biopsy. Schwannomas arise from nerve sheath tissue and are typically benign. Ectopic pancreatic tissue—a small deposit of pancreatic tissue in the stomach wall, often with a central dimple—is a benign developmental finding.
Gastric neuroendocrine tumors, historically called carcinoids, are classified into distinct types with quite different implications. Type 1 arises in the setting of autoimmune atrophic gastritis, is usually small, multiple, and indolent, and is often managed with surveillance or endoscopic removal. Type 2 is associated with Zollinger-Ellison syndrome and multiple endocrine neoplasia type 1. Type 3 occurs sporadically without a background condition, behaves more aggressively, and is treated more like a conventional cancer. Distinguishing them is essential to appropriate management.
Gastric lymphoma most often takes the form of MALT lymphoma, arising from lymphoid tissue that develops in the stomach in response to chronic H. pylori infection. It is notable as one of the few cancers where treating an infection can be the primary treatment—a substantial proportion regress completely with H. pylori eradication alone. Diffuse large B-cell lymphoma of the stomach also occurs and is treated with systemic therapy.
Metastases to the stomach are uncommon but occur, particularly from melanoma, breast cancer—especially lobular type—and lung cancer.
A number of findings can mimic a true mass, which is worth knowing because they account for a share of masses reported on imaging. An incompletely distended stomach can produce apparent wall thickening on CT that disappears when the stomach is properly filled. Food residue, a large gastric fold, an adjacent organ such as the pancreas or spleen, and extrinsic compression can all be misinterpreted. This is one reason a CT finding of a possible gastric mass is generally confirmed with endoscopy rather than acted on directly.
Symptoms are frequently absent, particularly for small masses and early cancers, and this is a central reason gastric cancer is often diagnosed late in countries without screening programs.
When symptoms occur they are nonspecific and overlap substantially with ordinary indigestion: upper abdominal discomfort, persistent dyspepsia, early satiety, bloating, nausea, and reduced appetite. Because these symptoms are common and usually benign, guidelines direct endoscopy toward patients with alarm features or those over a certain age with new persistent symptoms.
More specific presentations include bleeding, which may be occult, producing iron deficiency anemia with fatigue and breathlessness, or overt, producing vomited blood or black tarry stools. Bleeding is a characteristic presentation of GISTs. Obstruction of the stomach outlet causes vomiting of undigested food and marked early satiety. Difficulty swallowing suggests involvement near the junction with the esophagus. Unintentional weight loss, a palpable upper abdominal mass, and a hard node above the left collarbone are features of advanced disease.
Evaluation follows a fairly standard sequence.
Upper endoscopy is the central test. It allows direct inspection of the entire gastric lining, characterization of the mass, and biopsy. Multiple biopsies are taken from suspicious lesions, since a single superficial sample can miss cancer, particularly in diffuse-type disease where the mucosal surface may look deceptively normal. Endoscopy also assesses for H. pylori and background changes such as atrophy and intestinal metaplasia.
Endoscopic ultrasound places an ultrasound probe within the stomach, providing a detailed cross-section of the wall layers. It determines which layer a subepithelial lesion arises from—the key to narrowing the diagnosis—measures size accurately, identifies features associated with higher risk, assesses regional lymph nodes, and allows fine needle biopsy under direct guidance. For subepithelial masses it is the single most informative test.
CT of the abdomen and pelvis with intravenous contrast defines the mass, its extension beyond the stomach wall, its relationship to adjacent organs, and the presence of enlarged lymph nodes, liver metastases, ascites, or peritoneal deposits. Adequate gastric distension, usually with water or an oral agent, is important for reliable assessment, and CT is central to staging once a cancer is diagnosed.
PET-CT is used selectively for staging. An important limitation is that signet ring cell, mucinous, and some diffuse-type gastric cancers are frequently not FDG-avid, so a negative PET does not exclude disease in these subtypes.
Diagnostic laparoscopy is used before major surgery for gastric cancer in many centers, because small peritoneal deposits that CT cannot detect are common and change the treatment plan substantially.
Blood tests support the assessment: complete blood count and iron studies for anemia, liver and kidney function, nutritional markers, and H. pylori testing. Tumor markers such as CEA and CA 19-9 are neither sensitive nor specific enough for diagnosis and are used mainly for monitoring.
Important to Know
Because stomach mass is a finding rather than a diagnosis, the guiding principle is establishing what the lesion is before deciding what to do about it. Many masses require nothing more than reassurance or a simple endoscopic removal, while others require staging and multidisciplinary treatment. Care is typically coordinated by gastroenterologists, with surgical and medical oncology involved when a malignancy is confirmed.
Gastric polyps are managed according to type. Small sporadic fundic gland polyps generally require no treatment or follow-up, and a report describing them is usually not a cause for concern. Numerous fundic gland polyps in a younger patient prompt evaluation for familial adenomatous polyposis. Hyperplastic polyps larger than about a centimeter are typically removed, and H. pylori is eradicated where present, which often causes remaining polyps to regress. Adenomas are removed completely because of their malignant potential, with surveillance endoscopy thereafter. When polyps arise on a background of atrophic gastritis or intestinal metaplasia, the background mucosa carries its own risk and may warrant periodic surveillance independent of the polyps themselves.
Helicobacter pylori eradication deserves emphasis as one of the clearest preventive interventions in this area. Treating the infection reduces the risk of gastric cancer, causes many hyperplastic polyps to regress, and can by itself cure a substantial proportion of gastric MALT lymphomas. Testing and treating is appropriate whenever the infection is identified in a patient with gastric pathology.
Gastrointestinal stromal tumors are managed by risk rather than by a simple benign-or-malignant designation. Small gastric GISTs without high-risk features on endoscopic ultrasound may be monitored with periodic surveillance, an approach supported by their frequently indolent behavior. Larger tumors, those with concerning features, and symptomatic tumors are resected, with the goal of complete removal with an intact capsule rather than wide margins, since these tumors rarely spread to lymph nodes and can seed if ruptured. Mutational testing guides the use of imatinib and related targeted agents, which may be given before surgery to shrink a large tumor or afterward to reduce recurrence risk in higher-risk disease. Response to these agents depends on the specific mutation, which is why molecular testing is standard.
Gastric MALT lymphoma is treated first with H. pylori eradication in H. pylori-positive disease, with a substantial proportion achieving complete remission, though response can take months and requires patient follow-up endoscopy rather than premature escalation. Cases that do not respond, that lack H. pylori, or that carry specific chromosomal changes associated with resistance are treated with radiotherapy, immunotherapy, or chemotherapy.
Gastric adenocarcinoma treatment depends on stage. Very early cancers confined to the mucosa and meeting specific criteria can be removed endoscopically through endoscopic submucosal dissection, avoiding major surgery entirely—an approach used extensively in countries with screening programs where more cancers are caught early. More advanced but localized disease is treated with gastrectomy and lymph node dissection, usually combined with chemotherapy given before and after surgery. Advanced disease is treated with systemic therapy, increasingly guided by molecular testing for HER2, PD-L1, and mismatch repair status, which determine eligibility for targeted agents and immunotherapy.
Gastric neuroendocrine tumors are managed by type. Type 1 tumors associated with atrophic gastritis are often small and indolent and are managed with endoscopic removal and surveillance. Type 3 sporadic tumors behave more aggressively and are treated with formal surgical resection. Correct typing is therefore essential and depends on assessing the background stomach and gastrin levels rather than the tumor alone.
Surveillance after treatment varies by diagnosis, from no follow-up for a benign fundic gland polyp, to periodic endoscopy for adenomas and atrophic gastritis, to structured oncologic follow-up after cancer treatment.
A specific point deserves mention for families. Hereditary diffuse gastric cancer, associated with CDH1 mutations, carries a high lifetime risk of diffuse gastric cancer that endoscopic surveillance detects poorly, since the disease spreads within the wall without forming a visible lesion. Risk-reducing total gastrectomy is discussed with mutation carriers, and genetic counseling for relatives is important. Diffuse gastric cancer in a young patient, or a family history of gastric or lobular breast cancer, should prompt consideration of genetic assessment.
Nutritional support is relevant across many of these conditions. Reduced intake from early satiety, obstruction, or after gastric surgery affects weight, strength, and treatment tolerance, and dietitian involvement is valuable. Patients who have had part or all of the stomach removed require long-term monitoring for vitamin B12, iron, calcium, and vitamin D deficiency, along with dietary adaptation to smaller, more frequent meals.
Care is typically coordinated by gastroenterology, with surgery, medical oncology, pathology, radiology, genetics, and dietetics involved as needed. Imaging, endoscopic, laboratory, and clinical findings are interpreted alongside the patient’s symptoms, examination, family history, and broader clinical context rather than in isolation.
Patient education plays an important role. Understanding that most incidentally found stomach masses are benign, why endoscopy and endoscopic ultrasound are often needed rather than imaging alone, why a normal-looking stomach lining does not exclude a lesion beneath it, why treating an infection can be the treatment for a lymphoma, why some tumors are watched rather than removed, and which symptoms warrant prompt evaluation all contribute to appropriate care.
Red flag symptoms include difficulty or pain on swallowing; persistent vomiting, particularly of undigested food; vomiting blood or material resembling coffee grounds; black tarry stools; unintentional weight loss; persistent upper abdominal pain; new or worsening early satiety; fatigue and breathlessness suggesting anemia; a palpable upper abdominal mass; jaundice; and new persistent indigestion beginning in a patient over the age of about 55 or accompanied by any of the above. These warrant prompt medical evaluation and generally an upper endoscopy, as they may indicate bleeding, obstruction, or malignancy.