What could be causing a lump in the upper left abdomen of an adult with a possible history of gastrointestinal issues?

Upper Left Abdominal Lump: Diagnostic Approach and Management

The most critical first step is to obtain cross-sectional imaging with CT abdomen and pelvis with IV contrast to characterize the mass, as gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in this location and require urgent surgical evaluation. 1

Immediate Diagnostic Workup

Clinical Assessment

• Assess for alarm features including weight loss, early satiety, abdominal pain, gastrointestinal bleeding (hematemesis, melena), fever, and palpable mass characteristics (size, mobility, consistency, tenderness). 1
• Exclude cardiac ischemia first in patients with upper abdominal pain, especially with obesity or cardiovascular risk factors, as myocardial infarction can present atypically with 10-20% mortality if missed. 2
• Document symptom duration and progression, as GISTs commonly present with gradually enlarging masses over months, often with dull aching pain and early satiety. 3, 4

Imaging Strategy

• CT abdomen and pelvis with IV contrast is the primary imaging modality for characterizing upper abdominal masses, assessing relationship to surrounding structures, and detecting metastases. 1
• Use neutral oral contrast (water or dilute barium) to optimize gastric wall visualization and distinguish intraluminal from extraluminal pathology. 1
• CT has 53-85% sensitivity for gastrointestinal pathology but is essential for surgical planning and detecting complications like perforation or bleeding. 1

Differential Diagnosis by Location

Most Likely: Gastric GIST

• GISTs are the most common mesenchymal tumors of the stomach, presenting as palpable masses in the upper left abdomen, often arising from the gastric fundus or anterior wall. 1, 3, 4
• Large GISTs (>10 cm) frequently present with palpable masses, early satiety, and dull abdominal pain due to mass effect. 3, 5, 4
• Preoperative biopsy is essential via EUS-guided fine needle aspiration or CT-guided core biopsy to confirm diagnosis and perform mutational analysis (CD117, DOG1 immunostaining) before surgery, especially for large tumors requiring complex resection. 1

Alternative Diagnoses to Consider

• Gastric cancer: More common in patients >55 years with alarm symptoms (weight loss, anemia, anorexia), family history, or H. pylori infection; requires endoscopy with biopsy. 1
• Splenic pathology: Splenomegaly from hematologic disorders or splenic masses can present as left upper quadrant lumps. 1
• Pancreatic tail masses: Pancreatic tumors or pseudocysts may present in the left upper abdomen; MRCP can help characterize. 1
• Renal masses: Giant hydronephrosis or renal tumors can mimic intra-abdominal masses; ultrasound and CT with contrast distinguish these. 6

Endoscopic Evaluation

When to Perform Endoscopy

• Upper endoscopy (EGD) with biopsy is indicated if CT suggests gastric wall origin, to visualize mucosal involvement and obtain tissue diagnosis. 1
• EUS is superior to standard endoscopy for characterizing submucosal masses, determining layer of origin (muscularis propria vs. submucosa), and guiding biopsy. 1
• Flexible sigmoidoscopy or colonoscopy is NOT indicated unless patient has concurrent lower GI symptoms (diarrhea, hematochezia), as left upper abdominal masses rarely originate from the colon. 1

Tissue Diagnosis Requirements

• Preoperative histologic diagnosis is mandatory for large or complex tumors (>10 cm, requiring multi-visceral resection) to guide neoadjuvant therapy decisions. 1
• Mutational analysis (KIT, PDGFRA) is essential if GIST is confirmed, as imatinib-resistant mutations alter treatment strategy. 1
• CD117 and DOG1 immunostaining confirm GIST diagnosis, distinguishing it from leiomyosarcoma (positive for smooth muscle actin/desmin, negative for CD117). 1, 3

Management Algorithm

Surgical Approach

• Complete surgical resection is the primary treatment for localized GISTs, performed by surgeons experienced in sarcoma management at specialist centers. 1
• En bloc resection with negative margins (R0 resection) is the goal, avoiding tumor rupture which worsens prognosis. 1
• Laparotomy is preferred for large tumors (>10 cm) due to complex vascular relationships and risk of rupture with laparoscopic manipulation. 4

Adjuvant Therapy

• Postoperative imatinib (400 mg daily) is recommended for high-risk GISTs (>5 cm, high mitotic rate, tumor rupture) to reduce recurrence risk. 1, 3, 7
• Treatment duration is typically 3 years for high-risk tumors based on current evidence. 1
• Neoadjuvant imatinib may be considered for large tumors requiring extensive resection (total gastrectomy, multi-visceral resection) to downstage and improve resectability. 1

Critical Pitfalls to Avoid

• Never delay imaging for empiric medical therapy in patients with palpable abdominal masses, as this delays diagnosis of potentially curable malignancies. 1
• Do not assume benign etiology based on age alone—GISTs occur across all age groups, including children and young adults. 7
• Avoid percutaneous biopsy of cystic masses without imaging guidance, as this risks peritoneal seeding; target solid components when possible. 1
• Do not perform diagnostic laparotomy without preoperative tissue diagnosis for large complex masses, as neoadjuvant therapy may be indicated. 1
• Ensure CD117 immunostaining is performed on all suspected GISTs, as this distinguishes them from morphologically similar tumors requiring different management. 1, 3