S5182 Distinguishing Primary Gastric Leiomyosarcoma From a Gastrointestinal Stromal Tumour: A Case Report
Bibliographic record
Abstract
Introduction: Primary gastric leiomyosarcoma (LMS) comprises 1% of stomach tumors. Historically, gastric LMS were misdiagnosed as gastrointestinal stromal tumors (GIST), but immunohistochemistry allows differentiation. GISTs are positive for CD117, DOG1 and Platelet-derived growth factor receptor alpha (PDGFRA) mutation, whereas gastric LMS tumors are typically positive for smooth muscle actin (SMA) and desmin. This case highlights the importance of distinguishing a gastric LMS from a GIST in a patient with metastatic disease. Case Description/Methods: The patient is a 78-year-old woman diagnosed with a low-grade metastatic gastric LMS, initially presenting with abdominal pain. Imaging visualized a large heterogenous, solid-appearing possibly bilobed lesion suspected to be a GIST. Gastroscopy identified 2 submucosal lesions. Endoscopic guided ultrasound fine-needle aspiration demonstrated a smooth muscle neoplasm. It was desmin and SMA positive, while CD117 and DOG1 negative, consistent with LMS. The patient underwent laparoscopic resection. Pathology was consistent with low-grade LMS with negative margins. Furthermore, mutational analysis of CD117 and PDGRFA were negative, supporting the LMS diagnosis. Post-operative follow-up imaging demonstrated recurrence and the patient was referred for chemotherapy. The LMS was suspected to be responsive to chemotherapy due to its GIST-like behaviour. She received 3 cycles of doxorubicin but unfortunately developed significant side effects and therefore treatment was held. Repeat Computed tomography demonstrated disease progression and the decision was made to pursue palliative treatment. Discussion: Our case report highlights a rare disease entity, as LMS constitutes a small fraction of gastric malignancies. Potential risk factors include chromosomal mutations, radiation, immunosuppression, chemical exposure and infections such as Helicobacter pylorior Epstein-Barr virus. The patient had no prior radiation, chemical exposure, or immunosuppression. Gastric biopsies were negative for Helicobacter pyloriinfection. However, Epstein-Barr virus and chromosomal testing were not conducted. Standard therapy of gastric LMS involves complete laparoscopic or open resection. Endoscopic submucosal dissection has been explored but is not common. In metastatic LMS radiation and chemotherapy, with doxorubicin or a regimen of gemcitabine with docetaxel, is described. Yet no robust treatment response is demonstrated with available agents. Histopathologic grade, mucosal ulceration, and presence of metastases harbor poor prognosis.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.005 | 0.002 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.009 | 0.003 |
| Insufficient payload (model declined to judge) | 0.005 | 0.004 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".