Bladder-Adherent Primary Appendiceal Carcinoma Masquerading as a Carpeting Rectal Lesion Detected by a Fecal Immunochemical Test: A Case Report
Bibliographic record
Abstract
Introduction: Primary appendiceal carcinoma is rare and comprises up to 1% of all colorectal malignancies. Its invasion into adjacent organs, such as the bladder and rectum, especially as a presenting characteristic, is even less common. Case Presentation: A 75-year-old asymptomatic male tested positive on a screening fecal immunochemical test (FIT). Colonoscopy showed a rectosigmoid tumor and normal appendiceal orifice. Staging MRI surprisingly showed that the cancer was, in fact, of appendiceal origin, coursed posteriorly to invade the rectosigmoid and form adhesions with the urinary bladder. Staging CT did not show metastatic disease. Low anterior resection, en bloc appendectomy, and right hemicolectomy were performed along with cystectomy and ileal conduit. Hematoxylin and eosin stains showed appendiceal adenocarcinoma invading through the appendiceal wall into the rectal muscularis and submucosa. Features of neuroendocrine carcinoma were not identified on immunohistochemistry. This was a colonic type of adenocarcinoma of the appendix. Conclusion: This is a rare case of appendiceal carcinoma invading the rectum and presenting as a positive screening fecal immunochemical test in an asymptomatic individual. We effectively demonstrate the use of preoperative MRI to identify the appendiceal origin of the tumor, as well as to demonstrate the extent of tumor spread, which assisted with operative management and treatment planning.
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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 | 0.004 |
| Meta-epidemiology (narrow) | 0.004 | 0.002 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.005 | 0.003 |
| Science and technology studies | 0.004 | 0.003 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.008 | 0.004 |
| Insufficient payload (model declined to judge) | 0.003 | 0.002 |
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".