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Low-grade appendix tumors often over-diagnosed as invasive cancer
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Pathologists are often over-diagnosing cases of low-grade appendiceal mucinous neoplasm as invasive appendiceal adenocarcinoma, according to recent study data.
Investigators said this finding is significant as the classification of these mucinous appendix tumors — which can lead to the rare cancer syndrome pseudomyxoma peritonei — strongly influence a patient’s prognosis and treatment.
“Appendix cancer remains extremely challenging for proper pathological classification of tumor type,” Mark A. Valasek, MD, PhD, assistant professor of pathology at UC San Diego School of Medicine, said in a press release. “This is in part because the appendix can harbor not only invasive cancer, but also an enigmatic and confusing low-grade malignancy called LAMN. In addition, the literature on classification of appendix cancer utilizes inconsistent terminology and is constantly evolving. Our findings highlight a critical need for universally accepted criteria to diagnose appendix tumors to help pathologists separate benign, low grade and invasive tumors.”
Valasek and colleagues from the UC San Diego Moores Cancer Center reviewed pathology charts from 2014-2015 and identified 46 cases of appendiceal lesions diagnosed by an external pathologist and then referred to UC San Diego Health. They assessed diagnostic agreement between the reference pathologists and the originating pathologists, who were mostly from non-academic, mid-sized practices and lacked subspecialty training in GI pathology.
The originating pathologists diagnosed half of these cases as adenocarcinoma and half as LAMN, while the reference pathologists diagnosed 28.3% of the cases as adenocarcinoma, 63% as LAMN and 8.7% as ruptured simple mucocele. Therefore, pathologists agreed on an invasive cancer diagnosis 56.5% of the time, and overall interobserver agreement was moderate at 71.7%. All the disagreement in diagnosis was due to over-interpretation, and 65.5% of the LAMN cases were either over-interpreted as adenocarcinoma or were inaccurately risk-stratified.
“A second evaluation of appendiceal lesions changed the diagnosis and therefore management of a significant number of patients,” Andrew M. Lowy, MD, professor of surgery and chief of the division of surgical oncology at UC San Diego Moores Cancer Center, said in the press release. “It is important for someone with expertise in appendix cancer to evaluate pathology reports for the benefit of patients. In addition, recently published guidelines may help facilitate improvement of diagnostic interpretations and reduce over-interpretation and potential overtreatment.”
The researchers have included these guidelines and a diagnostic checklist in their study manuscript. – by Adam Leitenberger
Disclosures: The researchers report no relevant financial disclosures.
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