Endocrine Abstracts

Background: A recent study of a small series of patients with appendiceal neuroendocrine tumors (ANETs) fulfilling various criteria for right hemicolectomy (RHC) revealed that ≈ 25% may harbor identifiable extra-appendiceal disease. The residual disease might not have been detected using the latest European Neuroendocrine Tumors Society (ENETs) revised pathological criteria.

Aims: To evaluate the latest pathological criteria for completion right hemicolectomy in an extended series of patients with ANETs.

Methods: The medical files of 27 consecutive patients who underwent RHC for ANETs in three tertiary hospital NETs clinics were retrospectively assessed. Demographic, clinical, laboratory data were collected; surgical specimens were reviewed for the indications for completion RHC: tumor diameter of ≥2 cm, tumor location at the appendiceal base, extensive mesoappendiceal invasion (EMI) of >3 mm, vascular invasion (VI) or a KI67 proliferation index of ≥2%.

Results: 5/27 patients were found to have residual disease. In 8/27 patients (30%) the tumor diameter was < 1 cm; the indications for RHC included: tumor presence in surgical margins (3), EMI (5), VI (2), KI67 ≥2% (3); residual disease was present in one patient (13%). In 12/27 patients (44%) the tumor diameter was 1–2 cm; the indications for RHC were as follows: tumor presence in surgical margins (1), EMI (10), VI (2), KI67 ≥2% (2); residual disease was present in two patients (17%). In 7/27 patients (26%) tumor diameter was ≥2 cm. In this subgroup, RHC is accepted practice; the tumor was present in surgical margins (3), EMI (7), VI (5), KI67 ≥2% (5). Residual disease was present in two patients (28%).

Conclusions: In patients with ANETs it is well established that tumor size and the EMI are the most significant factors in taking the decision about the extension of the surgery. Our present data suggests that in the subgroup of patients with a primary tumor size between 1–2 cm (the ‘gray zone’) the risk of residual disease high. Using the latest criteria for RHC, residual disease may be missed in 7% of ANETs patients.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.