Appendiceal sessile serrated lesions are distinct from their right-sided colonic counterparts and may be precursors for appendiceal mucinous neoplasms

Rate of Neoplasia in Patients with Complicated Acute Appendicitis Managed Nonoperatively: A Prospective Study

BACKGROUND

Recent studies suggest the rate of neoplasia in patients with complicated acute appendicitis initially managed nonoperatively is higher than previously reported.

OBJECTIVE

This study aimed to determine the incidence and predictors of neoplasia in patients with complicated appendicitis treated nonoperatively.

METHODS

We conducted a prospective cohort study of all patients who presented to a tertiary care center with acute appendicitis between 2019 and 2023. Patients with complicated appendicitis treated nonoperatively were included in the study cohort. Patient demographics, clinical course, radiological findings, and pathologic information were collected. The primary outcome was rate of neoplasia. Multivariable logistic regression analysis was performed to identify predictors of appendiceal neoplasia.

RESULTS

In total, we identified 1166 patients with acute appendicitis, of whom 75 patients had complicated appendicitis treated nonoperatively (median age 51 years [interquartile range 38-68]; 36 [48%] were female). Fifty-four (72%) patients had their appendix removed due to failure of nonoperative management, recurrent symptoms, suspicion of neoplasia, or elective surgery. The neoplasia rate among patients with complicated appendicitis initially treated nonoperatively was 16.0% (12/75). Two patients with neoplasia were younger than 40 years of age. Suspicion of malignancy on initial imaging was associated with an increased risk of appendiceal neoplasia (odds ratio 8.13, 95% confidence interval 1.20-55.15; p = 0.03). Age, sex, and appendiceal diameter were not significantly associated with appendiceal neoplasia.

CONCLUSIONS

The high rate of appendiceal neoplasia in patients with complicated appendicitis treated nonoperatively should be a factor in decision making for interval appendectomy for patients of all ages.

Connecting the dots: Low-grade appendiceal mucinous neoplasms and serrated polyps in the appendix

OBJECTIVE

This study aimed to examine the relationship between low-grade appendiceal mucinous neoplasms (LAMNs) and serrated polyps (SPs) of the appendix, both characterized by KRAS mutations and overlapping morphologic features.

METHODS

We analyzed 27 cases of LAMN and 24 cases of SP from archival records, reviewed pathology, and performed molecular analysis on select cases. Four cases initially diagnosed as LAMN were excluded for not meeting diagnostic criteria, and 1 SP case was reclassified as LAMN.

RESULTS

Microscopic evaluation revealed serrated architecture in 8 (29.6%) of 27 LAMNs: 4 hyperplastic polyp-like, 2 sessile serrated lesion-like (SSL), and 1 traditional serrated adenoma-like (TSA). One case exhibited both SSL- and TSA-like areas. Among SPs, 3 (12.5%) of 24 cases showed morphologic overlap with LAMN due to cytoplasmic mucin, flattened mucosa, and conventional adenoma-like features; all were grossly visible. KRAS was the most common mutation in LAMNs with serrated architecture (4/4, 100%), 1 classic LAMN, and 1 SP with dysplasia and associated signet-ring cell carcinoma.

CONCLUSIONS

Serrated polyps and LAMNs likely represent a biological continuum, sharing key features such as KRAS mutations and morphologic overlap. Our findings underscore the need for careful molecular and histopathologic evaluation in diagnosing these neoplasms.

A practical guide to serrated appendiceal lesions

Several neoplastic and non-neoplastic proliferations of the appendix can show varying degrees of serrated epithelial architecture. Of these, diffuse mucosal hyperplasia is most common, followed in frequency by low-grade mucinous and serrated neoplasms. It is important to distinguish serrated appendiceal neoplasms from their potential mimics because these entities may be managed differently. Diffuse mucosal hyperplasia is a non-neoplastic change that usually develops in the setting of resolving appendicitis and requires no further therapy or surveillance, and serrated neoplasms confined to the mucosa are adequately treated by appendectomy alone. On the other hand, low-grade appendiceal mucinous neoplasms may require surveillance, and those with extra-appendiceal spread differ from adenocarcinomas arising from serrated neoplasms with respect to both treatment and prognosis. Low-grade mucinous neoplasms in the peritoneum are frequently amenable to peritoneum-directed therapies alone, while adenocarcinomas derived from serrated neoplasms often spread to both regional lymph nodes and the peritoneum, potentially requiring right colectomy and systemic chemotherapy. The purpose of this review is to summarize the literature regarding the clinical and pathologic features of appendiceal lesions that show epithelial serration and provide the reader with helpful tips to distinguish serrated neoplasms from their mimics.

Occult appendix pathology in patients undergoing colorectal cancer resection and prophylactic appendectomy

BACKGROUND

The risk-benefit balance of prophylactic appendectomy in patients undergoing left colorectal cancer resection is unclear. The aim of this report is to assess the proportion of histologically abnormal appendices in patients undergoing colorectal cancer resection in a unit where standard of care is appendectomy, with consent, when left-sided resection is performed.

METHODS

A retrospective study on a prospectively collected database was conducted in a single tertiary-care center. Overall, 717 consecutive patients undergoing colorectal cancer resection between January 2015 and June 2021 were analyzed. The primary outcome was the proportion of histologically abnormal appendix specimens at prophylactic appendectomy. The secondary outcome was complications from prophylactic appendectomy.

RESULTS

Overall, 576/717 (80%) patients had appendectomy at colorectal cancer surgery. In total, 234/576 (41%) had a right-/extended-right hemicolectomy or subtotal colectomy which incorporates appendectomy, and 342/576 (59%) had left-sided resection (left-hemicolectomy, anterior resection or abdominoperineal excision) with prophylactic appendectomy. At definitive histology, 534/576 (92.7%) had a normal appendix. The remaining 42/576 (7.3%) showed abnormal findings, including: 14/576 (2.4%) inflammatory appendix pathology, 2/576 (0.3%) endometriosis, 8/576 (1.4%) hyperplastic polyp, and 18/576 (3.1%) appendix tumors, which encompassed six low-grade appendiceal mucinous neoplasms (LAMNs), three carcinoids, and nine serrated polyps. In the 342 patients who had prophylactic appendectomy, 10 (2.9%) had a neoplasm (two LAMN, three carcinoids, and five serrated polyps). There were no complications attributable to appendectomy.

CONCLUSION

Occult appendix pathology in patients undergoing colorectal cancer resection is uncommon when prophylactic appendectomy was performed. However, approximately 3% of patients had a synchronous appendix neoplasm.

Appendiceal lesions in serrated polyposis patients are easily overlooked but only seldomly lead to colorectal cancer

BACKGROUND

Serrated polyposis syndrome (SPS) is the most prevalent colonic polyposis syndrome and is associated with an increased colorectal cancer risk. A recent study in resected appendices of SPS patients reported that 6/23 (26.1 %) of identified serrated polyps had histological dysplasia. We evaluated the prevalence and clinical relevance of appendiceal lesions in a large SPS cohort.

METHODS

Prospective data from 2007 to 2020 for a cohort of 199 SPS patients were analyzed. Data were retrieved from endoscopy and pathology reports. Patients who underwent (pre)clearance colonoscopies, surveillance colonoscopies, or colorectal surgery including the appendix were separately evaluated for the presence of appendiceal lesions. The primary outcome was the prevalence of adenocarcinomas and serrated polyps/adenomas with advanced histology in the surgery group.

RESULTS

171 patients were included, of whom 110 received endoscopic surveillance and 34 underwent surgery. Appendiceal lesion prevalence in the surgery group was 14 /34 (41.2 %, 95 %CI 24.7 %-59.3 %); none were advanced on histology. Detection rates in the (pre)clearance group were 1 /171 (0.6 %, 95 %CI 0.01 %-3.2 %) for advanced and 3 /171 (1.8 %, 95 %CI 0.04 %-5.0 %) for nonadvanced appendiceal lesions, all of which were sessile serrated lesions. During 522 patient-years of surveillance, no advanced appendiceal lesions were detected at endoscopy, and in 1 /110 patients (0.9 %, 95 %CI 0.02 %-5.0 %) was a nonadvanced lesion detected.

CONCLUSION

Appendiceal lesions are common in SPS patients. The discrepancy between the endoscopic detection rate of appendiceal lesions and the reported prevalence in surgically resected appendices suggests a substantial miss-rate of appendiceal lesions during colonoscopy. Advanced appendiceal lesions are however rare and no appendiceal adenocarcinomas occurred, implying limited clinical relevance of these lesions.