Updated staging and patient outcomes in low-grade appendiceal mucinous neoplasms

Insights into the Clinical Prognosis of High-grade Appendiceal Mucinous Neoplasms

High-grade appendiceal mucinous neoplasm (HAMN) is used to describe a rare epithelial neoplasm of the appendix characterized by pushing-type invasion and high-grade cytologic atypia. Its implications regarding lymph node spread and the necessity of right colectomy are currently debate. The objective of the present study was to assess the clinicopathologic characteristics, the risk of lymph node and peritoneal metastasis, and long-term outcomes of patients diagnosed as HAMN in comparison to low-grade appendiceal mucinous neoplasm (LAMN) and appendiceal adenocarcinoma, treated by right hemicolectomy. A total of 443 patients diagnosed with LAMN (n=246), HAMN (n=34), or appendiceal adenocarcinoma (n=163) and who underwent right colectomy with lymph node dissection in all cases within 32 institutions of the French Network for Rare Peritoneal Malignancies (RENAPE) were included. The median age was 56.5 years (range: 21 to 91), and the majority were female (n=250, 56.4%) without difference between groups ( P =0.604). Lymph node metastases were identified in 17.8% of appendiceal adenocarcinoma cases (29/163); none were found among LAMN or HAMN cases. A higher number of lymph nodes were analyzed in those treated for appendiceal adenocarcinoma than LAMN ( P <0.001) and HAMN ( P =0.035). Regarding peritoneal metastasis, a higher proportion of cases were classified as high-grade with/without signet cells in patients treated for HAMN ( P <0.001) and appendiceal adenocarcinoma ( P <0.001) than those treated for LAMN. Among patients with perforation of the appendix, those treated for LAMN had longer overall survival (OS; P <0.001) and progression-free survival (PFS; P <0.0001) than those treated for appendiceal adenocarcinoma or those treated for HAMN; among patients without perforation, those treated for LAMN and HAMN had longer OS ( P =0.042) and PFS ( P =0.012) than those treated for appendiceal adenocarcinoma. No lymph node metastases were observed in patients treated for HAMN, and those without appendix perforation had a similar prognosis to LAMN. This study supports staging HAMN using the same system as LAMN and treating it with appendectomy alone in the absence of appendix perforation.

Low-grade appendiceal mucinous neoplasms: a case series

Appendiceal mucinous neoplasms, including low-grade appendiceal mucinous neoplasms (LAMNs), are infrequent but clinically relevant due to their potential progression to pseudomyxoma peritonei. Timely diagnosis and surgical intervention are critical to preventing complications. We present a case series of three middle-aged men with LAMNs, each of whom exhibited right lower quadrant abdominal pain as their primary symptom. Diagnostic imaging in each case revealed features consistent with appendiceal mucoceles. Pathological findings confirmed LAMN, with varying extents of disease. One patient underwent an open appendectomy for LAMN confined to the appendix, while two required right hemicolectomy due to perforation and extra-appendiceal mucin involvement. LAMNs can be managed effectively through early detection and surgical resection. Complete resection with negative margins results in favorable outcomes and low recurrence rates. More aggressive treatments, including cytoreductive surgery with or without hyperthermic intraperitoneal chemotherapy, are necessary in cases with peritoneal involvement.

Predictors of Recurrence in Nonmetastatic Appendiceal Epithelial Cancers: An Updated Single-Center Experience Over 25 Years

BACKGROUND

Appendiceal epithelial tumors are rare and encompass a broad set of adenocarcinoma histologies, including mucinous (mAC), colonic-type (cAC), and goblet cell (GCA) adenocarcinomas. It has previously been reported that nodal disease predicted recurrence in patients with nonmetastatic appendiceal adenocarcinomas, supporting diagnostic laparoscopy with right hemicolectomy for staging and assessment for risk of recurrence. In this update, we sought to identify predictors of nodal disease on initial diagnostic pathology in nonmetastatic adenocarcinomas.

METHODS

Patients with nonmetastatic appendiceal adenocarcinoma at a single institution from 1994 to 2020 were included. Clinicopathologic characteristics that predict recurrence and lymph node metastasis were analyzed. Workup included staging laparoscopy with right hemicolectomy, seriel imaging and biochemical monitoring.

RESULTS

A total of 147 patients with mAC (18%), cAC (22%), and GCAs (59%) were included. After median follow-up of 53 months, 23 (16%) patients recurred, most commonly in the peritoneal cavity (17/23, 74%). Recurrence rates were higher among node-positive patients (59% vs. 5%, P < 0.001). Nodal disease was more common in mAC (27%) and cAC (37%) than in GCA (11%); however, adenocarcinoma grade was not associated with nodal involvement.

CONCLUSIONS

Nodal metastasis was more common in mAC and cAC compared with GCA and was the only significant predictor of recurrence in appendix cancer.

Acellular Appendix Vermiform Mucinous Neoplasm

Appendiceal neoplasms are usually asymptomatic or associated with mild, nonspecific symptoms. Due to the rarity of the disease and the lack of specific symptoms, this clinical entity escapes the diagnostic consideration of the gynecologist, when women come in with right iliac fossa pain. A case is presented of a 56-year-old woman with a mass in the right small pelvis, which was preoperatively diagnosed as originating from the ovary. An exploratory laparotomy followed in which the uterus and appendages were found to be macroscopically normal, while the mass described above came from the appendix, extended into the anatomical area of the right accessory, and was in contact with the atrophic right ovary. The appendix vermiformis was removed intact. The final pathologic examination confirmed an acellular mucinous tumor of the appendix. Accurate preoperative diagnosis of mucoceles is extremely difficult to make. The formation is discovered in a random imaging test, and the diagnosis is confirmed only intraoperatively.

[Incidental finding of appendiceal mucinous neoplasms]

Low-grade appendiceal mucinous neoplasms (LAMN) are rare and are diagnosed in at least 0.13% of appendectomies in Germany, although significant underreporting is likely. Perforation of the tumors can result in abdominal mucinous collections, so-called pseudomyxoma peritonei (PMP). The challenge in the treatment of LAMN is the adequate approach to the incidental finding of these tumors. If a mucinous neoplasm is preoperatively suspected in cases of an acute condition, usually appendicitis, it must be weighed up whether a conservative approach is justifiable or whether immediate appendectomy is necessary. If this is the case, an intraoperative perforation of the appendix must be avoided and the complete abdominal cavity must be inspected for mucin deposits. If conservative treatment is possible, further treatment should take place at a specialized center. If the neoplasm is first found incidentally during surgery, perforation of the appendix should also be avoided and the entire abdominal cavity should be inspected for a PMP. If a PMP is present cytoreduction and hyperthermic intraperitoneal chemotherapy (HIPEC) should be performed in a specialized center. If LAMN are found during the postoperative histological work-up, it should be evaluated whether a perforation was present and mucin collections are noted in the surgical report. In the case of LAMN without evidence of a PMP, appendectomy is the adequate treatment. In cases of intra-abdominal mucinous collections, samples should be taken and further treatment should be performed at a center with sufficient expertise. An ileocecal resection or oncological hemicolectomy is not indicated. After adequate treatment, all patients should receive a follow-up using cross-sectional imaging (preferably magnetic resonance imaging, MRI) and determination of the tumor markers CEA, CA 19-9 and CA 125.

Low-Grade Appendiceal Mucinous Neoplasm: What Is the Best Treatment?

BACKGROUND

Low-grade appendiceal mucinous neoplasm (LAMN) is an uncommon tumor of the appendix that is usually diagnosed incidentally after surgery. Although LAMN may be asymptomatic, it can rupture and seed mucin and neoplastic epithelium into the peritoneum, causing pseudomyxoma peritonei (PMP).

MATERIALS AND METHODS

Data from 53 patients were retrospectively analyzed. Age, sex, tumor size, margin status, peritoneal carcinomatosis index, surgical procedures, postoperative results with histologic diagnosis, T stage, recurrence, and mortality of the patients were evaluated.

RESULTS

Appendectomy was performed in 37 patients, right hemicolectomy in nine patients, cytoreductive surgery in one patient, and cytoreductive surgery and hyperthermic intraperitoneal chemotherapy in six patients. Recurrence occurred in four patients. Of the patients who developed recurrence, one patient had stage T4a disease, and the other three patients had T4b disease (p<0.001). Eighteen patients had acellular mucin in the serosa and four of these patients developed recurrence (p=0.004). Twelve patients had appendix perforation, and three of these patients had PMP on exploration (p<0.001). The mean survival time was 93.3 months in patients without recurrence and 32 months in patients with recurrence (p=0.021).

CONCLUSIONS

Low-grade appendiceal mucinous neoplasms are rare appendiceal tumors. The appropriate management of this tumor is controversial. T stage, appendix perforation, presence of acellular mucin on the serosa, and surgical margins are risk factors for the development of PMP. Appendectomy is considered sufficient when there are no risk factors for Tis (LAMN) and T3 disease. Right hemicolectomy may be sufficient if there are no risk factors for T4a disease, but cytoreductive surgery and hyperthermic intraperitoneal chemotherapy seem to be the most appropriate treatments in the presence of the stated risk factors for T4b disease.

Staging of appendiceal mucinous neoplasms: challenges and recent updates

Low-grade appendiceal mucinous neoplasms are unique tumors of the appendix, characterized by low-grade mucinous epithelium with villiform, undulating, or flat architecture. These tumors lack infiltrative growth or destructive invasion, but can extend into the appendiceal wall by a "pushing" pattern of invasion, with a broad front that can mimic a diverticulum. These neoplasms have a propensity for peritoneal dissemination, resulting in the clinical presentation of pseudomyxoma peritonei. The pathologic staging of these neoplasms is challenging and fraught with confusing terminology and numerous classification systems. This review focuses on the AJCC pathologic staging of these tumors with a focus on challenging situations.

High-Grade Appendiceal Mucinous Neoplasm: Clinicopathologic Findings in 35 Cases

CONTEXT.—

High-grade appendiceal mucinous neoplasm (HAMN) is a relatively recently introduced term describing a rare epithelial neoplasm of the appendix that demonstrates pushing-type invasion but high-grade cytologic atypia. It remains understudied.

OBJECTIVE.—

To describe clinicopathologic features of HAMNs.

DESIGN.—

We identified 35 HAMNs in a multi-institutional retrospective study. Clinical and histologic features were reviewed in all cases, as well as molecular features in 8 cases.

RESULTS.—

Patients were 57 years of age on average and most commonly presented with abdominal/pelvic pain. Histologically, 57% of the tumors showed widespread high-grade features. Architectural patterns in high-grade areas included flat, undulating, or villous growth, and occasionally micropapillary, cribriform, or multilayered growth. Thirteen cases had intact serosa, and the remaining 22 perforated the serosa, including 7 with peritoneal acellular mucin beyond appendiceal serosa and 10 with grade 2 pseudomyxoma peritonei. Molecular abnormalities included KRAS mutations in 7 cases and TP53 mutations in 4. No tumor confined to the appendix recurred. Two patients without pseudomyxoma peritonei at initial presentation developed pseudomyxoma on follow-up. Among 11 patients who presented with pseudomyxoma peritonei, 5 died of disease and 3 were alive with disease at last follow-up.

CONCLUSIONS.—

HAMNs have a similar presentation to low-grade appendiceal mucinous neoplasm, and similar stage-based prognosis. When they spread to the peritoneum, they typically produce grade 2 pseudomyxoma peritonei, which may be associated with a worse prognosis than classical grade 1 pseudomyxoma peritonei.

Clinicopathologic parameters and outcomes of mucinous neoplasms confined to the appendix: a benign entity with excellent prognosis

Appendiceal mucinous neoplasms (AMNs), characterized by expansile or "pushing" growth of neoplastic epithelium through the appendix wall, are sometimes accompanied by peritoneal involvement, the extent and grade of which largely determine clinical presentation and long-term outcomes. However, the prognosis of tumors entirely confined to the appendix is still debated and confusion remains regarding their biologic behavior and, consequently, their clinical management and even diagnostic nomenclature. We evaluated AMNs limited to the appendix from 337 patients (median age: 58 years, interquartile range (IQR): 47-67), 194 (57.6%) of whom were women and 143 (42.4%) men. The most common clinical indication for surgery was mass or mucocele, in 163 (48.4%) cases. Most cases (N = 322, 95.5%) comprised low-grade epithelium, but there were also 15 (4.5%) cases with high-grade dysplasia. Lymph nodes had been harvested in 102 (30.3%) cases with a median 6.5 lymph nodes (IQR: 2-14) per specimen for a total of 910 lymph nodes examined, all of which were negative for metastatic disease. Histologic slide review in 279 cases revealed 77 (27.6%) tumors extending to the mucosa, 101 (36.2%) to submucosa, 33 (11.8%) to muscularis propria, and 68 (24.4%) to subserosal tissues. In multivariate analysis, deeper tumor extension was associated with older age (p = 0.032; odds ratio (OR): 1.02, 95% confidence intervals (CI): 1.00-1.03), indication of mass/mucocele (p < 0.001; OR: 2.09, CI: 1.41-3.11), and wider appendiceal diameter, grossly (p < 0.001; OR: 1.61, CI: 1.28-2.02). Importantly, among 194 cases with at least 6 months of follow-up (median: 56.1 months, IQR: 24.4-98.5), including 9 high-grade, there was no disease recurrence/progression, peritoneal involvement (pseudomyxoma peritonei), or disease-specific mortality. These data reinforce the conclusion that AMNs confined to the appendix are characterized by benign biologic behavior and excellent clinical prognosis and accordingly suggest that revisions to their nomenclature and staging would be appropriate, including reverting to the diagnostic term mucinous adenoma in order to accurately describe a subset of them.