Macroscopic and microscopic characteristics of low grade appendiceal mucinous neoplasms (LAMN) on appendectomy specimens and correlations with pseudomyxoma peritonei development risk

Low back pain as main symptom in Low-grade Appendiceal Mucinous Neoplasm (LAMN): A case report

BACKGROUND

Low back pain is the leading cause of disability worldwide. It is also the main cause of the limitation of activities and absence from work in much of the world and a cause of great economic burden. The greatest percentage of low back pain is classified as nonspecific (i.e. not attributable to a defined pathology), while the others may concern specific pathologies of the lumbar region or suggest pathologies of non-musculoskeletal origin. Consequently, evaluating any signs and symptoms mimicking musculoskeletal conditions is crucial.

CASE DESCRIPTION

This case report describes a 64-year-old female patient who first presented to the physiotherapist with two weeks of low back pain, complaining of a different clinical presentation than the previous episodes. The patient's pain started spontaneously and was located in the lumbar region over a diffuse area. Symptoms were constant throughout the day and did not change with movement. Based on the examination findings, the physiotherapist decided to make an urgent referral to the patient's General Practitioner.

OUTCOMES

Following ultrasound examination and Computed Tomography scan, an 8.5 cm mass was confirmed in the abdominal region. It was surgically removed, and a histological diagnosis of Low-grade Appendiceal Mucinous Neoplasm (LAMN) was made.

CONCLUSION

The physiotherapist's evaluation and decision-making process was fundamental in the patient's referral due to suspected pathology not within the scope of practice. This revealed a rare condition, which, according to the existing literature, is usually diagnosed in the event of collateral imaging findings or upon presentation of complex and/or emergency clinical pictures.

Low-grade appendiceal mucinous neoplasm: A case report

RATIONALE

Low-grade appendiceal mucinous neoplasm (LAMN) is a clinically rare tumor that predominantly occurs in females and presents with nonspecific symptoms, often resulting in misdiagnosis. While postoperative pathology remains the gold standard for diagnosis, accurate preoperative identification through various diagnostic methods is essential for effective treatment planning. To raise awareness of this condition, we present a case of a middle-aged male diagnosed with LAMN.

PATIENT CONCERNS

A 52-year-old male presented to outpatient clinic with right lower abdominal pain lasting 1 day. He described the pain as continuous cramping, exacerbated by movement and coughing, with associated nausea.

DIAGNOSIS

Physical examination revealed tenderness in the right lower quadrant and a palpable mass measuring approximately 6.5 cm × 5.0 cm, with poor definition and limited mobility. An elevated white blood cell count (16.2 × 109/L) and a mixed cystic and solid mass were noted, prompting admission for further evaluation. Further, abdominal enhanced computed tomography revealed a mixed-density lesion in the right ileocecal region, measuring approximately 6.5 cm × 5.0 cm. This finding was suggestive of an appendiceal mucinous neoplasm, with mucinous adenocarcinoma remaining a possibility that could not be excluded.

INTERVENTIONS

The patient underwent a laparoscopic right hemicolectomy on June 5, 2024, and the gross specimen showed: a 6.5 cm × 5.0 cm mass was found in the appendix area on the surface of the intestinal tube, a large amount of jelly was found after incision, and the mass was connected to the intestinal cavity.

OUTCOMES

The patient recovered well after surgery, the abdominal drainage tube was pulled out on the 8th day after surgery, and the patient was discharged on the 13th day after surgery. Postoperative examination showed LAMN and mucus accumulation in the wall of the appendix with a foreign body giant cell reaction, acute attack of chronic appendicitis, and suppurative inflammation with peripheral inflammation. Postoperative diagnosis: LAMN; acute chronic appendicitis attack.

LESSONS

As a rare clinical gastrointestinal tumor, LAMN lacks specific clinical manifestations, and its diagnosis depends on postoperative examination; however, the indications for surgery are clear and the clinical prognosis is good. The key to surgery is to protect the tumor body to avoid rupture and cause the development of peritoneal pseudomyxoma (PMP).

Prophylactic cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for low-grade appendiceal mucinous tumors with early and limited disease after completely removed

The necessity of prophylactic cytoreductive surgery (PCRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) for low-grade appendiceal mucinous neoplasms (LAMN) after complete removal is still controversial. This study aims to determine the role of PCRS + HIPEC and identify optimal strategies for managing these patients. One hundred fifty-nine patients who sought medical advice at Aerospace Center Hospital were retrospectively analyzed from January 2011 to December 2021. All the patients were divided into the PCRS group and the observation group. The data of surgical specimens and pathology was collected, and the effect on recurrence-free survival (RFS) was analyzed. Of these 159 patients, 88 were in the PCRS group, and 71 were in the observation group. The median follow-up time was 38 months. Seven patients recurred and developed into pseudomyxoma peritonei, 1 in the PCRS group and 6 in the observation group. The analysis of RFS showed that patients who underwent PCRS (P = .01) and HIPEC (P = .01) had better survival. After multivariate analysis, the surgical specimen accompanied by disseminated peritoneal adenocarcinoma was identified as an independent prognostic factor for RFS. In the study of surgical resection content, patients with greater omentum (P = .01) and bilateral fallopian tubes and ovaries of women (P = .002) resection had a more prolonged RFS with statistical significance. The research indicated that PCRS + HIPEC could prevent recurrence. Therefore this treatment were necessary for LAMN after complete removal in patients with a high risk of recurrence. However, it was not proven to be an independent factor for RFS, and a multicenter, prospective, randomized trial was need to definitively address the role of PCRS + HIPEC for LAMN after complete resection.

Diagnostic difficulties in the differentiation between an ovarian metastatic low‑grade appendiceal mucinous neoplasm and primary ovarian mucinous cancer: A case report and literature review

Low-grade appendiceal mucinous neoplasm (LAMN) is a tumor that primarily originates from the appendix and belongs to the family of appendiceal mucinous neoplasms (AMNs). In 50% of female patients, AMNs (particularly LAMNs) have a tendency to metastasize to organs in the genital tract, where the neoplasm can mimic the features of primary ovarian mucinous cancer (POMC). The present case report reviewed the difficulties in differentiating between these two types of tumors. In the present case report, a 61-year-old female patient was admitted to the Second Department of Gynecological Surgery and Gynecological Oncology, University Clinical Hospital no. 4 at Lublin Medical University (Lublin, Poland) with the diagnosis of a right ovarian mass. After performing ultrasound and computed tomography (CT) scans and laboratory analysis, the patient underwent total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, appendectomy and resection of the Douglas peritoneum. Notably, the postoperative pathological assessment revealed LAMN with metastases to the right ovary and omentum. Immunohistochemically, cytokeratin 20 and caudal type homeobox 2 both stained positively, whereas paired box gene 8 stained negatively. After surgery, the patient received the recommended hyperthermic intraperitoneal chemotherapy at the Department of Surgical Oncology at Lublin Medical University. After 1 year, a CT scan was performed, which indicated no evidence of recurrent disease. In conclusion, observations from the present case report suggest that gynecologists should be conscious of the possibility of malignancies of gastrointestinal origin in cases of ovarian tumors instead of making direct assumptions of POMC. If the mucinous mass involves the base of the appendix or if there is a suspicion of positive margins, then cytoreductive surgery and right-sided hemicolectomy must be performed. In addition, identifying the origin of mucinous tumors in the right ovary and/or the appendix requires the histopathological examination of a panel of markers using immunohistochemistry.

Risk stratification of surveillance for low-grade appendiceal mucinous neoplasms

BACKGROUND

Low-grade appendiceal mucinous neoplasms (LAMNs) can progress to pseudomyxoma peritonei (PMP). The incidence and risk factors for recurrence are unclear, and there is a lack of consensus on the need and duration of surveillance imaging.

METHODS

Patients at the Mayo Clinic in Rochester, Minnesota, with a histologic diagnosis of LAMNs confined to the appendix and limited involvement of the right lower quadrant from 1992 to 2023 were included. Associations between recurrence and risk factors were assessed using Kaplan-Meier curves and Cox proportional hazards regression.

RESULTS

A total of 125 patients with LAMNs underwent abdominal imaging surveillance for a median of 51.2 months (IQR, 26-92). Of note, 5 patients (4%) recurred, all of which were PMP. Overall, the 5- and 10-year cumulative recurrence incidence rates were 3% and 6%, respectively. The median time to recurrence was 24 months (IQR, 23-87). Only LAMNs limited to the right lower quadrant and LAMN tumor size of <2 cm were associated with recurrence (P < .05). The 5- and 10-year cumulative recurrence risks were 12% and 30%, respectively, for the 21 patients with either risk factor. Only 1% of patients without these 2 risk factors developed a recurrence at 10 years.

CONCLUSION

The overall recurrence risk of LAMN after resection is low. Appendectomy is sufficient for LAMN. Select patients with acellular mucin confined to the right lower quadrant and a tumor size of <2 cm are at higher risk of recurrence. Thus, long-term surveillance is recommended for high-risk individuals. Conversely, LAMNs without risk factors can be safely observed expectantly.

Origin and survival outcomes of Pseudomyxoma peritonei-A retrospective study

BACKGROUND

Pseudomyxoma peritonei (PMP) is an unusual clinical condition typically presenting with widespread mucinous neoplastic lesions within the peritoneum resulting in gelatin material-rich ascites. It was first described by Werth in 1884. Ever since, its clinical presentation, definition, site of origin, and prognosis have been a subject of debate. However, many histopathologic, immunohistochemical, and genetic studies have attempted to locate the primary lesion in the appendix in both genders.

OBJECTIVES

To analyze the histological origin and survival outcomes of pseudomyxoma peritonei in patients treated at a regional cancer center.

MATERIALS AND METHODS

Fifteen cases of PMP were diagnosed during the five-year study period. The demographic and clinicopathological details were retrieved; the slides were reviewed and histological parameters reassessed. Descriptive statistics were used to express proportions. Continuous variables were recorded as mean (SD) or median (IQR). Kaplan-Meier (KM) curve was used to estimate overall survival.

RESULTS

Mean age for PMP was found to be 47.5 years for low grade Mucinous Carcinoma Peritonei (MCP), 54.2 years for high grade MCP, and 58 years for high grade MCP with signet ring cells. Most common overall presentation was abdominal distension in 53.3% (8/15) of cases, followed by acute appendicitis in 20% (3/15) cases. PMP was detected synchronous with the primary tumor in 9/15 cases (60%). Primary lesion in the appendix was grossly identified in 7/15 cases, while it was not explored in the remaining eight cases. Yet, by combined clinical, radiological, histopathological, and immunohistochemical analysis, we identified that most of the cases (14/15) had an appendiceal origin (93.3%). The overall survival for 12 months was 50% and for 18 months was 37%.

CONCLUSION

The surgeon and radiologist may well bear in mind the most common possibility of an appendiceal origin for PMP and resect the appendix, irrespective of the presence of a grossly or radiologically detectable lesions. We emphasize that immunohistochemistry helped to detect the site of origin even when the primary was occult.

Ovarian Causes of Pseudomyxoma Peritonei (PMP)-A Literature Review

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare, progressive, slowly growing, inadequately understood neoplasm with a 5-year progression-free survival rate of as low as 48%. It is characterized by varying degrees of malignancy and the production of mucinous and gelatinous structures. Typically, the development of pseudomyxoma peritonei is associated with the rupture of appendiceal mucinous tumors and other gastrointestinal or ovarian mucinous tumors. The goal of our literature review was to identify various aspects that characterize the ovarian causes of pseudomyxoma peritonei.

MATERIALS AND METHODS

The authors performed an extensive literature search between 1 February 2024 and 2 March 2024 on the following databases: Pubmed, Scopus, Oxford Journals, and Reaxys, and the findings were summarized into seven main clinical and paraclinical situations.

RESULTS

According to our research, the main instances in which pseudomyxoma peritonei can be triggered by an ovarian cause are the following: (1) mucinous cystadenoma; (2) mucinous ovarian cancer; (3) colon cancer with ovarian metastasis; (4) malignant transformation of an ovarian primary mature cystic teratoma; (5) appendiceal mucocele with peritoneal dissemination mimicking an ovarian tumor with peritoneal carcinomatosis; (6) mucinous borderline tumor developing inside an ovarian teratoma; and (7) the association between a mucinous bilateral ovarian cancer and a colonic tumor.

CONCLUSIONS

In our study, we aimed to provide a comprehensive overview of the ovarian causes of pseudomyxoma peritonei, including its epidemiology, imagery characteristics, symptoms, current treatment, and promising future therapies, in the hopes of finding feasible solutions, as a lack of understanding of this mucus-secreting malignant disease increases the risk of delayed diagnosis or uncontrolled deterioration.

Does a Positive Appendiceal Resection Margin in Low-Grade Appendiceal Mucinous Neoplasms, Warrant Additional Surgery? Our Institution Experience and Literature Review

BACKGROUND

Management of low-grade appendiceal mucinous neoplasm (LAMN) with positive resection margin is controversial. Some guidelines recommend surgical reexcision, whereas others recommend a conservative approach. The purpose of our study was to determine whether involvement of the resection margin by LAMN is a risk factor for local recurrence requiring additional surgery.

DESIGN

This is a retrospective study (January 2000-December 2020) of uncomplicated LAMNs with neoplastic epithelium or dissecting mucin at the resection margin. For cases treated with additional surgery, the presence of residual tumor was evaluated. Clinical follow-up was attained in all cases. We also conducted a literature review.

RESULTS

The study investigated 98 patients. Eight with median age of 67 (range: 45-91) years had a LAMN involving the resection margin (8.2%). Five of eight LAMNs (62.5%) with neoplastic epithelium at the margin underwent surgery, and no residual neoplasm was identified. The other three cases were followed conservatively, and no patient developed recurrence (follow-up: 18-69 months with a mean of 45 months). In a review of the literature, we identified 52 LAMNs with positive margin. Although three cases had acellular mucin and one residual LAMN in the reexcision specimen (7.7%), neither of these four cases or any of the other 46 followed conservatively had recurrence of disease.

CONCLUSIONS

These data suggest that for patients with uncomplicated LAMN confined to the appendix, the involvement of the appendiceal margin does not necessary lead to recurrence of LAMN, and a conservative management is a reasonable alternative.

[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.

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.

OUP accepted manuscript

The differential diagnosis of abdominal pain is wide as both benign and malignant pathologies must be considered. There are currently no published case reports of low-grade appendiceal mucinous neoplasms (LAMNs) mimicking perforated diverticulitis. LAMNs are a heterogenous group of tumours, with no consensus treatment algorithm based on stage and histology. In this case report, we discuss a patient who presented emergently with generalized peritonism, with a diagnosis of perforated diverticulitis made on computed tomography scan. At laparotomy, a perforated appendix was identified, with histopathology identifying a perforated LAMN. This case highlights the importance of considering this rare but increasing incidence tumour when operative management is being planned.

Incidentally found mucinous epithelial tumors of the appendix with or without pseudomyxoma peritonei: diagnostic and therapeutic algorithms based on current evidence

Mucinous appendiceal tumors with or without the pseudomyxoma peritonei (PMP) syndrome are rare, but often present as an incidental finding. The confusing histology and lack of large prospective trials result in a considerable diagnostic and therapeutic challenge in these patients. We propose treatment algorithms in patients with incidentally found mucinous epithelial appendiceal tumors, with or without PMP, based on the currently available evidence. The therapeutic approach should take into account the histology and grade of the primary appendix tumor, as well as those of the associated peritoneal disease.