Mucinous appendiceal neoplasms and pseudomyxoma peritonei: Morphological and clinical findings, differential diagnosis, and prognosis

Background: Low-grade appendiceal mucinous neoplasms (LAMN) of the appendix have bland cytological features and well-differentiated morphology. Despite this, they may cause a pseudomyxoma peritonei (PMP) disease characterized by mucinous deposits in the peritoneal cavity and may exhibit malignant behavior. Aims and Objectives: In this study, we evaluated the clinical course and histopathological findings of LAMN. The rate of progression to PMP, factors affecting its development, and the clinical course of cases with PMP were investigated. Materials and Methods: Twelve thousand and forty-seven cases who underwent appendectomy were reviewed, and 71 mucinous lesions cases whose slides are in our archive were included in the study. Histopathological findings were re-evaluated. Morphological findings that guide the differential diagnosis, the clinical course of the patients, and factors affecting PMP development were determined. Results: The cases were divided into group 1 non-neoplastic (9.9%), group 2 benign (18.3%), group 3 LAMN (60.6), and group 4 malignant neoplasms (11.3%). Age, gender, appendix diameter, gross appearance, epithelial characteristics, and presence of microcalcification were significantly different between the patient groups. The presence of mucin in the ileocecal region was found to be significant in the development of PMP. It was observed that the additional procedure performed after the appendectomy did not prevent a recurrence. Conclusion: LAMNs are lesions with characteristic findings and different behaviors. The only method to distinguish from the lesions included in the differential diagnosis is to interpret the histopathological findings correctly. Additional operations after appendectomy do not contribute to preventing recurrence.

Abordaje laparoscópico de la neoplasia mucinosa apendicular de bajo grado / Laparoscopic approach of low-grade appendiceal mucinous neoplasm

RESUMEN Las neoplasias mucinosas apendiculares son infrecuentes y se clasifican en neoplasias mucinosas de bajo grado, de alto grado y adenocarcinoma mucinoso. Se consideran precursoras del pseudomixoma peritoneal, caracterizado por la acumulación de mucina dentro de la cavidad abdominal. Informamos tres casos de neoplasia mucinosa apendicular de bajo grado, dos varones y una mujer, que presentaron dolor abdominal agudo, diagnosticados preoperatoriamente mediante tomografía y que fueron manejados con un abordaje laparoscópico (apendicectomía, resección parcial de ciego y colectomía derecha, respectivamente). Los tres casos tuvieron una buena evolución posoperatoria y no hubo complicaciones. Se concluye que las neoplasias mucinosas apendiculares son raras y no tienen una presentación clínica específica. El abordaje laparoscópico es una opción segura y factible. La frecuencia y la duración del seguimiento de estos pacientes es motivo de controversia.

ABSTRACT Appendiceal mucinous neoplasms are rare and are classified in low-grade mucinous neoplasm, high-grade mucinous neoplasm and mucinous adenocarcinoma. They are considered precursors of pseudomyxoma peritonei, characterized by the accumulation of mucin within the abdominal cavity. We report three cases of low-grade appendiceal mucinous neoplasm, two men and one woman, who presented with acute abdominal pain. The diagnoses were made preoperatively by computed tomography scan and the tumors were managed through laparoscopic approach (appendectomy, partial resection of the cecum and right colectomy, respectively). The three patients evolved with favorable postoperative outcome without complications. Appendiceal mucinous neoplasms are rare without specific clinical presentation. The laparoscopic approach is a safe and feasible option. The frequency and duration of surveillance in these patients are still controversial.

Neoplasia mucinosa apendicular / Appendiceal mucinous neoplasms

RESUMEN La neoplasia mucinosa apendicular es una entidad poco frecuente que representa el 0,2 al 0,7% de todas las apendicectomías. La forma de presentación más frecuente es el hallazgo incidental. También puede diagnosticarse du rante el estudio de un dolor abdominal crónico en el cuadrante inferior derecho o, de manera retros pectiva, por el hallazgo en la anatomía patológica en el marco de una apendicitis aguda. La apendicectomía es el tratamiento indicado; la técnica tiene como objeto impedir la perforación del apéndice para evitar el vuelco a la cavidad peritoneal de moco o células neoplásicas y de esa manera prevenir el desarrollo del pseudomixoma peritoneal.

ABSTRACT Appendiceal mucinous neoplasms are rare and represent 0.2-0.7% of all appendectomies. They usual present as an incidental finding. The diagnosis can be made during the evaluation of chronic abdomi nal pain in the right lower quadrant or may emerge in the pathology report in the setting of an acute appendicitis. Appendectomy is the treatment of choice and care must be taken to avoid perforation of the appendix with dissemination of neoplastic cells or mucus into the peritoneum and thus prevent the develop ment of pseudomyxoma peritonei.

Clinicopathological analysis and surgical strategy of primary appendiceal neoplasms / 中华胃肠外科杂志

Objective: To investigate the clinicopathological features, surgical methods and prognosis of primary appendiceal neoplasms. Methods: A descriptive case series study was performed. Clinical data of patients diagnosed with primary appendiceal neoplasms in Peking University First Hospital from 2006 to 2017 were retrospectively analyzed. Patients who underwent surgery and were confirmed as appendiceal neoplasms by postoperative pathology were included. Cases of cecal tumor invading the appendix and other organ tumors implanting in the appendix and cases of recurrent appendix tumors were excluded Pathological classification was based on the 4th edition of the WHO classification of digestive tract tumors (2010 edition), and the efficacy of operation methods of low grade appendiceal mucinous neoplasm (LAMN) were analyzed. Results: A total of 115 patients were enrolled, including 52 males and 63 females with a median age of 59 (51, 71) years. Clinical symptoms usually manifested as dormant pain in the right lower quadrant, migrating right lower abdominal pain, fever and bloating. Twenty-four cases were accidentally discovered during surgery, and 21 cases were found by physical examination. The preoperative diagnosis rate of CT and ultrasound was 40.2% (43/107) and 25.5% (24/94) respectively. The postoperative pathological types contained 83 cases of LAMN, 12 cases of mucinous adenocarcinoma, 9 cases of appendiceal neuroendocrine neoplasms (aNEN), 2 cases of mucinous adenocarcinoma with signet ring cells, 3 cases of serrated adenoma, 2 cases of goblet cell carcinoid, 2 cases of lymphoma, 1 case of leiomyoma and 1 case of schwannomas. All the patients underwent surgical resection, including 41 cases of appendectomy, 21 cases of partial cecectomy, 48 cases of right hemicolectomy, and 5 cases of combined organ resection due to appendiceal tumor infiltration or dissemination. Eighteen cases were diagnosed with pseudomyxoma peritonei (PMP) during operation. A total of 98 patients were enrolled for follow-up. The median follow-up time was 58 (5-172) months. The 5-year disease-free survival (DFS) rate was 84.5% and 5-year overall survival (OS) was 88.2%. Multivariate analysis revealed that high-grade malignancy tumors (HR=25.881, 95% CI: 2.827-236.935, P=0.004) and PMP formation (HR=42.166, 95% CI: 3.470-512.439,P=0.003) were independent risk factors for prognosis. Patients undergoing right hemicolectomy presented longer operation time, more blood loss and higher morbidity of complication as compared to those undergoing appendectomy and partial cecectomy (all P<0.05), while no significant differences in 5-year DFS (P=0.627) and 5-year OS (P=0.718) were found. Conclusions: Primary appendiceal neoplasms usually have no typical features, accompanied with low preoperative diagnosis rate. The common pathological types are LAMN, mucinous adenocarcinoma and aNEN. Appendectomy or partial cecectomy for LAMN may achieve satisfactory prognosis. High-grade malignancy tumors and PMP formation are independent risk factors for prognosis.

Heterotopic ossification in appendiceal mucinous neoplasms: clinicopathological characteristics of 3 cases

Heterotopic bone formation is a very rare event in the gastrointestinal tract including in the appendix. Here we report three cases of heterotopic ossification in appendiceal mucinous neoplasms, one occurring in an appendiceal mucinous cystadenoma, another in a low-grade appendiceal mucinous neoplasm, and the third occurring in an appendiceal mucinous adenocarcinoma. The clinicopathologic characteristics of these three present cases and two previously reported cases are discussed in detail. The mechanism of heterotopic ossification in appendiceal mucinous neoplasm is still unclear, but mucin extravasation and subsequent calcification may be predisposing events.