Low-grade appendiceal mucinous neoplasm: A case report

Abstract

BACKGROUND

Low-grade appendiceal mucinous neoplasms are papillary or flat mucinous tumors with low-grade cytologic atypia. They are the most frequent source of pseudomyxoma peritonei. They can be easily misdiagnosed, due to unspecific symptoms, with acute appendicitis, retroperitoneal tumors or adnexal mass. Cases of huge appendiceal mucinous neoplasms are even more extremely rare.

CASE SUMMARY

We report a 54-year-old patient who presented with a 10-month history of constant dull distension accompanied by nausea. A surgical procedure of total hysterectomy, bilateral adnexectomy, appendectomy, greater omentectomy and right hemicolectomy was performed as a result of the findings on ultrasound, computed tomography scan and magnetic resonance imaging. Diagnosis was made after the pathological examination, which revealed low-grade appendiceal mucinous neoplasm. The patient received hyperthermic intraperitoneal chemotherapy with cisplatin and was discharged from the hospital.

CONCLUSION

Low-grade appendiceal mucinous adenomas are rare tumors that are easily misdiagnosed, and a more thorough clinical workup is required to make a definitive diagnosis.

Key Words: Low-grade appendiceal mucinous neoplasm; Pseudomyxoma peritonei; Ovarian cystadenoma; Pathology; Surgery; Hyperthermic intraperitoneal chemotherapy; Case report

Core Tip: We report a middle-aged patient who presented with persistent, dull abdominal distension and nausea, with symptoms persisting for 10 months. Imaging studies revealed a space-occupying lesion, and the patient subsequently underwent surgical resection. Histopathological examination confirmed the diagnosis of low-grade appendiceal mucinous neoplasm. Following surgery, the patient received intraperitoneal hyperthermic chemotherapy with cisplatin and was discharged in stable condition.

INTRODUCTION

Low-grade appendiceal mucinous neoplasm (LAMN) is rare disease constituting about 1% of all colorectal malignancies. The incidence of LAMN among appendectomy specimens is reported to be 0.3%-0.7%[1]. The incidence rate of LAMN is rising. The peak age of onset of LAMN is after 50 years old, slightly higher in females than males. The symptoms are not specific. Clinically, it is often diagnosed based on abdominal pain, abdominal mass or symptoms of acute appendicitis. The most serious complication is the perforation of the appendix, which leads to peritoneal seeding and forms peritoneal pseudomyxoma. The rupture of an otherwise asymptomatic and stable LAMN can seed the peritoneal cavity with mucin and neoplastic epithelium, subsequently giving rise to pseudomyxoma peritonei (PMP).

CASE PRESENTATION

Chief complaints

A 54-year-old female complained of constant dull distension in upper quadrant abdomen accompanied with nausea for 10 months.

History of present illness

She denied any other discomforts, such as fever, vomiting, abdominal pain. She received a gastroscopy at the local hospital, which showed chronic gastritis, and was treated with vonoprazan, mosapride. However, the symptoms were progressively worsening in 2 months.

History of past illness

There was no past illness.

Personal and family history

There was no significant personal and family history.

Physical examination

At admission, physical examination noted abdominal distension, epigastric tenderness, and shifting dullness positive, while right lower quadrant tenderness, McBurney’s point tenderness, and peritonitis signs were negative.

Laboratory examinations

Labs showed carcinoembryonic antigen 19.72 ng/mL, cancer antigen (carbohydrate antigen 125) 72.05 U/mL. She underwent surgery and the pathology showed LAMN, and high-grade mucinous adenomas were present in focal areas (Figure 1).

Figure 1 Immunohistochemistry. LAMN: Low-grade appendiceal mucinous neoplasm; CK: Cytokeratin; MLH: MutL homolog; MSH: MutS homolog; PMS: Postmeiotic segregation increased; HAMN: High-grade appendiceal mucinous neoplasm.

Imaging examinations

Computed tomography scan of abdomen with contrast showed a huge multilocular cystic mass (187 mm × 117 mm × 206 mm) in the abdomen and pelvic considered ovarian cystadenoma possible, and peritoneum is thickened and blurred, peritoneal metastases needed to be excluded (Figure 2). Magnetic resonance imaging suggested a high possibility of right ovarian cystadenoma. Transvaginal gynecological ultrasound showed a huge cystic mass in the abdominal cavity classified as ovarian-adnexal reporting and data system 5 type, which was considered originating from the right ovary and having ruptured possibly (Figure 3).

Figure 2 Computed tomography scan of abdomen with contrast shows the lesion before treatment.

Figure 3 Magnetic resonance imaging shows the lesion before treatment. T2W1: T2 weighted imaging; T1W1: T1 weighted imaging; T1W1 + C: T1 weighted imaging with contrast.

FINAL DIAGNOSIS

LAMN, staged as pT4aM1c.

TREATMENT

A surgery of total hysterectomy, bilateral adnexectomy, appendectomy, greater omentectomy and right hemicolectomy were performed for diagnosis and treatment. After the surgery, she received hyperthermic intraperitoneal chemotherapy (HIPEC) with cisplatin.

OUTCOME AND FOLLOW-UP

She discharged from the hospital after HIPEC. However, a follow-up examination at the local hospital 3 months later suggested residual and recurrent tumor, and she underwent surgery again and recovered well after the operation.

DISCUSSION

Mucinous neoplasia of the appendix is a rare condition that occurs in approximately 1% of the patients undergoing appendectomy[2], or even lower[3]. LAMNs are three times more likely to affect females than males and are typically found in patients between the ages of 50-60 years. Ultrasound examinations and computed tomography scans are very useful diagnostic methods. However, the diagnostic results are often discovered during surgeries for appendicitis and other abdominal organ diseases. Appendiceal mucinous neoplasm is commonly misdiagnosed as acute appendicitis, adnexal mass and retroperitoneal tumors. While this case is in disguise of ovarian cystadenoma. And confirmed diagnosis was done by the postsurgical pathology. Low-grade mucinous neoplasm has excellent prognosis after standard appendectomy. Several factors - including T stage, appendix perforation, the presence of acellular mucin on the serosa, and surgical margin status - are identified risk factors for the development of PMP. Advanced stage low-grade mucinous neoplasm involving periappendiceal area or with nodal metastasis is treated by appendectomy with surgery such as right hemicolectomy and lymph node dissection. but perforation facilitates the intraperitoneal spread of neoplastic cells and mucin, leading to PMP[4]. PMP is a typical form of advanced LAMN. LAMN with PMP is resistant to systemic chemotherapy[5]. Therefore, in general, cytoreductive surgery and perioperative HIPEC are recommended[6-10]. Preoperative diagnosis of an underlying malignancy in a mucocele is important for patient management, but is difficult to reach by imaging studies alone.

CONCLUSION

Low-grade appendiceal mucinous adenomas are rare tumors that are easily misdiagnosed, and a more thorough clinical workup is required to make a definitive diagnosis.

ACKNOWLEDGEMENTS

We sincerely thank all the authors for their valuable contributions to this research.