Low-Grade Appendiceal Mucinous Neoplasm (LAMN) Primarily Diagnosed as an Ovarian Mucinous Tumor

Abstract

Background: Low-grade appendiceal mucinous neoplasms (LAMN) are detected in 0.7 to 1.7% of all appendicectomies. The diagnosis can be challenging, particularly in female patients where the differential diagnosis of primary appendiceal and ovarian mucinous neoplasms is unclear. Case Presentation. A 71-year-old female was referred to our tertiary hospital with the working diagnosis of a right ovarian cystic tumor. The lesion was identified through a transvaginal ultrasound performed for vague lower abdominal pain symptoms. CT scan confirmed these findings. Intraoperatively, an appendiceal mucocele was identified and a right hemicolectomy was performed. The histopathology examination revealed a LAMN. Six months later, the patient remains disease-free. A close biannual oncological follow-up has been suggested.

Conclusion: This case underlines the difficulty in determining the origin of mucinous neoplasms of the right pelvic area. Mucocele of the appendix should be considered in the differential diagnosis of a mass in the right iliac fossa.

Figure 1

Coronal CT: located in the anatomic region of the right iliac fossa, a low-attenuation cystic lesion that measures 3.3 cm × 6.5 cm with asymmetric wall thickening (red arrow) and focal calcification (black arrow). Peritumoral ascitic fluid can be detected (white arrow).

Figure 2

Gross specimen showing the dilated appendix.

Figure 3

(a) Histopathology of low-grade mucinous neoplasm of the appendix characterized by flat mucinous epithelial proliferation replacing the mucosa and fibrosis of the wall. H/E ×400. (b) Mucin-producing columnar glandular epithelium with low-grade dysplasia H/E ×200.