Low-grade mucinous appendiceal neoplasm mimicking an ovarian lesion: A case report and review of literature

Abstract

Background: Appendiceal tumors are rare lesions that may not be easily differentiated from primary ovarian lesions preoperatively, despite the use of advanced diagnostic methods by experienced clinicians.

Case summary: A 59-year-old G2P2 woman, with chronic pelvic pain, underwent a pelvic ultrasound that revealed an adnexal mass measuring 58 mm × 34 mm × 36 mm, with irregular borders, heterogeneous echogenicity, no color Doppler vascularization and without acoustic shadowing. Normal ovarian tissue was visualized in contact with the lesion, and it was impossible to separate the lesion from the ovary by applying pressure with the ultrasound probe. Ascites, peritoneal metastases or other alterations were not observed. With the international ovarian tumor analysis ADNEX model, the lesion was classified as a malignant tumor (the risk of malignancy was 27.1%, corresponding to Ovarian-Adnexal Reporting Data System category 4). Magnetic resonance imaging confirmed the presence of a right adnexal mass, apparently an ovarian tumor measuring 65 mm × 35 mm, without signs of invasive or metastatic disease. During explorative laparotomy, normal morphology of the internal reproductive organs was noted. A solid mobile lesion involved the entire appendix. Appendectomy was performed. Inspection of the abdominal cavity revealed no signs of malignant dissemination. Histopathologically, the appendiceal lesion corresponded to a completely resected low-grade mucinous appendiceal neoplasm (LAMN).

Conclusion: The appropriate treatment and team of specialists who should provide health care to patients with seemingly adnexal lesions depend on the nature (benign vs malignant) and origin (gynecological vs nongynecological) of the lesion. Radiologists, gynecologists and other pelvic surgeons should be familiar with the imaging signs of LAMN whose clinical presentation is silent or nonspecific. The assistance of a consultant specializing in intestinal tumors is important support that gynecological surgeons can receive during the operation to offer the patient with intestinal pathology an optimal intervention.

Keywords: Adnexal diseases; Adnexal mass; Appendiceal neoplasm; Case report; Diagnostic imaging; Pelvic neoplasm.

Figure 1

Low-grade mucinous appendiceal neoplasm presenting as a right adnexal mass (transvaginal ultrasound).

Figure 2

Low-grade mucinous appendiceal neoplasm assumed as an adnexal neoplasm: Results of the tumor assessment using the international ovarian tumor analysis ADNEX prediction model.

Figure 3

Low-grade mucinous appendiceal neoplasm mimicking an ovarian tumor (magnetic resonance imaging presentation). The blue arrow indicates the right ovary; the orange arrow indicates the tumor apparently originating from the right ovary.

Figure 4

Low-grade mucinous appendiceal neoplasm macroscopic features (appendectomy with tumorectomy specimen).

Figure 5

Appendectomy with tumorectomy specimens (histological characteristics). A: Proximal appendiceal stump with normal histological features [Hematoxylin & eosin (H&E) staining, 20 × magnitude]; B: Low-grade mucinous appendiceal neoplasm (LAMN) (H&E staining, 40 × magnitude, blue arrow showing acellular mucin); C: LAMN (H&E staining, 100 × magnitude, orange arrow absence of high-grade epithelial dysplasia).