A mucocele of the appendix seen as an adnexal mass on ultrasound scan

The 'onion skin' sign of a low-grade appendiceal mucinous neoplasm: An incidental finding during early pregnancy assessment

A low-grade appendiceal mucinous neoplasm (LAMN) is a cystic dilatation of the appendix resulting from the accumulation of mucinous secretions caused by a luminal obstruction. Although usually benign, pseudomyxoma peritonei may occur in the event of rupture, and 10% of cases may be secondary to appendiceal cystadenocarcinoma. A LAMN is both more common and more likely to have a malignant association in women, making it an entity with which practitioners of gynaecological ultrasound should be familiar. Although not the primary aim, early pregnancy ultrasound assessments can offer the diagnostic opportunity to identify pelvic pathology. A LAMN can be identified on ultrasonography by visualisation of an adnexal mass separate to the ovary, which due to the layers of secretions has a distinctive appearance previously likened to 'onion-skin' or 'whipped-cream'. Here, we describe an incidental finding of a LAMN during an early pregnancy assessment. Practitioners of early pregnancy ultrasound should be familiar with the characteristic morphology of this rare but important finding.

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

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.

Nonovarian Mimics of Ovarian Malignancy

Once a pelvic mass is identified on an ultrasound examination, the first step in the differential diagnostic work up is to determine its origin. Most lateral pelvic masses in women are ovarian in origin, and the distinction between ovarian and nonovarian mimics of ovarian cancer is critical for appropriate clinical and surgical management. Adnexal masses detected on ultrasound can be further characterized by magnetic resonance imaging (MRI) when needed. Superior contrast resolution, multiplanar imaging, characteristic signal intensity of common pathology such as dermoid tumors or endometriomas allows one to accurately evaluate adnexal tumors with supplemental use of MRI. Commonly encountered extraovarian abnormalities that mimic ovarian malignancies are categorized as being either predominantly cystic or solid. The common causes of such extraovarian lesions that mimic ovarian pathology include fallopian tube diseases, paroaovarian cysts, peritoneal inclusion cysts, and a pedunculated or a broad ligament fibroid. Less common causes of cystic and solid nonovarian mimics of ovarian malignancy include mucocele of the appendix, lymphocele, spinal meningeal cysts, extraovarian endometriomas, extraovarian fibrothecomas, and gastrointestinal stromal tumors (Table 1). Identifying a normal appearing ovary is the key in distinguishing an extraovarian pelvic mass from an ovarian tumor. This becomes particularly challenging in postmenopausal women with atrophic ovaries. In this scenario, MRI comes into use by identifying small atrophic ovaries more often than ultrasound is able to. Extraovarian lesions typically displace the pelvic sidewall vasculature medially, ureters tend to be compressed, encased or medially displaced, enhancement matches pelvic arteries and may be associated with engorged mesenteric vessels compared to gonadal vessel engorgement seen with ovarian tumors.