Diagnostic challenge of a pelvic cystic mass: localized pseudomyxoma peritonei secondary to a ruptured low-grade appendiceal mucinous neoplasm

¹Radiology Department, Ar-Razi Hospital, University Hospital Center Mohammed VI, Marrakech, Morocco, ²Faculty of Medicine and Pharmacy of Marrakech, Cadi Ayyad University, Marrakech, Morocco

^&Corresponding author
Salim Ben Souayah, Radiology Department, Ar-Razi Hospital, University Hospital Center Mohammed VI, Marrakech, Morocco

Introduction    

Pseudomyxoma peritonei (PMP) is a rare clinicopathological condition characterized by progressive accumulation of mucinous ascites associated with dissemination of mucin-producing epithelial cells within the peritoneal cavity [1]. In most cases, it originates from the rupture of a low-grade appendiceal mucinous neoplasm (LAMN), whereas primary mucinous tumors arising from other organs are uncommon [1].

Because of its nonspecific clinical presentation and variable imaging findings, PMP remains a diagnostic challenge. Patients commonly present with chronic abdominal pain, abdominal distension or, less frequently, bowel obstruction, while the diagnosis is often established only after surgery and histopathological examination [1,2]. Early recognition is important because it helps guide appropriate surgical management [1].

Contrast-enhanced computed tomography (CT) is the imaging modality of choice for the initial evaluation of PMP, whereas magnetic resonance imaging (MRI) provides complementary information, particularly for characterizing indeterminate pelvic lesions and assessing their relationship with adjacent organs [2,3]. However, determining the exact origin of a mucinous pelvic mass may remain difficult when the appendix and the right ovary cannot be clearly distinguished on imaging. In such cases, histopathological examination remains essential for establishing the final diagnosis [4].

We report the case of an elderly woman with localized PMP secondary to a ruptured LAMN that initially presented as a pelvic cystic mass of uncertain origin. This case highlights the diagnostic challenge of distinguishing an appendiceal mucinous neoplasm from an ovarian mucinous tumor and emphasizes the complementary roles of CT, MRI, and histopathological examination in establishing the final diagnosis.

Patient and observation     

Patient information: 86-year-old woman, gravida 8 para 8, with a history of hypertension complicated by hypertensive heart disease treated with antiplatelet therapy and dyslipidemia treated with statins, with no previous abdominal surgery.

Clinical findings: the patient presented with a six-month history of progressive abdominal and pelvic pain, predominantly in the hypogastric region, associated with asthenia, anorexia, and weight loss. On admission, she was hemodynamically stable. Abdominal examination revealed a soft abdomen with tenderness over the hypogastric region and both iliac fossae. No palpable abdominal mass, hernia, or peripheral lymphadenopathy was noted. The remainder of the physical examination was unremarkable.

Timeline of current episode: 6 months before admission, the patient developed progressive diffuse abdominal pain, predominantly in the hypogastric region, associated with asthenia, anorexia, and weight loss. At admission, clinical examination, laboratory investigations and contrast-enhanced CT were performed. Later on, pelvic MRI was requested for further characterization of the lesion. The patient then underwent cytoreductive surgery including peritonectomy, right hemicolectomy and right adnexectomy. Histopathological examination confirmed a ruptured low-grade appendiceal mucinous neoplasm complicated by localized pseudomyxoma peritonei. At the last follow-up visit, the patient reported marked improvement in abdominal pain despite mild persistent abdominal discomfort. She was subsequently lost to follow-up, and no postoperative imaging was available.

Diagnostic assessment: laboratory investigations revealed elevated serum CA-125 (56.20 U/mL) and CA 19-9 (43.59 U/mL). Contrast-enhanced computed tomography (CT) demonstrated a predominantly cystic right latero-uterine pelvic mass closely related to the uterus and ileocecal region, without clear visualization of either the appendix or the right ovary (Figure 1). Two additional cystic lesions involving the liver and pancreas showed imaging characteristics similar to the pelvic lesion and were considered suspicious for possible secondary involvement (Figure 2).

Pelvic magnetic resonance imaging confirmed a predominantly cystic right pelvic mass containing thin internal vegetations (Figure 3). However, the origin of the lesion remained uncertain because neither the appendix nor the right ovary could be identified separately. Magnetic resonance imaging also showed diffuse endometrial thickening suggestive of endometrial hyperplasia. Based on the imaging findings, the main differential diagnoses included an appendiceal mucinous neoplasm and a primary ovarian mucinous tumor.

Diagnosis: the patient underwent cytoreductive surgery including peritonectomy, right hemicolectomy, and right adnexectomy (Figure 4 and Figure 5). Histopathological examination confirmed a ruptured low-grade appendiceal mucinous neoplasm complicated by localized pseudomyxoma peritonei. The right ovary and fallopian tube were free of tumor involvement, confirming the appendiceal origin of the disease (Figure 6).

Therapeutic interventions: considering the intraoperative findings, cytoreductive surgery consisting of peritonectomy, right hemicolectomy, and right adnexectomy was performed. Hyperthermic intraperitoneal chemotherapy (HIPEC) was not performed because it was unavailable at our institution.

Follow-up and outcome of interventions: the postoperative course was uneventful. At the last follow-up visit, the patient reported a marked improvement in abdominal pain, although mild abdominal discomfort persisted. No postoperative complications were observed. The patient was subsequently lost to follow-up; therefore, no postoperative imaging or long-term clinical outcome was available.

Patient perspective: "since the operation, my abdominal pain has significantly improved. Although I still have mild discomfort, I feel much better than before surgery, and I am overall satisfied with the treatment I received."

Informed consent: written informed consent for publication of this case report and the accompanying images was obtained from the patient's legal caregivers.

Discussion     

Pseudomyxoma peritonei (PMP) is a rare clinicopathological condition characterized by progressive accumulation of mucinous ascites associated with dissemination of mucin-producing epithelial cells within the peritoneal cavity. In most cases, it originates from a ruptured low-grade appendiceal mucinous neoplasm (LAMN), whereas other primary sites are uncommon [1,2].

Preoperative diagnosis remains challenging because both the clinical presentation and imaging findings are often nonspecific. In women, differentiating an appendiceal mucinous neoplasm from a primary ovarian mucinous tumor may be particularly difficult when the appendix and ovary cannot be clearly identified separately, as illustrated in our patient. This distinction is clinically important because ovarian involvement is frequently secondary to an appendiceal primary tumor rather than a primary ovarian neoplasm [3,4].

Contrast-enhanced CT is considered the imaging modality of choice for the initial evaluation of PMP because it accurately demonstrates the primary lesion, the extent of peritoneal disease, mucinous ascites, peritoneal implants, and scalloping of the visceral surfaces [3,5]. Magnetic resonance imaging provides complementary information, particularly for characterizing indeterminate pelvic lesions because of its superior soft-tissue contrast [3]. The imaging appearance of appendiceal mucoceles has been well described, although identifying the exact site of origin may remain difficult when adjacent pelvic organs are closely related [6]. Despite the combined use of CT and MRI, the origin of the pelvic mass could not be confidently established before surgery in our patient. Another noteworthy finding was the presence of pancreatic and hepatic cystic lesions showing imaging characteristics similar to those of the pelvic lesion. Although these findings raised the possibility of secondary involvement, their exact nature remains uncertain because neither histopathological confirmation nor postoperative imaging follow-up was available. They should therefore be interpreted cautiously [1].

Histopathological examination remains the gold standard for confirming the diagnosis and determining the primary site of disease [7]. In our case, examination of the surgical specimen confirmed a ruptured LAMN complicated by localized PMP, while the right ovary and fallopian tube were free of tumor involvement, confirming the appendiceal origin. The current PSOGI consensus has standardized the pathological classification and reporting of appendiceal mucinous neoplasms and PMP, improving diagnostic consistency and communication between pathologists and clinicians [8].

Complete cytoreductive surgery remains the cornerstone of treatment for PMP. In specialized centers, it is usually combined with hyperthermic intraperitoneal chemotherapy (HIPEC), which has been associated with improved long-term disease control in selected patients [9]. However, HIPEC was unavailable at our institution, and the patient therefore underwent cytoreductive surgery alone. Our case highlights the diagnostic challenge of determining the origin of a cystic pelvic mass when the appendix and ovary cannot be clearly distinguished on imaging. It also emphasizes the complementary roles of CT, MRI, surgery and histopathological examination in establishing the final diagnosis. Appendiceal mucinous neoplasms should therefore be considered in the differential diagnosis of complex cystic pelvic lesions, particularly in elderly women.

Conclusion     

Pseudomyxoma peritonei should be considered in the differential diagnosis of cystic pelvic masses, particularly when the appendix cannot be clearly distinguished from the ovary on imaging. Although CT and MRI play a key role in preoperative assessment, histopathological examination remains essential for confirming the diagnosis and identifying the primary site.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

All the authors have read and approved the final version of this manuscript.

Figures     

Figure 1: A, B) abdomino-pelvic CECT showing a lateral right uterine mass in close contact with the uterus

Figure 2: A,B) abdomino-pelvic CECT - cystic lesion shown in the pancreatic body and segment II of the liver

Figure 3: A-E) MRI sequences showing a right pelvic mass, predominantly cystic, with thin sparse vegetations

Figure 4: intra-operative image showing the tumour mass attached to the appendix

Figure 5: image of the surgical specimen of the hemicolectomy and right anexectomy

Figure 6: histopathological features of ruptured low-grade appendiceal mucinous neoplasm; A) cystic component; B) appendiceal perforation site (asterisk); HES staining, x200

References