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OBJECTIVE. The purpose of this study was to determine whether a novel morphologic characteristic of appendiceal mucoceles at CT-focal distal appendiceal dilatation with a segment of morphologically normal appendix proximally-could predict an underlying neoplastic pathologic abnormality before surgery and histopathologic assessment. MATERIALS AND METHODS. A retrospective study was performed that assessed CT cases from 2012 through 2014. Cases showing morphologic features of a mucocele were identified and categorized into two subgroups: focal distal dilatation with a segment of normal appendix proximally and generalized appendiceal dilatation. The underlying histopathologic diagnosis for each case was assessed and categorized as neoplastic or nonneoplastic. Several additional morphologic findings were also assessed. RESULTS. Forty-nine cases with confirmed histopathologic diagnoses were identified. Of those, 20 of 23 (87.0%) cases with the finding of focal distal dilatation had an underlying neoplastic cause, whereas 14 of 26 (53.8%) cases with generalized dilatation had an underlying neoplastic cause ( p = 0.012). The findings of periappendiceal fat stranding ( p = 0.004), mural calcification ( p = 0.006), and degree of luminal dilatation ( p = 0.002) also reached statistical significance. When seen in combination with focal distal dilatation, the positive predictive value for underlying neoplasm approached or reached 100%. CONCLUSION. Our study shows that isolated focal distal appendiceal dilatation with a segment of morphologically normal appendix proximally is significantly associated with an underlying neoplastic histopathologic cause. When seen in combination with mural calcification, a diameter of more than 2 cm, and absence of periappendiceal stranding, an underlying neoplastic cause is strongly suggested.

Objective: The purpose of this study was to assess the feasibility of using CT to differentiate malignant from benign lesions in patients with pathologically confirmed appendiceal mucoceles., Materials and Methods: CT scans of 18 consecutively registered patients (11 men, seven women; age range, 21-78 years) with pathologically confirmed appendiceal mucocele were reviewed retrospectively. Patients were classified into three groups according to pathologic results: nonneoplastic mucocele (n = 3), mucinous cystadenoma (n = 10), and mucinous cystadenocarcinoma (n = 5). The nonneoplastic and mucinous cystadenoma groups were formed into a benign group, and the mucinous cystadenocarcinoma constituted the malignant group. Two experienced radiologists working in consensus assessed the shape, short diameter, density, contour, and wall thickness of the masses. The presence of calcifications, internal septations, soft-tissue thickening, periappendiceal fat stranding, intraperitoneal free fluid and pseudomyxoma peritonei were also evaluated. The CT results were compared for malignant and benign appendiceal mucoceles., Results: CT showed statistically significant differences in wall irregularity and soft-tissue thickening between malignant and benign cases (p < 0.05). Short diameter of mucoceles, attenuation of intraluminal contents, maximal wall thickness, calcifications, internal septations, periappendiceal fat stranding, intraperitoneal free fluid, and pseudomyxoma peritonei in the lesions did not differ significantly between the benign and malignant groups (p > 0.05)., Conclusion: Differentiating malignant from benign mucoceles can be difficult with CT. Irregular walls and soft-tissue thickening are features most likely to be associated with malignancy.

Objective: We discuss the case of a 58-year-old woman who presented with right lower quadrant pain and fever. CT showed a right lower quadrant inflammatory mass presumed to be an appendiceal abscess. The patient underwent open drainage of the mass but failed to return for an interval appendectomy. She returned 23 months later with a recurrent right lower quadrant inflammatory mass treated initially with percutaneous drainage followed by interval appendectomy. The final pathologic diagnosis was mucinous cystadenoma with perforation., Conclusion: Primary neoplasms of the appendix are uncommon but should be considered in the correct clinical and imaging scenario.

Objective: The purpose of this report is to describe the clinical, CT, and pathologic features of non-Hodgkin's lymphoma of the vermiform appendix., Conclusion: Non-Hodgkin's lymphoma of the appendix typically manifests with acute symptoms in patients who have no prior history of lymphoma. Most patients with the disease present clinically with signs and symptoms suggestive of acute appendicitis. On CT, lymphomatous infiltration of the appendix produces markedly diffuse mural soft-tissue thickening (range of diameters, 2.5-4.0 cm; mean diameter, 3.2 cm). The vermiform morphology of the appendix is usually maintained, and aneurysmal dilatation of the lumen is sometimes seen. Stranding of the periappendiceal fat seen on CT may represent superimposed inflammation or even direct lymphomatous extension. Coexisting abdominal lymphadenopathy is not seen in all patients. Although appendiceal lymphoma is rare, the characteristic CT appearance could lead to a preoperative diagnosis.

Objective: The preoperative diagnosis of a primary appendiceal tumor can be difficult because of its rarity and the paucity of material in the radiology literature. The purpose of this study was to describe CT findings in six patients with primary mucinous cystadenocarcinoma of the appendix., Conclusion: When CT reveals a cystic mass with enhancing wall nodularity in the expected area of the appendix, especially in older patients, the possibility of primary mucinous cystadenocarcinoma should be considered.