OBJECTIVE: To investigate the added value of extracellular volume fraction (ECV) and arterial enhancement fraction (AEF) derived from enhanced CT to conventional image and clinical features for differentiating between pleomorphic adenoma (PA) and atypical parotid adenocarcinoma (PCA) pre-operation.
METHODS: From January 2010 to October 2023, a total of 187 cases of parotid tumors were recruited, and divided into training cohort (102 PAs and 51 PCAs) and testing cohort (24 PAs and 10 atypical PCAs). Clinical and CT image features of tumor were assessed. Both enhanced CT-derived ECV and AEF were calculated. Univariate analysis identified variables with statistically significant differences between the two subgroups in the training cohort. Multivariate logistic regression analysis with the forward variable selection method was used to build four models (clinical model, clinical model+ECV, clinical model+AEF, and combined model). Diagnostic performances were evaluated using receiver operating characteristic (ROC) curve analyses. Delong\'s test compared model differences, and calibration curve and decision curve analysis (DCA) assessed calibration and clinical application.
RESULTS: Age and boundary were chosen to build clinical model, and to construct its ROC curve. Amalgamating the clinical model, ECV, and AEF to establish a combined model demonstrated superior diagnostic effectiveness compared to the clinical model in both the training and test cohorts (AUC = 0.888, 0.867). There was a significant statistical difference between the combined model and the clinical model in the training cohort (p = 0.0145).
CONCLUSIONS: ECV and AEF are helpful in differentiating PA and atypical PCA, and integrating clinical and CT image features can further improve the diagnostic performance.

BACKGROUND: Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) is an inflammatory disorder with unclear causes. Paraneoplastic etiology may be a cause. We report a case of CLIPPERS with parotid carcinoma.
METHODS: A 54-year-old man with a history of lymphoma was hospitalized with a pontocerebellar syndrome. Brain MRI revealed that the pons and cerebellum were \"peppered\" with punctate and curvilinear enhancement lesions that supported the diagnosis of CLIPPERS. The relapse of lymphoma was excluded by a further cerebellum biopsy revealing predominantly CD3+ T cells in white matter. The patient was relieved after pulse therapy with intravenous methylprednisolone and a large dose of corticosteroids, but he complained of a worsening gait problem when corticosteroids were tapered to a lower dose. Although the clinical symptoms gradually improved again by increasing the dosage of corticosteroids with Azathioprine, the patient still had a slight unsteady gait during follow-up. At the 7-month follow-up, a parotid mass was detected by MRI and was verified as carcinoma by biopsy. After resection of parotid carcinoma, the residual symptoms and previous MRI lesions disappeared, and no relapse occurred.
CONCLUSIONS: CLIPPERS may not be a distinct nosologic entity but an overlapping diagnosis with other diseases. Some cases of CLIPPERS might be a subtype of paraneoplastic neurological syndromes (PNS) due to the similar mechanism of antibody-mediated encephalitis. Tumor screening and serum paraneoplastic autoantibody tests are recommended for patients with CLIPPERS, especially for those who relapse when corticosteroids treatment is stopped or tapered.