Predictive factors for non-mass enhancement occult in conventional breast imaging: The "PAMAS" study

To identify predictive factors for malignancy in non-mass enhancement occult on conventional imaging (NMEOCI) using MRI, focusing on morphological traits and clinical contexts to refine management strategies.

This retrospective single-center study reviewed all MRI-guided biopsies performed for NMEOCI between January 2015 and October 2021 at a European oncology reference facility. Exclusion criteria were unavailability of the MRI that led to the biopsy, inability to perform control clip MRI or surgery certifying correct targeting, and clustered ring enhancement. Clinical and radiological characteristics were analyzed, and a multivariate logistic regression model assessed associations with malignancy as confirmed by pathological analysis.

One hundred and twenty-eight patients (median age, 58.0 years (Q1-Q3: 45.5-68.0), 128 women) were evaluated. Increased risk of malignancy was associated with older age (p = 0.013), preoperative context (p = 0.050), presence of homolateral neoplasia (p = 0.031), or axillary adenomegaly (p = 0.034). In contrast, MRIs performed without indications (p = 0.044) or as part of screening for high-risk patients (p = 0.033) were protective. NMEOCI features such as larger size (p < 0.001), segmental distribution (p < 0.001), and micronodular character (p < 0.001) were correlated with malignancy risk, whereas homogeneous enhancement suggested benignity (p < 0.001). Five of these characteristics were independently associated with lesions at risk of malignancy: preoperative context, age of patient, micronodular enhancement, axillary adenomegaly, and segmental distribution.

Morphological characteristics and clinical contexts of NMEOCIs on MRI are associated with malignancy risk. The mnemonic acronym "PAMAS" ("not a mass" in French) is a useful guide for this type of lesion: Preoperative context, Age, Micronodular enhancement, axillary Adenomegaly, and Segmental distribution, are independently associated with lesions at risk of malignancy.

This study enhances the precision of MRI for the analysis of NMEOCI by identifying key morphological and clinical predictors of malignancy, some of which have never been studied before, potentially reducing unnecessary biopsies, and optimizing patient management.