The Distinct Pattern of Granulomatous Lobular Mastitis with Erythema Nodosum: More Severe Conditions and Extensive Lesions.

Purpose: Granulomatous lobular mastitis (GLM) is a benign inflammatory disease of the mammary gland with unknown etiology. Erythema nodosum (EN) is a rare, extramammary symptom of GLM. The purpose of this article was to investigate the clinical features of EN associated with GLM.

Methods: We recruited 102 GLM patients diagnosed between December 2018 and December 2021 at Renmin Hospital of Wuhan University. The clinical characteristics and laboratory indices of the EN group (n = 12) and the non-EN group (n = 90) were compared.

Results: The proportion of GLM patients with lesions involving ≥2 quadrants and high peripheral white blood cell count, absolute neutrophil count and neutrophil-to-lymphocyte ratio (NLR) was larger in the EN group than in the non-EN group (p = 0.002, 0.025, 0.014, 0.002, respectively). The duration of EN was longer in GLM patients with EN than in GLM patients without EN (p = 0.005). GLM patients with EN had more abscesses and sinus tracts than those without EN (p = 0.003, 0.038). Lesions involving ≥2 quadrants and the NLR were positively associated with the occurrence of EN (R = 0.304, 0.0302, p = 0.002, 0.002). Receiver operating characteristic curve analysis revealed that the area under the curve of the NLR was 0.770. When NLR > 5.73, the sensitivity and specificity of predicting EN were 66.67% and 87.78%, respectively.

Conclusion: Our findings suggest that GLM concomitant with EN suggests the presence of a more severe condition and extensive lesions.