Periductal Mastitis, a Disease with Distinct Clinicopathological Features from Granulomatous Lobular Mastitis

Abstract

Purpose: Periductal mastitis (PDM) is a chronic inflammatory lesion of the breast with an unknown etiology, and it is difficult for clinicians to differentiate it from granulomatous lobular mastitis (GLM), although they have different treatment strategies and prognosis. This study aimed to investigate the differences in their clinicopathologic features to inform treatment strategies.

Patients and methods: Between 2011 and 2020, 121 patients diagnosed with PDM and 57 patients with GLM were retrospective analysis. Patient data were extracted on demographics, clinical presentation, pathologic characteristics, treatments and clinical response. Histopathological evaluations were performed on core needle biopsy specimens. Immunohistochemical stains using antibodies against CD3, CD4, CD8, CD20, and CD138 was performed to define immune cell infiltration.

Results: PDM patients had a higher median age compared to GLM patients (38 vs 32, p<0.001). PDM was primarily located in the areolar area, while GLM predominantly affected the peripheral quadrant of the breast (56.20% vs 75.44%, p<0.001). Histopathologically, more ductal dilatation (90.08% vs 3.51%, p<0.001), ductal wall thickening (47.93% vs 1.75%, p<0.001), and ductal rupture (44.63% vs 5.26%, p<0.001) were observed in PDM. GLM presented with significantly more granuloma (94.74% vs 10.74%, p<0.001), microabscess (68.42% vs 28.93%, p<0.001), and lipid vacuole (40.35% vs 8.26%, p<0.001) formation than PDM. Immunohistochemical analysis revealed a significant presence of CD20+ B lymphocytes in PDM and a higher prevalence of CD8+ T lymphocytes in GLM, indicating differing immune responses. Treatment outcomes varied, with PDM patients responding well to surgery and anti-mycobacterial therapy, while GLM patients showed favorable responses to steroid therapy.

Conclusion: PDM is a specific entity with a similar clinical presentation but distinct histopathological features and immune profiles to GLM. Further research is needed to elucidate the pathogenesis and optimize therapeutic approaches for these breast inflammatory conditions.

Keywords: etiology; granulomatous lobular mastitis; immunology; pathology; periductal mastitis.

Figure 1

Typical clinical manifestations of PDM and GLM. (A) Patients with periductal mastitis present with a periareolar mass with surface skin redness and nipple retraction. (B) Patients with granulomatous lobular mastitis present with a peripheral breast mass with skin redness and nipple retraction and skin ulceration. (C) Patients with severe periductal mastitis suffer from extensive abscess formation, skin ulceration, and fistula formation.

Figure 2

Pathological features of PDM and GLM. 2Ai: Disruption of the lobules of the breast with cystic dilatation of the ducts, which contain a large amount of secretions; 2Aii: Hyperplasia of fibrous tissue around dilated breast ducts with marked lymphocytic infiltration; 2Aiii: Large infiltration of foam cells in the interstitium of the breast; 2Aiv: Massive plasma cell infiltration around the dilated duct. 2Bi: Multifocal non-caseating granulomas centered on lobular units of the breast; 2Bii: The fusion of lesions has destroyed the lobular structure of the breast and microabscesses can be observed. 2Biii: Infiltration of eosinophils in the lobules of the breast; 2Biv: Lipid-dissolving vacuoles rimmed by neutrophils surrounded by lymphocytes, epithelioid cells, plasma cells.

Figure 3

Differences in the distribution proportions of CD3, CD20, and CD138 positive cells in PDM and GLM. *p=0.015, **p<0.001.

Figure 4

The difference in the distribution proportions of CD4 and CD8 positive cells in PDM and GLM.