Inflammatory damage to ducts in mammary dysplasia: a cause of duct obliteration.

Study of 600 cases of benign mammary dysplasia showed periductal foam-cell infiltration in 62 cases. Fibrotic obliteration of ducts was found in 24-2 per cent. of the lesions with foam-cell infiltrates. By contrast, lesions of benign mammary dysplasia lacking periductal foam-cell infiltration showed a significantly lower proportion of ductal obliteration (3-3 per cent). The differences between the proportions of lesions containing obliterated ducts was most marked in younger subjects before the age of 50 yr; thereafter the differences became very much less. On the basis of the morphological observations it is suggested that periductal mastitis with significant foam-cell infiltration may damage the ducts. Some ducts appear to become occluded by collagenous plugs, whereas others show evidence of epithelial regeneration, recanalisation and healing. These findings suggest that periductal mastitis with prominent foam-cell infiltration may be the cause of one type of fibrotic duct obliteration.