Nodular salpingitis of the isthmus is a clinicopathological entity related to what is classically referred to as interstitial adenomyosis. These two lesions are due to the same aetiopathogenic process and result from inflammatory proliferation of the tubal epithelium with formation of pseudoglandular ducts. The only difference between the two is that one is ensheathed by a fine network of mesonephric muscle fibres and the other is surrounded by a thick layer of myometrial muscle fibres. These two lesions should be grouped under the same heading: nodular salpingitis. The term adenomyosis is incorrect due to the absence of endometrial glandular ducts and stroma in these lesions. Nodular salpingitis of the isthmus should be distinguished from tubal endometriosis, which is part of the clinical expression of extrauterine endometriosis. In particular, this lesion must be distinguished from interstitial endometriosis which, for some authors, corresponds to colonisation of the tubal mucosa by endometrium and, for others, to metaplasia of the tubal mucosa.