Low grade periductal stromal sarcoma (PDSS) is a rare biphasic lesion characterised by a neoplastic spindle cell proliferation localised around mammary ducts/tubules that retain open lumens in absence of leaf-like processes typically seen in phyllodes tumours. Although the term PDSS has been used as a synonym for phyllodes tumour,it should be better restricted to those lesions that appear to arise from the periductal/perilobular stroma instead of intralobular stroma.A 84-year old woman presented a slightly painful right breast lesion. Mammography revealed an infiltrative, poorly circumscribed tumour mass with calcifications, measuring 2 cm in its greatest diameter, located in the upper outer quadrant of her right breast. The surgical specimen consisted of a tumour mass with infiltrating borders, firm in consistency and whitish in colour. Histologically, the tumour mass was surprisingly composed of a diffuse sclero-elastosis approximately accounting for more than 80% of the entire lesion. In some areas multiple nodules were seen, consisting of a proliferation of spindle-shaped cells forming cuffs around individual open tubules and ducts.Some of these nodules were coalescing and infiltrating into the surrounding fibro-adipose tissue. Neoplastic cells exhibited a mild to moderate nuclear pleomorphism and were embedded in a variably sclero-elastotic stroma. Mitotic activity ranged from 1 up to 3 mitoses per 10 HPF. Even after a meticulous search of the whole tumour tissue, papillae or leaf-like structures typically observed in phyllodes tumours were not observed. Based on morphological and immunohistochemical features, the diagnosis of ‘low grade PDSS with extensive sclero-elastosis’ was made. Immunohistochemically, tumour cells were positive only to vimentin and CD34. The present case highlights the possibility that PDSS can exhibit such diffuse sclero-elastosis that the underlying malignant cells may be easily overlooked.