Low grade periductal stromal sarcoma with marked sclero-elastosis

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 inphyllodes tumours. Although the term PDSS has been usedas a synonym for phyllodes tumour,it should be betterrestricted to those lesions that appear to arise from theperiductal/perilobular stroma instead of intralobular stroma.A 84-year oldwoman 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 upperouter quadrant of her right breast. The surgicalspecimen consisted of a tumour mass with infiltrating borders,firm in consistency and whitish in colour. Histologically,the tumour mass was surprisingly composed of a diffusesclero-elastosis approximately accounting for more than 80%of the entire lesion. In some areas multiple noduleswere seen, consisting of a proliferation of spindle-shaped cellsforming cuffs around individual open tubules and ducts.Some of these nodules were coalescing and infiltrating intothe surrounding fibro-adipose tissue. Neoplastic cells exhibited a mild to moderate nuclear pleomorphism and were embeddedin a variably sclero-elastotic stroma. Mitotic activityranged from 1 up to 3 mitoses per 10 HPF. Even after ameticulous search of the whole tumour tissue, papillae orleaf-like structures typically observed in phyllodes tumourswere not observed. Based on morphological and immunohistochemicalfeatures, the diagnosis of ‘low grade PDSS with extensivesclero-elastosis’ was made. Immunohistochemically, tumour cells werepositive only to vimentin and CD34. The present case highlights the possibility that PDSScan exhibit such diffuse sclero-elastosis that the underlyingmalignant cells may be easily overlooked.