Fine needle aspiration cytology of mammary pseudoangiomatous stromal hyperplasia. A case report.

BACKGROUND: Pseudoangiomatous stromal hyperplasia (PASH) is an unusual benign breast lesion that may occasionally present as a palpable mass.

CASE: This report describes the fine needle aspiration cytology (FNAC) features of a case of mammary PASH that presented as a palpable mass. This is the second description of the FNAC features of this lesion and the first reported case in which a diagnosis of phyllodes tumor was considered. The aspirate was cellular and contained cohesive groups of cells in which there was a dual population of epithelial and myoepithelial cells. Occasional cellular stromal fragments were present, as were typical, bipolar, bare nuclei. Admixed with the bare nuclei were large numbers of plump, spindle-shaped cells, some with intact cytoplasm. Histologic examination of the excised mass showed features typical of PASH.

CONCLUSION: Mammary PASH may present as a palpable mass and is likely to be encountered in FNAC specimens. This diagnosis should be considered when one is confronted with an aspirate containing cohesive epithelial groups, cellular stromal fragments and large numbers of single, spindle-shaped cells. These features on FNAC may result in consideration of a phyllodes tumor. The single, spindle-shaped cells may be a characteristic cytologic feature of PASH.