Pseudoangiomatous stromal hyperplasia (PASH) was first described by Vuitch et al. 1 in 1986 as a benign lesion composed of a proliferation of stromal tissue with a complex pattern of interconnected spaces. Its recognition is important, since it can be confused on histologic examination with low-grade angiosarcoma and cystosarcoma phylloides. 2 Originally, this lesion was described as a distinct breast entity, but it has been seen as a component of various mammary lesions. 3 Clinical features of pseudoangiomatous stromal hyperplasia consist of a palpable, mobile, firm, painless mass. On mammography, the mass is oval to round and iso-opaque with respect to the adjacent fibroglandular breast tissue. 4 The histogenesis of pseudoangiomatous hyperplasia is still the subject of controversy. Fisher et al., 5 in 1992, suggested that PASH is a variant of breast hamartoma. Powell et al. 2 showed, however, that the cellular proliferation and the staining qualities indicate a myofibroblastic proliferation. The cytologic features of this benign lesion have been described in the literature. 6 Vicandi et al. 6 reported the cases of six patients with PASH diagnosed by fine-needle aspiration (FNA). A common cytologic feature found in five of their cases was the presence of medium to small monolayered clusters of ductal epithelium with variable amounts of single, bipolar, naked nuclei in the background. Other cytologic findings described by Vicandi et al. include fragments of acellular and/or cellular stroma, fibroadenoma-like patterns, and loosely cohesive clusters of atypical ductal epithelium mimicking malignancy.
We report an additional case of PASH in a 41-yr-old woman with a 6-mo history of a rapidly growing, mobile, firm, right-sided breast mass. A mammogram was taken, with findings suggestive of fibroadenoma. A few weeks later, the patient underwent fine-needle aspiration. The aspirate was cellular, showing large fragments of monolayered two-dimensional ductal epithelium (Fig. ). Dispersed through the smears were clusters of cohesive ductal cells (Fig. ). Scattered groups of poorly cellular stromal fragments (Fig. ) and a background showing sparse, bipolar, naked nuclei were also identified. A diagnosis of fibroadenoma was rendered. One month later the patient underwent excisional biopsy of the breast mass. The surgical specimen