Clinical History
A 40-year-old asymptomatic woman underwent a screening mammography.
Imaging Findings
Bilateral, two-view mammography (medio-lateral oblique and cranio-caudal views) was obtained. Mammograms of the right breast revealed a noncalcified, circumscribed mass in the outer quadrants with 3 cm.
Ultrasonography demonstrated a circumscribed, heterogeneous, hypoechoic solid mass (Fig. 2, 3 and 4).
A core biopsy was performed, that showed the presence of spindle cells in the fibrous tissue in a pseudoangiomatous pattern which fitted the diagnosis of pseudoangiomatous stromal hyperplasia (PASH).
Considering the size of the lesion surgery was planned, with a wire localisation because the mass was not palpable (Fig. 1).
Discussion
Pseudoangiomatous stromal hyperplasia (PASH) is a rare benign condition characterised by proliferation of the mammary stromal tissue. Histology shows slit-like spaces lined by a single layer of flat spindle cells simulating vascular spaces, within a background of stromal hyperplasia.
Although the aetiology of PASH is unknown, it is thought that it probably represents a proliferative response of myofibroblasts to hormonal stimuli [1, 2]. It typically appears in women of reproductive age [1, 2, 3].
Clinicopathologically, it may present in different forms, from incidental focal microscopic findings, to clinically and mammographically obvious breast masses.
PASH is frequently found in breast biopsy as an incidental finding. On the other hand, the tumoral form is rare and clinically evident. In about 40% of cases it presents as a palpable, unilateral and painless mass, with sizes ranging from 1cm to 15cm [2, 4].
Theses masses often increase over time and can recur after excision [4].
At mammography, PASH usually presents as a circumscribed or partially circumscribed mass, noncalcified, rarely showing irregular margins. However, in some cases it presents only as a localised increase of stroma.
The most common ultrasonographic appearance of PASH is a hypoechoic oval circumscribed mass. In some cases, echotexture may be slightly heterogeneous and rarely presenting small cystic spaces [2, 4].
Posterior sound quality ranges from mild enhancement to moderate shadowing [2].
Despite frequency of growing and recurrence, malignancy hasn't been reported and they aren't considered premaligant lesions [5].
PASH is a rare benign condition, usually diagnosed on triple assessment. After histological confirmation, regular follow-up is usually appropriate. However, in patients with large masses, surgery is indicated. Excision is also preferable when there isn't a definitive diagnosis, or even if it's the patient's choice.
After excision regular follow-up is advisable, since local recurrence can occur [1].
Differential Diagnosis List
Pseudoangiomatous stromal hyperplasia
Fibroadenoma
Hamartoma
Phyllodes tumour
Angiossarcoma
Carcinoma
Final Diagnosis
Pseudoangiomatous stromal hyperplasia
