Pseudoangiomatous stromal hyperplasia causing massive unilateral breast enlargement-a case report

Pseudoangiomatous stromal hyperplasia (PASH) is an uncommon mesenchymal benign breast neoplasm. PASH may present as a rapidly growing mass in pre-menopausal women. It is important to rule out other causes of a breast lump including fibroadenoma, hamartoma, phyllodes tumour and invasive adenocarcinoma. To our knowledge this is the largest case of PASH tumour in the English literature and the first to be managed with mastectomy and immediate breast implant reconstruction.

A 45-year-old woman with a history of bilateral breast augmentation for cosmesis and no other co-morbidities, presented with gross asymmetry between her right and left breasts on 13^th December 2020. She complained about pain and the noticeable difference in clothing. She underwent triple assessment (history and examination, imaging, and biopsy). Bilateral mammograms showed the right breast had a possible mass. On ultrasound imaging there was evidence of extensive ill-defined hypoechoic changes. Core biopsies and a vacuum assisted core biopsy were taken from the mass and came back as PASH/fibrocystic change on 12^th January 2021. Surgical options were discussed, and after some consideration she decided on mastectomy and immediate implant reconstruction on 15^th March 2021. She underwent the operation on 9^th September 2021 and the specimen weight was 1.911 kg and measured 27 cm × 22.6 cm × 7.4 cm which is the largest reported PASH tumour. She made an uncomplicated recovery and was seen in clinic 4 weeks later and was happy with the cosmetic outcome. PASH can present as incidental microscopic foci in biopsies to diffuse enlargement of the breast. PASH has no specific radiological or diagnostic features, therefore is diagnosed based on histology. PASH is not associated with an increased risk of malignancy and the management is dependent on the presentation. When PASH is discovered incidentally or is asymptomatic it can be followed up with serial mammography to assess growth. If there are any suspicious features or discordance following triple assessment or symptoms such as discomfort surgical excision is indicated.

PASH should be considered as part of the differential diagnosis for rapid breast enlargement. Treatment options should be discussed early with the patient to prevent progression. For rapid breast enlargement mastectomy and immediate reconstruction should be considered and discussed with the patient.