Case Report: a rare case of PASH mimicking a lactational adenoma

Abstract

Pseudoangiomatous stromal hyperplasia (PASH) is a rare, benign breast lesion that is usually discovered as an incidental finding in breast biopsies. We present a case report of a twenty three-year-old female who presented with a large central mass in the left breast 24 weeks into her pregnancy. An ultrasound-guided core biopsy was performed which was reported as a lactational adenoma and due to the significant size of the mass it was excised as a suspected giant lactational adenoma. The ultrasound appearance was of a mass with well-defined superficial and radial margins with multiple large gentle lobulations, and a thin echogenic pseudocapsule pointing towards a benign diagnosis. Multiple prominent internal vessels were visualised on doppler imaging; PASH lesions do not commonly have internal blood flow which therefore pointed away from the diagnosis in this case. It is likely the imaging features were confounded by the pregnant state. Macroscopically, the lesion consisted of a large lobulated red mass measuring 170 x 170 x 75 mm and weighing 838 g with a central area containing yellow cream-like material measuring 25 x 20 mm. Microscopically, the breast tissue showed prominent gynaecomastoid-like lobules with intervening oedematous stroma showing florid pseudoangiomatous hyperplasia. There was prominent but only patchy lactational change. PASH can often be an incidental finding and is commonly found in combination with other diagnoses. It is therefore possible for PASH to be overlooked in biopsy specimens, as in this case, and it is important to analyse the breast stroma carefully for evidence of PASH, even if the biopsy contains an alternative lesion that could account for the mass seen clinically. We feel this case highlights the potential for PASH to be overlooked in core biopsy specimens when a concurrent lesion is present and therefore not appropriately treated.