Pseudoangiomatous Stromal Hyperplasia

Pseudoangiomatous Stromal Hyperplasia

Some cases of PASH form firm rubbery circumscribed masses. This lesion has been bisected to show the white whorled surface of the tumor image within an area of yellow adipose tissue image.

The stromal myofibroblasts forming PASH surround normal ducts and lobules and are associated with characteristic clefts. In this case, there is a discrete mass with a circumscribed border image.



  • Pseudoangiomatous stromal hyperplasia (PASH)


  • Pseudoangiomatous hyperplasia of mammary stroma

  • Nodular myofibroblastic stromal hyperplasia

  • Nodular or tumorous PASH


  • Proliferation of myofibroblasts associated with stromal clefts that resemble vascular spaces


Possible Relation to Hormonal Milieu

  • Occurs most frequently in women of childbearing age

  • Postmenopausal women receiving hormonal therapy may also be affected

  • Similar stromal changes are often present in gynecomastia and juvenile hyperplasia

    • Thus, stromal proliferation of myofibroblasts is likely due to hormonal stimulation or hormonal imbalance

  • It has been suggested that the clefts are prelymphatic channels that drain into true lymphatics

    • Some carcinomas invade with pattern suggesting that they involve clefts seen in PASH



  • May be incidental finding in approximately 23% of biopsies

  • Also forms palpable masses or radiographic densities (nodular or tumorous PASH)

    • Masses are circumscribed or ill defined

  • PASH frequently grows in size

    • Rapid growth can occur during pregnancy and may be associated with peau d’orange and skin necrosis


Jul 6, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Pseudoangiomatous Stromal Hyperplasia

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