Pseudoangiomatous Stromal Hyperplasia (PASH)

• Introduction:
  • PASH may be mistaken for mammary angiosarcoma:
    • But is not associated with an increased risk of developing:
      • Angiosarcoma
      • Invasive ductal carcinoma, or 
      • Other breast malignancies
  • There is no indication for genetic counseling or testing:
    • Based on a diagnosis of PASH
  • Excisional biopsy is not required:
    • With concordant and benign findings on mammography and core biopsy
• Pseudoangiomatous stromal hyperplasia (PASH):
  • Is a benign proliferative breast disease that was first described by Vuitch et al.
  • This lesion is characterized by:
    • A dense, collagenous proliferation of mammary stroma:
      • Forming inter-anastomosing capillary-like spaces
  • It is thought that hormonal factors play an important role in PASH:
    • According to Anderson et al:
      • This lesion represents an important hyper-response to progesterone and estrogen
  • PASH is a common histological finding in breast biopsy specimens and can also be found in a normal breast:
    • That is in association with proliferative or non-proliferative fibrocystic changes:
      • But it is rarely a symptomatic lesion
  • Clinically, PASH can presents as:
    • A solitary firm, mobile, palpable lump 
    • As multifocal nodules:
      • In 60% of cases 
    • Can be discovered incidentally on imaging
  • PASH can be found in:
    • Teenage girls as well as in postmenopausal women with or without hormonal therapy replacement
  • It is important to recognize this entity because it can be easily confused with:
    • Other benign tumors, such as:
      • Fibroadenoma
      • Phyllode tumor
    • With malignant tumors, such as:
      • Angiosarcoma
  • Unfortunately, imaging features of PASH are non-specific:
    • On mammography:
      • The most common appearance described is:
        • A well-defined, uncalcified mass, with regular borders
      • Spiculated borders, suspicious borders, and architectural distortion can also be seen:
        • But are uncommon
    • On ultrasound:
      • PASH tends to be:
        • An oval, round hypoechoic mass or 
        • Can presents as a heterogeneous mass with cystic areas 
    • According to Cohen et al:
      • When a focal lesion with well-defined borders, containing no calcifications on mammography or a well-defined hypoechoic mass on ultrasound is seen:
        • PASH can be considered and included in the differential diagnosis
  • Clinically and on imaging, the differential diagnosis include:
    • Fibroadenoma:
      • Especially in young patient
    • Phyllode tumor:
      • In older women
  • Histologically:
    • PASH can be very similar to low-grade angiosarcoma
    • Definitive diagnosis is based on histology:
      • But unlike low-grade angiosarcoma:
        • PASH has no invasive features and contains no necrosis, mitoses, and no destruction of mammary epithelial structures
  • Management of PASH depends on presentation:
    • When PASH is incidentally discovered or when it is asymptomatic:
      • It can be followed up yearly by ultrasound or mammography:
        • For a period of 36 months
    • Surgical procedures are indicated for:
      • Symptomatic lesion with mechanical complaints
      • Pain
      • Apprehension for an alternative malignant lesion 

Imaging: bilateral MLO and CC views of the breasts. There is an ovoid mass in the right lower, outer quadrant.

• References:
  • Celliers L, Wong DD, Bourke A. Pseudoangiomatous stromal hyperplasia: a study of the mammographic and sonographic features. Clin Radiol. 2010;65(2):145-149.
  • Guray M, Sahin AA. Benign breast diseases: classification, diagnosis, and management. Oncologist. 2006;11(5):435-439.
  • Hargaden GC, Yeh ED, Georgian-Smith D, Moore RH, Rafferty EA, et al. Analysis of the mammographic and sonographic features of pseudoangiomatous stromal hyperplasia. AJR Am J Roentgenol. 2008;191(2):359-363.
  • Salvador R, Lirola JL, Domínguez R, López M, Risueño N. Pseudo-angiomatous stromal hyperplasia presenting as a breast mass: imaging findings in three patients. Breast. 2004;13(5):431-435.

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