Does Identifying Whether Pseudoangiomatous Stromal Hyperplasia (PASH) Is Focal or Diffuse on Core Biopsy Correlate With a PASH Nodule on Excision?

Aims: Pseudoangiomatous stromal hyperplasia (PASH) diagnosed on core needle biopsy is generally excised. As a consequence, PASH as an incidental finding, may lead to unnecessary excisions. This study categorized PASH in biopsies as diffuse versus focal to determine if this correlates with the presence of a mass.

Methods: In a 10-year period, 253 biopsies were identified and 159 met inclusion criteria. Of these, 47 biopsies had excisions. Biopsies and excisions were classified as diffuse, involving 2 adjacent lobules, or focal PASH in a single lobule or noncontiguous lobules. The diffuse or focal category on biopsy was correlated to the category on excision. Fibroadenomas with PASH were defined as concordant with diffuse PASH on biopsy. The category was correlated to the presence/absence of a mass determined from radiographic/clinical data for the 159 biopsies.

Results: The biopsies were classified as diffuse (105, 66%) and focal (54, 34%). A total of 67% of biopsies with focal PASH showed either focal or no PASH on excision. Diffuse PASH on biopsy, had diffuse PASH in 93% of excisions. Concordance of this classification between biopsy and excision, using a Fisher's exact test (2-tailed P value is <.0001), is statistically significant. A mass was present in 102/105 (97%) of biopsies with diffuse PASH. In biopsies with focal PASH, 78% had a mass lesion.

Conclusions: Classification of diffuse versus focal PASH on biopsy was concordant with findings on excision. We found that diffuse PASH on biopsy showed strong correlation with a mass lesion. Quantifying PASH may assist with clinical-pathologic correlation and reduce unnecessary excisions.