The 365 breast biopsies out of the total of 9125 breast biopsies performed had pathology demonstrating stromal fibrosis, yielding an incidence of 4%.
Imaging findings of the 365 biopsy-proven cases of stromal fibrosis included masses (50%), microcalcifications (36%), focal asymmetry (11%), focus of enhancement on MRI (2%), architectural distortion (1%) and non-mass-like enhancement on MRI (0.01%). 263 patients (72%) were assigned BI-RADS 4A, 47 (13%) BI-RADS 4B, 3 (1%) BI-RADS 4 and 10 (3%) BI-RADS 5 and, in 42 biopsies (12%), BI-RADS was not recorded.
As illustrated in Figure 2, of the 365 cases of stromal fibrosis on initial percutaneous breast biopsy, 25 cases (7%) were subsequently upgraded on repeat biopsy (n = 12) or surgical excision (n = 13). Of these 25 cases, 7 were upgraded to ductal carcinoma in situ (DCIS) and 18 to invasive carcinoma. Of the 25 cases that were upgraded to malignancy, 12 were upgraded based on repeat biopsy. Of these, seven were performed by stereotactic-guided vacuum-assisted biopsy, one by ultrasound-guided vacuum-assisted biopsy, one by repeat ultrasound-guided 14-G core needle biopsy within 4 weeks of the initial biopsy and one by ultrasound-guided 18-G biopsy of a suspicious axillary lymph node. In the latter case, initial biopsy of a mass revealed stromal fibrosis, which was felt to be discordant, then a repeat biopsy targeting a suspicious lymph node demonstrated invasive ductal carcinoma (IDC), and both lesion and lymph node were confirmed to be malignant at surgery. The remaining two cases were upgraded by repeat ultrasound-guided 14-G core needle biopsy, at 16 and 24 months, respectively, after initial breast biopsy owing to worsening palpable mass and suspicious MRI features, respectively.
Of the 337 patients with stromal fibrosis on percutaneous breast biopsy without upgrade, 190 (56%) patients were followed up with breast imaging, 128 (38%) for at least 2 years (range, 24-91 months; median, 49 months; and mean, 52 months), and 50 (15%) were followed for less than 2 years (range, 4-22 months; median, 12 months; and mean, 11 months). In 11 cases, benignity was proven surgically. 147 (44%) patients were lost to follow-up (Figure 2). Patients who were lost to follow-up were cross-referenced with the Regional Cancer Centre. In total, 13 of these patients who were lost to follow-up had been treated for other malignancies: 9 patients for lung cancer, 1 patient for melanoma, 2 patients for contralateral breast cancer and 1 patient for metastatic cancer of unknown primary malignancy. None of these patients presented with a diagnosis of ipsilateral breast cancer within 2 years of breast biopsy.
There were no upgrades in diagnosis to malignancy in the non-cellular fibroadenoma internal control group (Figure 3).
As illustrated in Figure 4, of the 25 cases that were upgraded to malignancy, 8 cases (32%) were concordant and 16 cases (64%) were discordant with the histopathology diagnosis of stromal fibrosis. In one case (4%), a radiology-pathology correlation was not provided. Thus, out of the 365 total cases of biopsy-proven fibroadenoma, the upgrade rate in lesions with concordant radiology-pathology correlation was 2% (8 of 365). Table 1 lists the imaging findings in cases of concordance with subsequent upgrade to malignancy.
All 16 discordant cases ultimately underwent surgical excision (Table 2). In six cases of discordance, an upgrade was made at the time of surgery. In ten cases, the upgrade occurred at repeat biopsy. Of these ten cases, eight were rebiopsied with vacuum assistance, one was biopsied with 14-G core needle and, in one case, the radiologist felt that the target may not have been biopsied and a biopsy of an axillary lymph node with 18-G core needle was performed resulting in an upgrade.
In the 25 cases of upgrade, stromal fibrosis was the sole histopathology finding in 13 biopsy specimens. The most common finding in addition to the presence of stromal fibrosis was the presence of a fragment of cyst in three cases. Other histopathology findings on biopsy are outlined in Table 3.