Although TNBC accounts for a fairly little minority of breast cancer cases, it is responsible for a quite large share of breast cancer deaths, due to the commonly aggressive clinical course and the lack of successful targeted therapies [7, 12].
Triple-negative phenotype is characterized by distinct clinical, histopathological, and molecular characteristics, and is associated with the development of recurrence, distant metastases, and a poorer prognosis; therefore, better understanding of the imaging features of TN cancers, especially at MRI, provides an imaging biomarker with clinical implications.
This study aimed to determine the dynamic contrast-enhanced magnetic resonance imaging features of TN breast cancers in addition to MRI features that are more frequent with triple-negative breast cancer subtypes such as round shape mass lesion, mass with rim enhancement in post contrast images, and intratumoral bright signal intensity on T2-weighted images, while still maintaining other DCE-MRI parameters commonly seen with other breast cancer subtypes as distribution of fibroglandular tissue (FGT) and BPE, mass margin, non-mass enhancement distribution and enhancement pattern, lymph nodes status, and types of kinetic curves.
In this study, the patients’ age ranged from 24 to 60 years (mean age 44.04 ± SD) which agrees with Li and Han [9] as well as Schmadeka et al. [13] who stated that TNBC more commonly affects youthful patients (< 50 years).
Similar to previous reports as Reis-Filho and Tutt [14], Sung et al. [4], Schmadeka et al. [13], and Abramson et al. [15], our study results showed that TNBCs in 80% cases were invasive ductal carcinoma.
In our study, 12/100 (12%) had almost entirely fatty breast density, 56/100 (56%) had scattered fibroglandular tissue, 32/100 (32%) had heterogeneous fibroglandular tissue, no cases (0/100, 0%) had extreme fibroglandular tissue which is in opposition to Boisserie-Lacroix et al. [7] who reported that TNBC patients are usually young and have dense breasts as well as Kim et al. [16] who reported that women with high mammographic breast density (MBD) were less likely to have triple-negative breast cancer.
104/172 (60.5%) of our cases presented as mass lesions. This goes in concordance with Dogan et al. [17], Li and Han [9], and Osman et al. [5] who stated that TNBC most often presents as mass enhancement.
As regards the shape of mass lesions in this study, 40/104 (38.5%) were rounded or oval in shape and 64/104 (61.5%) were irregular in shape; however, Sung et al. [4] found that the majority of TNBC lesions were lobulated and Ivanac et al. [18] as well as Osman et al. [5] found most TNBC were rounded and or oval masses.
We found that most masses had irregular or speculated margins (72/104, 69.2%) while 32/104 (30.8%) had smooth (circumscribed) margins compared to those of Uematsu et al. [19] whose findings which showed that 39% of the TNBCs had smooth margins. On the other hand, Youk et al. [6] and Osman et al. [5] reported that a smooth mass margin tended to be prominently associated with TNBC.
Rim internal enhancement was predominant in TNBC mass lesions (48/104, 46.2%) in this study with 24/104 (23.1%) homogenous enhancement and 32/104 (30.8%) heterogeneous enhancement. Our results are consistent with many studies [5,6,7, 16, 19, 20]. Teifke et al. [20] declared that rim enhancement is the most useful MR feature for identifying TNBC and rim enhancement is associated with higher grade tumors.
The majority of TNBC mass lesions demonstrated areas of high T2 intratumoral signal intensity (108/172, 62.8%). Our result is compatible with Sung et al. [4] and Osman et al. [5] who stated that high T2 signal intensity was significantly associated with TN cancer and that intratumoral high signal intensity on unenhanced fat suppressed T2-weighted images corresponded morphologically and pathologically to intratumoral necrosis.
Most of the patients in this study showed malignant pattern kinetic curves (types II and III), (87/104, 83.3%) This result is similar to many studies as Chen et al. [21], Dogan et al. [17], and Youk et al. [6] and unlike Uematsu et al. [19] that reported a persistent enhancement pattern was significantly associated with TNBC.
In this study, TNBC were diagnosed by DCE-MRI in all cases, and this coincides with previous studies such as Dogan et al. [17] who studied the characteristics of TNBC by mammography, ultrasound, and MR imaging; TNBC were detected by MRI in all cases and in 91% and 93% of cases by mammography and ultrasound, respectively. Also, Schmadeka et al. [13] suggested that MRI is the most sensitive (99–100%).
