Evaluation of T2 weighted hyperintense lesions on breast MRI: Imaging characteristics and histopathology correlation

INTRODUCTION

Differential diagnosis of the breast masses on contrast-enhanced MR imaging is based on the morphology, the comparative signal intensity of the lesions on T2WI (T2-weighted images), T1WI (T1-weighted images), and dynamic contrast fat sat T1W images. T2W hyperintense signal intensity lesions are brighter than the normal parenchyma. These can include benign, malignant, infectious, or inflammatory pathologies. Characterization of the lesion on T2WI, along with pre-contrast fat-suppressed T1WI and a dynamic post-contrast study helps to improve diagnostic accuracy on imaging. Various abbreviated MRI protocols use only pre-contrast T1WI and 3 dynamic post-contrast sequences.^[1] There were a few other studies that have included T2WI in their evaluation. T2W hyperintensity can be due to cyst/fluid content, microcystic component, myxoid or mucinous stroma, necrosis, hemorrhage, or edema.^[2] Fat and fluid both appear bright on T2WI, and it is essential to differentiate both components in the lesion. Where fat suppression (FS) sequence helps to differentiate the two; non-FS T2WI provides better information about morphology and architectural distortion. In breast tissue, edema can be due to trauma, hemorrhage, inflammation, infective pathologies, post-radiation changes, or lymphatic congestion. Various benign and malignant breast pathologies can demonstrate variable patterns of the MR imaging spectrum.^[3] A T2-weighted sequence before dynamic contrast-enhanced MRI is useful in the characterization of breast lesions.^[4,5] Inflammation associated with necrosis may also lead to stromal edema; tumor necrosis and perilesional edema are usually seen in high-grade cancers and demonstrate hyperintense signals on T2WI.^[6] Tumor necrosis demonstrate hyperintense signal intensity on T2WI; however, fat necrosis may present hypointense signals within the fatty island sign. On the other hand, mucinous carcinoma consists of a large amount of epithelial mucin, which is hyperintense on T2WI.^[7] Careful analysis of T2W imaging patterns of the lesions is useful to narrow the differential diagnosis and reduce false positive cases. In this study, we retrospectively analyzed imaging characteristics of various benign and malignant T2 hyperintense lesions and correlated them with histopathology findings to highlight the potential use of this particular sequence.

MATERIALS AND METHODS

It is an observational study performed in a tertiary care university hospital. It was approved by the institutional ethics committee. Dynamic contrast-enhanced MRI of breast studies of a total 144 cases were retrieved from PACS and analyzed. MRI of the breast were performed above 18 years of age on a 3 Tesla MRI scanner (MAGNETOM Vida, Siemens Healthcare, Germany) using a dedicated 18-channel breast coil. MRI examination were performed in the prone position. A multiplaner localizer with a field of view (FOV) of 300–360 mm and 3 mm of slice thickness was applied. Sequences were used; pre-contrast T2WI (TR/TE 3000/71 ms), STIR (TR/TE 3800/70 ms), DWI imaging (TR/TE 6800/70 ms), and fat-suppressed T1WI (TR/TE 6.13/3.30 ms), followed by dynamic post-contrast fat-suppressed T1WI, were obtained in 0.8 mm slice thickness in 3-D transverse orientation with TR/TE of 4.54/1.73 ms. Multihance 0.1 mmol/kg body weight was injected with a pressure injector with a flow rate of 2.0 ml/s, followed by a flush of 20 ml of saline. Amongst these patients, 107 T2 hyperintense lesions were included for the study, and 37 hypointense lesions were excluded [Figure 1]. Each lesion was analyzed for characterization on STIR, non-FS T2WI, T1WI, and FS T1-Weighted dynamic post-contrast MR images. These findings were noted in the form of signal intensity, shape, margins, and kinetic patterns. Findings were correlated with histopathology findings, and the MRI features were analyzed in various benign and malignant lesions.

Close

Figure 1:

Study analyzed 107 mass lesions which showed hyperintense signal intensity on T2WI. 80.4% were benign and 19.6% were malignant lesions. 37 hypointense mass lesions were excluded.

Export to PPT

RESULTS

Out of 107 hyperintense mass lesions, 80.4% (n = 86) were benign and 19.6% (n = 21) were malignant. [Figure 1]. Age range was 18–70 years (mean = 40.8). The most common benign pathology was fibroadenoma, found in 33.7% (n = 29) [Figure 2], followed by a cyst 20.9% (n = 18) and infection or abscess in 18.6% (n = 16) of cases. Intraductal papilloma was found in 7 (8.14%), [Figure 3] and benign phyllodes were observed in 5 (5.81%) cases [Figure 4]. Most common malignant pathology was invasive ductal carcinoma, 42.8% (n = 9) [Figure 5], followed by papillary carcinoma, 19% (n = 4), and mucinous cancer, 14.2% (n = 3) [Figure 6]. Two cases of lobular cancer and three malignant phyllodes also showed hyperintense signals on T2WI [Table 1]. The most common shape was irregular, which was present in 47.6% (n = 51) of cases (34 benign and 17 malignant), followed by oval shape. 39.2% (n = 42) (39 benign and 3 malignant) and 13% (n = 14) were round (13 benign and 1 malignant). Circumscribed margins were seen in 72 masses [69 benign, (80%) and 3 malignant, (14%)] followed by irregular in 23 [17 benign, (19%) and 7 malignant, (33%)]. Spiculated margins were observed in 52.4% (n = 11) of malignant masses [Table 2]. Perilesional edema and tumor necrosis were seen in 12 malignant lesions (57%). In dynamic contrast-enhanced study, 54.21% (n = 58) demonstrated a type I curve, 32.71% (n = 35) a type II, and 13.08% (n = 14) a type III kinetic curve. Twelve of the malignant lesions showed a type III curve (57%), and five showed a type II curve. Most of the benign lesions (58/86, 67%) showed a type I curve. Lesion characteristics on MRI have been elaborated in Table 3.

Close

Figure 2:

MRI of fibroadenoma. (a) Axial Fat sat T2WI revealed a well defined, oval hyperintense mass in left breast (blue arrow), (b) Fat-suppressed axial DCE-MRI revealed persistent homogeneous enhancement (blue arrow), (c) Proliferating glandular elements (wide blue arrow) showing mixed growth pattern. The glands are bilayered with fibromyxoid stroma (narrow blue arrow). (Hematoxylin and eosin, x400). DCE-MRI: Dynamic Contrast-Enhanced Magnetic Resonance Imaging.

Export to PPT

Close

Figure 3:

Case of intraductal papilloma. (a) Axial Short tau inversion recovery T2WI of left breast showing an oval complex cystic mass (blue arrow) with an irregular mass from lateral wall (white arrow) and few hypointense septations. (b) Well-formed fibrovascular fronds (wide blue arrow), (H and E, x100) and presence of two cell types: epithelial and myoepithelial within the papillae (narrow blue arrow) (inset: H and E, x400). H and E: Hematoxylin and eosin.

Export to PPT

Close

Figure 4:

MRI in phyllodes. (a) T2 Short tau inversion recovery Axial MRI of breast revealed an irregular mass with hyperintense cystic component (blue arrow) and hypointense internal septae (white arrow), (b) Post contrast MRI showed heterogeneous enhancement with non enhancing hypointense septae (white arrow) and cystic areas (blue arrow), (c) Benign phyllodes tumor; leaf like architecture with biphasic hyperplastic epithelium (wide blue arrow) and variable stromal cellularity (narrow blue arrow) (Hematoxylin and eosin, x100). MRI: Magnetic resonance imaging.

Export to PPT

Close

Figure 5:

Case of infiltrating ductal carcinoma. (a) Axial Short tau inversion recovery T2WI showing mass in left breast showing hyperintense signals (blue arrow) and hyperintense perlesional edema (white arrow). (b) Axial dynamic contrast enhanced MRI fat sat subtracted image showing heterogeneous contrast enhancement with early wash out (blue arrow), (c) Histopathology of infiltrating ductal carcinoma not otherwise specified (NOS); infiltrating nests and trabeculae of malignant duct epithelial cells (blue arrow), (Hematoxylin and eosin, x100; inset x400). MRI: Magnetic resonance imaging.

Export to PPT

Close

Figure 6:

Case of mucinous carcinoma. (a) Axial Short tau inversion recovery T2WI magnetic resonance imaging (MRI) of right breast revealed an oval mass with homogeneous hyperintense signal intensity and circumscribed margins (blue arrow). (b) Axial fat sat T1WI MRI showing mixed signals with hyperintense rim (blue arrow). (c and d) Histopathology showing clusters of tumor cells (wide blue arrow) surrounded by mucin (narrow blue arrow) (Hematoxylin and Eosin; x100, x400).

Export to PPT

DISCUSSION

Various benign and malignant lesions may demonstrate hyperintense signal intensity on T2WI. Pathology features that may demonstrate high signal intensity on T2WI are tumor necrosis, cystic components, mucinous or myxoid stroma, sebaceous or adipose contents, parenchymal edema, or hemorrhagic contents. Understanding the correlation between the MRI findings in specific pathological processes helps radiologists improve diagnostic accuracy.^[2]

The most common breast malignancy includes invasive ductal carcinomas, which usually present as hypointense masses on T2WI with irregular or spiculated margins and heterogeneous enhancement on post-contrast sequence. Central necrosis may present in high-grade cancers and in large masses that appear T2 hyperintense. Tumor necrosis, histologically consisting of dead and degraded tumor cells and central infarcted tissue, accumulates as fluid and debris, which demonstrates T2WI hyperintense signal intensity. Analysis of tumor necrosis is important, as the presence of tumor necrosis is associated with poor prognosis.^[6,8,9] Mucinous, invasive papillary, and metaplastic cancers are hyperintense on T2WI, as documented in various studies.^[7,10–13] In the present study also, T2 hyperintense masses included mucinous and papillary carcinomas. Histologically mucinous carcinomas are of two types: pure and mixed. On MRI they are round, oval, or lobular in shape and demonstrate circumscribed margins.^[2,6] They show very high signal intensity on T2WI and variable signals on T1WI. On post-contrast study, most of the pure mucinous cancers demonstrate slow progressive enhancement; however, in mixed mucinous cancers, it may show heterogeneous enhancement with a variable kinetic pattern.^[7] High-grade necrotic tumors show heterogeneous enhancement with a peripheral rim and early washout, type III kinetic curve.^[6,8] In present study eight invasive ductal cancers and two invasive lobular cancers also showed T2 hyperintense tumor necrosis and perilesional edema.

The differential diagnosis amongst benign T2 hyperintense lesions includes cysts, which are amongst the most prevalent findings on breast imaging. Simple cysts do not show enhancement in post-contrast studies.^[14] In our study, cysts demonstrated circumscribed margins and high signal intensities on T2WI but no enhancement, and abscesses showed peripheral rim enhancement and perilesional edema. Infected cysts showed peripheral rim enhancement, better seen on subtracted images. On histopathology cysts are fluid-filled spaces with epithelial linings. Infected cysts may contain inflammatory infiltrates, lymphocytes, and macrophages. Fat necrosis revealed hyperintense signal intensity on non-fat-suppressed T1WI and T2WI; on fat-suppressed T1WI and T2WI imaging, it shows similar signal intensity of adjacent fatty parenchyma. In the acute phase, it may show internal or peripheral post-contrast enhancement, but it reduces as development of fibrosis occurs.

Fibroadenomas are usually well-defined oval or round masses with circumscribed or lobulated margins. Due to glandular and stromal elements, these lesions show hyperintense signals on T2WI and iso- to hypointense on T1WI; hypointense septae may also be present within. In our study most of the fibroadenomas (21 out of 29) showed circumscribed margins. On histopathology, fibroadenomas are firm, well-circumscribed biphasic tumors with proliferation of both glandular and stromal elements. Glandular elements have retained the myoepithelial layer. The stromal component is generally of uniform cellularity and comprises collagen, bland spindle-shaped stromal cells with ovoid elongated nuclei, and no or rare mitotic activity observed.^[15,16] The typical phyllodes tumor is round, relatively well circumscribed, and firm. On histopathology, phyllodes tumors are solid, grey-white, whorled, bosselated, and show a leaf-like pattern; they are biphasic tumors with stromal hypercellularity and benign glandular elements. These are graded into benign, borderline, and malignant depending on stromal atypia, stromal cellularity, stromal overgrowth, mitotic count, tumor border, and malignant heterologous elements. Cystic degeneration, hemorrhage, stromal hyalinization, and myxoid changes reported in phyllodes may lead to T2 hyperintensity.^[16,17] The present study included 5 benign and 3 malignant phyllodes cases, and all of them showed hyperintense signal intensities on T2WI due to cystic and myxoid changes. Duman et al. observed that fibroadenomas are more ovoid in shape and phyllodes more frequently irregular in shape.^[18] Internal cystic areas were seen in all the phyllodes cases.^[18] In our study also all phyllodes cases showed irregular margins, septations, clefts, and cystic areas.

Intraductal papillomas are well-circumscribed polypoidal nodules that rarely exceed 3 cm in diameter. They are usually located in a cystically dilated duct. On MRI these lesions demonstrated complex solid cystic lesions in our study. Cystic areas and duct dilatations are hyperintense on T2W images; solid masses showed enhancement on post-contrast sequences. On histopathology, peripheral intraductal papillomas are not grossly visible. On microscopy, papillomas are complex and cellular and comprised of arborizing fibrovascular cores lined by an outer layer of luminal cells and an inner layer of myoepithelial cells.^[15–17]

Although this study could provide a correlation between the benign and malignant T2 hyperintense lesions, it was limited due to the small sample size and a single-center study.

CONCLUSION

T2WI hyperintensity may indicate edema, cysts, fat, fluid collection, hemorrhage, and tumor necrosis in the breast lesions. Usually malignant masses are hypointense on T2WI; however, a few malignancies, like mucinous cancers and tumor necrosis in high-grade tumors, may show hyperintense signal intensity on T2WI. Understanding the MRI characteristics on various sequences and pathogenesis can improve diagnostic accuracy in clinical practice. T2-weighted imaging sequence should be included in the abbreviated MRI protocol for characterization of the suspicious masses.