Year : 2021 Month : May Volume : 10 Issue : 18 Page : 1296-1301

Determining the Unique Radiological Features of Lobular Breast Cancer on Imaging in Histopathologically Proven Cases – Our Institutional Experience

Kashifa Rahamath1, Bhawna Dev2, Venkata Sai P.M.3

1, 2, 3 Department of Radiodiagnosis, Sri Ramachandra Institute of
Higher Education and Research, Chennai, Tamil Nadu, India.

CORRESPONDING AUTHOR

Dr. Bhawna Dev, A7 & A9, Grassland Apartments, 98, Poonamalle High Road, Porur, Chennai - 600116, Tamil Nadu, India.
Email : bhawnadev@gmail.com

ABSTRACT

BACKGROUND

Lobular breast carcinomas have always been a diagnostic challenge, over the years, to the radiologist. They are one of the most commonly missed lesions on breast cancer screening checks, due to their varied presentation. We wanted to provide a concise and practical approach to characterise their morphology and presentation on mammography and ultrasound.

 

METHODS

A retrospective study was done for four years and a total of 699 patients with histopathologically proven breast cancer were chosen. Those patients with invasive lobular carcinoma (N = 56) and invasive ductal carcinoma (N = 538) were segregated and 50 cases from each group were selected randomly.

 

RESULTS

On mammography, an irregular, high-density mass was the most common presentation of both lobular (68 %) and ductal (86 %) carcinomas. Presentation as focal asymmetry (28 %) was significantly more prevalent in lobular breast carcinomas. Sonographically, an architectural distortion (30 %) and non-parallel orientation (28 %) was predominantly seen in invasive lobular carcinomas (ILCs). Mass (88 %) with micro lobulated (34 %) or angular (22 %) margins was more in favour of ductal carcinoma. Other general parameters like age at presentation, positive family history, multifocality, bilaterality, tumour size and lymph nodal involvement were not significantly different between both the groups.

 

CONCLUSIONS

A careful analysis of digital breast tomosynthesis and ultrasonography, keeping in mind all the clear differentiating features, along with experience in the field, will dramatically increase the early detection of lobular breast cancers.

 

KEY WORDS

Invasive Lobular Carcinoma (ILC), Invasive Ductal Carcinoma (IDC), X-Ray Mammography, Sono-Mammography

BACKGROUND

Breast cancer ranks second among the most common cancers worldwide and is the most common cause of mortality due to cancers. In India, it has become the most common cancer in women due to the rapid expansion of the urban population. Due to the existing diversity in culture and lifestyles, the presentation of breast cancer is very variable in India.

The common presentation of breast abnormalities includes palpable lumps in the breast, nipple discharge, incidentally detected abnormalities on routine screening mammography or chest wall / skin changes in advanced disease. The infiltrating ductal carcinoma not otherwise specified (IDC-NOS), arising from the terminal ductal lobular unit (TDLU) is by far the most common histological subtype of breast cancer detected. Next in line, the infiltrating lobular carcinoma (ILC) accounts for approximately 5 - 15 % of the cancers of the breast. The rest comprises of relatively less common histological variants.1 The incidence of lobular subtype of breast cancer has seen to be significantly increased in the last two decades, which can be attributed to the more prevalent use of post-menopausal hormone replacement therapy.2

The routinely employed imaging modalities for breast cancer screening / detection include a mammogram the gold standard, usually correlated with an ultrasound of the breast. This can be supplemented by contrast-enhanced digital mammography (CEDM), MR mammogram and PET-CT (Positron Emission Tomography-Computed Tomography) in cases necessitating further evaluation.

The limitations of x-ray mammogram include chances of missing a lesion in patients with a dense breast and the possibility of missing carcinomas of the lobular variety. The age of the patient also poses a limit for use of mammography. It has been suggested for use as a screening modality in patients aged above 35 - 40 years.3 From the histo- pathological standpoint, lobular carcinomas tend to grow in a diffuse pattern, with the tumour cells tending to invade the stroma without a strong desmoplastic reaction. These features tend to make it more difficult to be detected by physical examination as well as by mammography. The overall sensitivity of mammography in detecting lobular breast cancer ranges from around 57 % to 79 %.4

However, certain radiological features when picked up carefully can help in diagnosing these hidden cancers at an earlier stage.

In this article, we present the unique imaging features of lobular breast carcinoma as compared to the invasive ductal carcinomas (IDC) on digital mammography / 3D tomosynthesis and ultrasound.

METHODS

Approval for the study was obtained from the institutional research ethics committee. This was a retrospective study, for a duration of four years, between 2016 – 2020. During this period, the histopathology reports of a total of 699 cases who had undergone mastectomy and tru-cut biopsies of breast masses at our institution and diagnosed to have breast carcinoma were obtained. The results were categorized based on the histopathological type of breast cancer. Out of these total 699 cases, 538 were diagnosed with invasive ductal carcinoma (IDC), 56 of them had invasive lobular carcinoma (ILC), 49 had invasive ducto-lobular carcinoma and the rest had other types of carcinomas. From this subset, those patients who had not undergone any imaging investigation at our Institute were excluded.

The ducto-lobular variety was not included in the study to avoid overlapping features. A total of 50 cases each of invasive lobular and invasive ductal carcinoma were randomly selected. Their mammography and ultrasound images were studied and analyzed systematically to determine the distinct imaging features of lobular breast cancer and invasive ductal carcinomas.

 

 

Image Acquisition

The modalities for image acquisition included mammography Fujifilm Amulet 3D Tomosynthesis and Ultrasound–Toshiba Aplio 500. Image analysis was done retrospectively, after blinding of the histopathological diagnosis. Chi-square test or Fischer exact was performed and analysis was done using OpenEpi software.

3D tomosynthesis was performed with Fujifilm Amulet operated at an average of 30 kVP and 15 mAs. This included the two standard views–craniocaudal and mediolateral oblique and also additional spot-compression / magnification views were taken when needed. Ultrasound of the breasts was done with a 7 - 14 MHz transducer Toshiba APLIO 500.

Image interpretation

The previously acquired images were analyzed back by two radiologists, after blinding of the histopathological diagnosis. One of the radiologists has an experience of 10 years in breast radiology and the other has 5 years of experience in the field.

 

 

Statistical Analysis

The data entry and descriptive analysis were done using Microsoft Excel (2010). The difference between various characteristics between invasive lobular and invasive ductal carcinoma was categorical and hence chi-square test or Fisher exact were performed. A P-value of < 0.05 was considered to be statistically significant. Statistical Analysis was done using Open Epi software.5

RESULTS

Total numbers of cases diagnosed with histopathologically proven breast cancer from 2016 to 2020 were 699. Of these, 76.96 % (N = 538) were found to be infiltrating ductal carcinomas, 8.01 % (N = 56) were of the infiltrating lobular type, 7.01 % (N = 49) were infiltrating ducto-lobular type, 3.57 % (N = 25) were ductal carcinoma in situ (DCIS), 2.14 % (N = 15) were mucinous carcinomas and 2.28 % (N = 16) were invasive carcinoma with medullary features. After exclusion of those patients who had no prior imaging reports, a total of 50 patients with invasive lobular carcinoma and 50 patients with invasive ductal carcinoma were randomly chosen for the study.

The average age of incidence was comparable in both groups with no statistically significant difference (P = 0.06). It was 52.3 + / - 9.28 (mean + / - SD) years in the lobular cancer type and 55.7 + / - 8.56 (mean + / - SD) years in the ductal carcinoma type. Majority of the tumours in both groups were mostly seen in breasts with a parenchymal density B (P 0.06). Concerning other general parameters, the incidence of multifocality was more common in invasive lobular carcinomas. However, this difference was statistically insignificant (P = 0.18). Other factors like axillary lymph nodal involvement, association with a positive family history for breast cancer and bilateral involvement were not significantly different between the two groups.

 

 

Digital Mammography / 3D Tomosynthesis



The mammographic findings of invasive lobular and ductal carcinomas are summarized in Table 1. Invasive lobular carcinomas most commonly presented as an irregular, high - density mass on mammography (34 out of 50 cases - 68 %), although relatively lesser than the invasive ductal carcinoma group (43 out of 50 cases - 86 %) (Figure 3 (a, b)). This difference was found to be statistically insignificant (P = 0.06). Characteristics of the mass like shape, margins and density were separately analysed for the 34 cases in the lobular carcinoma group and 43 cases in the ductal carcinoma group. However, no statistically significant difference could be seen. Tumour presentation as architectural distortion (Figure 1 (b, d)) (P 0.08) and focal asymmetry (P < 0.01) was associated more frequently with the invasive lobular carcinomas. However, only the increased incidence of ILCs as focal asymmetry was statistically significant. These findings were conspicuous on tomosynthesis, which played an indispensable role in their diagnosis and evaluation. 3D tomosynthesis was also helpful in excluding overlapping features which could simulate a mass. In the analysis of calcifications, those with a benign morphology-round / rim / dystrophic / rod like / popcorn like calcifications were not taken into account. Calcifications which appeared suspicious–amorphous (Figure 2 (a, b, c)) / coarse heterogeneous / fine pleomorphic and fine linear branching were grouped under a common subheading 'suspicious calcifications'. Although the presence of suspicious calcifications was predominant in the ductal carcinomas, it was statistically insignificant (P = 0.2). A major number of these were of fine pleomorphic and linear branching type, in a segmental or grouped distribution. No appreciable findings on mammography / tomosynthesis were seen in 3 of the ILC cases (6 %) and one of the IDC cases (2 %). The associated findings like focal skin thickening (Figure 2 (a, b, c), 3 (a, b)) and nipple retraction (Figure 2 (a, b, c), 3 (a, b)) were comparable between both the groups, except for skin retraction (Figure 1 (d)) which was mostly seen with invasive lobular carcinomas. However, this finding had no statistically significant difference (P = 0.12).

 

 

Ultrasound




The findings on sonomammography are summarized in Table 2. One of the cases of invasive ductal carcinoma group presented with a complex cystic lesion and was excluded from the study to avoid a statistical error. On ultrasound, both the groups were commonly seen as an indistinct, hypoechoic mass, but the incidence was higher in the ductal carcinoma group. This difference was found to be statistically significant (P = 0.049) (Figure 2 (d), 3 (c, d)).