Comparison of the clinicopathological features of invasive ductal, invasive lobular, and mixed (invasive ductal + invasive lobular) carcinoma of the breast.

BACKGROUND: In this retrospective analysis, the clinicopathological features and pattern of metastatic spread of invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC), and mixed ductal/lobular carcinoma (MDLC), together with the type and outcome of surgical intervention, were comparatively evaluated.
METHODS: A total of 633 breast cancer patients with histopathological subtype IDC, ILC or MDLC were included in the study. The mean age was 52.6 ± 12.7 years. Follow-up period ranged between 0 and 33 (median 6.0) years. The groups were compared with respect to age, tumor size, nodal involvement, stage, hormonal therapy, multicentricity, multifocality, bilaterality, estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2)/neu, p53, and Ki67 expression, disease-free survival (DFS) and overall survival (OS) rates, and surgical approach.
RESULTS: The distribution of patients was as follows: IDC 508 (80.3 %), ILC 78 (12.3 %), MDLC 47 (7.4 %). Among the parameters evaluated, statistically significant differences were observed in mean tumor size (IDC 2.5 ± 1.98 cm, ILC 3.0 ± 1.8 cm, MDLC 3.2 ± 2.4 cm), advanced T stage (T3 + T4) at diagnosis (IDC 14.7 %, ILC 21.4 %, MDLC 25.6 %), N stage (N0 was dominant in IDC and ILC; N3 was dominant in MDLC), tumor-node-metastasis (TNM) stage (stage II was dominant in IDC and ILC; stage III was dominant in MDLC), HER2/neu expression (IDC 23.8 %, ILC 11.8 %, MDLC 21.4 %), and frequency of bone metastasis (IDC 14.3 %, ILC 17.9 %, MDLC 25.5 %).
CONCLUSIONS: MDLC-type tumors have different histopathological characteristics and are often diagnosed at advanced stage. However, their survival outcomes do not vary significantly from ILC and IDC.