Axillary Lymph Node Metastasis of Invasive Micropapillary Carcinoma and Invasive Carcinoma of No Special Type: A Case-control Study

  Objective  To explore the difference in clinicopathological characteristics between invasive micropapillary carcinoma (IMPC) and invasive carcinoma of no special type (NST), and analyze its association with axillary lymph node metastasis.

  Methods  The clinicopathological data of 92 IMPC cases treated within the period from August 2010 to August 2013 in Peking Union Medical College Hospital were retrospectively analyzed. From patients in the same period, 368 NST cases were randomly selected as control group. The difference in clinicopathological characteristics between IMPC and NST were compared, and the factors associated with axillary lymph node metastasis were analyzed.

  Results  There were significant differences in tumor size(2.9±1.9)cm vs. (2.1±1.4)cm, P=0.001, lymph-vascular invasion rate(85.9% vs. 6.0%, P < 0.001), axillary lymph node metastatic rate (71.7% vs. 47.3%, P < 0.001), number of involved lymph node(8.2±9.9 vs. 2.9±5.7, P < 0.001), progestogen receptor expression (P=0.047), human epidermal growth factor receptor-2 (HER-2) expression (P=0.009), Ki-67 index (P < 0.001), TNM staging (P < 0.001), and molecular subtype (P < 0.001) between IMPC and NST. The axillary lymph node metastatic rates of tumor containing ≤ 24%, 25%-49%, 50%-75% and ≥ 76% IMPC component were 73.9%, 56.3%, 72.2% and 77.1%, respectively. The axillary lymph node metastatic rate was not correlated with the percentage of IMPC component (P=0.347), but correlated with T-staging(P=0.001), HER-2 expression (P=0.029), molecular subtype (P=0.003), P53 expression(P=0.003), and Ki-67 index (P=0.045). The axillary lymph node metastasis of NST was found correlated with T-staging(P < 0.001), histological grade (P=0.001), lymph-vascular invasion (P < 0.001), estrogen receptor α expression (P=0.007), progestogen receptor expression (P=0.031), HER-2 expression (P=0.008), and molecular subtype (P < 0.001).

  Conclusions  IMPC is a distinct variant of invasive breast carcinoma with a high propensity for lymph-vascular invasion and axillary lymph node involvement. IMPC and NST have different clinicopathological characteristics. The percentage of IMPC component does not correlate with axillary lymph node metastasis. Compared with NST, there are less clinicopathological determinants for axillary lymph node metastasis in IMPC.