The Impact of Micropapillary Component Ratio on the Prognosis of Patients With Invasive Micropapillary Breast Carcinoma

Micropapillary Breast Carcinoma: From Molecular Pathogenesis to Prognosis

Invasive micropapillary carcinoma (IMPC) of the breast is an infrequent type of breast cancer often discussed for its potency for lymphovascular invasion and difficulty in accurate imaging estimation. Micropapillary carcinomas are noted to be present as larger tumors, of higher histological grade and a notably higher percentage of disease-positive lymph nodes. Hormonal and HER-2 positivity in IMPC is also commoner when compared to other NST carcinomas. IMPC occurs either as a pure form or more often as a component of mixed Non-Specific Type (NST) carcinoma. The latest data suggest that despite having comparable survival rates to other histological subtypes of breast carcinoma, effective surgical treatment often requires extended surgical margins and vigilant preoperative axillary staging due to an increased incidence of lymph node invasion, and locoregional recurrence. Moreover, the presence of micropapillary in situ components within tumors also seems to alter tumor aggression and influence the nodal disease stage. In this review, we present an overview of the current literature of micropapillary carcinoma of the breast from biology to prognosis, focusing on biological differences and treatment.

A rare case of invasive micropapillary carcinoma of the breast

Invasive micropapillary carcinoma (IMPC) is a rare, distinct histological subtype of breast carcinoma. While micropapillary histological architecture is found in up to 2-8% of all breast cancers, pure micropapillary carcinoma is infrequent and comprises 0.9-2% of breast carcinomas. Invasive micropapillary carcinoma is emerging as an oncological and surgical challenge due to a plethora of characteristics that constitute this histological pattern - interestingly, both elusive and aggressive. We present the case of a woman presenting with IMPC, who was primarily treated with tumour and lymph node marking, followed by primary systemic therapy (PST), and consequent oncoplastic surgery with sentinel lymph node biopsy. Our case report outlines the importance of awareness of histological subtypes in breast cancer by focusing on a case report of IMPC. The breast surgeon must be aware of the lymphotropic behaviour of this subtype and the high prevalence of lymph node involvement in such patients, and therefore focus on rigorous axillary assessment. One must not forget that, despite having a more aggressive biological profile, IMPC has demonstrated no difference in survival when compared to other histological subtypes, and treatment should conform to international guidelines with an emphasis on nodal staging.

Differences in the clinicopathological characteristics of pure and mixed invasive micropapillary breast carcinomas from eastern China

Background

Invasive micropapillary carcinoma of the breast (IMPC) is a rare pathologic subtype of breast cancer. Since the differences in the pathological features of pure and mixed IMPCs are not fully understood, we aimed to investigate the difference in clinicopathological characteristics between localized pure and mixed IMPCs.

Methods

A total of 121 localized IMPC cases were included. The clinicopathological features and survival estimates of the pure IMPC and mixed IMPC groups were compared. Targeted sequencing was performed to investigate the genomic profile of paired primary breast cancer and metastatic tissue samples from two pure IMPCs and four mixed IMPCs.

Results

Overall, 48 cases were pure IMPC and 73 were mixed IMPC. The pure group had a significantly higher proportion of Luminal B compared to the mixed group (37.5% vs. 15.1%). The pure group had a similar HER2 overexpression rate (31.2% vs. 32.9%) and mean age at diagnosis (51.0 vs. 50.2 years), compared with the mixed group. The pure group had a significantly higher proportion of stage IIIC cases compared with the mixed group (38.3% vs. 17.8%). We found no significant difference in the 3-year disease-free survival (DFS) between the two groups (83.7% vs. 80.0%), but the mixed group had a better overall survival (OS) compared with the pure group [HR =0.28 (0.091-0.868), P=0.047].

Conclusions

We found that pure IMPC had a more aggressive behavior with locally advanced disease and a higher proportion of Luminal B than mixed IMPC. Mixed IMPC had a longer OS compared to pure IMPC, but there was no significant difference in the 3-year DFS between the two groups.

MRI and the pathology of breast invasive micropapillary carcinoma

Diagnosis of breast invasive micropapillary carcinoma (IMPC) before surgery is of great value for determining the optimal treatment strategy. The aim of the present study was to investigate the magnetic resonance imaging (MRI) and pathological features of IMPC. MRI features of IMPC were characterized in relation to the patients' clinicopathological features. Clinical manifestations, mammography results and/or MRI findings of patients with IMPC were retrospectively analyzed. Parameters included morphology, plain T2-weighted imaging (T2WI) signal intensity, the apparent diffusion coefficient (ADC), the internal enhancement mode, early enhancement rates and time-intensity curve (TIC) types during dynamic enhanced scanning. A total of 10 lesions were detected by MRI in eight patients, with one case having three lesions with the mean diameter of 34.44 mm. In plain T2WI scanning, the lesions appeared inhomogeneous with a moderate or high signal intensity. When the b value was 800 sec/mm², the average ADC value was 0.823±0.12×10⁻³ mm²/sec. A total of four cases exhibited mass-like enhancement, including an oval rim in one case (three lesions), irregular inhomogeneous enhancement in two cases and irregular uniform enhancement in one case. The margins were clear in one case (three lesions), irregular in two cases and spiculate in one case. Among the four cases with non-mass enhancement, the distribution was focal in two cases, linear in one case and regional in one case, and the internal enhancement mode was cluster-like in one case, heterogeneous in one case and uniform in two cases. The average early enhancement rate was 116.96±45.26%. TICs of type III were observed in all cases. In conclusion, MRI of IMPC demonstrated typical features of malignant tumors and lymphatic vessel infiltration, suggesting that MRI may exhibit guiding significance for the diagnosis and treatment planning of IMPC.

Prognosis of invasive micropapillary carcinoma compared with invasive ductal carcinoma in breast: A meta-analysis of PSM studies

BACKGROUND

Invasive micropapillary carcinoma (IMPC) is a rare histological subtype of breast cancer. The outcome of IMPC remains controversial; we conducted a meta-analysis of propensity score matching (PSM) studies to evaluate the prognostic difference between IMPC and invasive ductal carcinoma (IDC).

METHODS

We searched PubMed, EMBASE and the Cochrane library for PSM studies comparing survival data between IMPC and IDC. The summarized odds ratios (ORs) and 95% confidence interval (95% CI) are calculated by STATA software utilizing fixed-effect or random-effect models, depending on the heterogeneity of the eligible studies.

RESULTS

Eight PSM studies including 2102 IMPC patients are included in the meta-analysis. Compared with IDC, IMPC has a similar overall survival (OS) (estimated OR = 0.87, 95% CI: 0.61-1.25), but a shorter relapse free survival (RFS) (estimated OR = 1.31, 95% CI: 1.06-1.61); the shorter RFS might owe to the significantly higher loco-regional recurrence rate of IMPC (estimated OR = 3.60, 95% CI: 1.99-6.52). Funnel plots and Egger's tests are used to evaluate publication bias and the p value for OS and RFS are 0.036 and 0.564 respectively.

CONCLUSIONS

Our results demonstrate that compared with IDC, IMPC exhibits a similar, even favorite OS, but a shorter RFS; and the shorter RFS might owe to the significantly higher loco-regional recurrence rate of IMPC. These results could contribute to the individualized therapy and follow-up strategies for IMPC patients.