Breast cancer, the most frequent disease amongst women worldwide, accounts for the highest cancer-related mortality rate. Triple-negative breast cancer (TNBC) subtype encompasses ~15% of all breast cancers and lack estrogen, progesterone, and HER2 receptors. Although risk factors for breast cancer are well-known, factors underpinning breast cancer onset and progression remain unknown. Recent studies suggest the plausible role of oncoviruses including human papillomaviruses (HPVs), Epstein-Barr virus (EBV), and mouse mammary tumor virus (MMTV) in breast cancer pathogenesis. However, the role of these oncoviruses in TNBC is still unclear. In the current study, we explored the status of high-risk HPVs, EBV, and MMTV in a well-defined TNBC cohort from Croatia in comparison to 16 normal/non TNBC samples (controls) using polymerase chain reaction assay. We found high-risk HPVs and EBV present in 37/70 (53%) and 25/70 (36%) of the cases, respectively. The most common HPV types are 52, 45, 31, 58 and 68. We found 16% of the samples positive for co-presence of high-risk HPVs and EBV. Moreover, our data revealed that 5/70 (7%) samples are positive for MMTV. In addition, only 2/70 (3%) samples had co-presence of HPVs, EBV, and MMTV without any significant association with the clinicopathological variables. While, 6/16 (37.5%) controls were positive for HPV (p = .4), EBV was absent in all controls (0/16, 0%) (p = .01). In addition, we did not find the co-presence of the oncoviruses in the controls (p > .05). Nevertheless, further investigations are essential to understand the underlying mechanisms of multiple-oncogenic viruses’ interaction in breast carcinogenesis, especially TNBC.

In the current study, we assessed the prevalence and molecular features of HER2-low phenotype in the apocrine carcinomas of the breast (ApoCa) and its relationship with tumor-infiltrating lymphocytes (TILs). A cohort of 64 well-characterized therapy-naïve ApoCa was used. The TIL distribution was assessed using the hematoxylin and eosin whole slide/scanned images following the international TILs working group recommendations. Next-generation sequencing (NGS) was performed in a subset of HER2-low ApoCa. All patients were women, with a mean age of 62 years. Forty-three carcinomas were pure apocrine carcinoma (PAC; ER−/AR+), and the remaining 21 were classified as apocrine-like carcinomas (ALCs; ER+/−, AR+/−). HER2/neu was positive (score 3+ by IHC and/or amplified by FISH) in 20/43 (47%) PAC and 4/21 (19%) ALC. The prevalence of HER2-low expression (scores 1+ or 2+ without HER2 amplification) in ApoCa was 39% without significant differences between PAC and ALC (P = 0.14); however, the HER2-low phenotype was more prevalent in triple-negative PAC than in ALC (P < 0.001). Levels of TILs were low (≤10%) in 74% of ApoCa (median 5%, range 0%–50%). TIL levels were significantly higher in ALC than in PAC (P = 0.02). HER2 status had no impact on TIL distribution (P = 0.45). The genomic profile of HER2-low ApoCa was similar to other subtypes of ApoCa. ApoCa has predominantly low TIL, particularly PAC. The prevalence of the HER2-low phenotype in ApoCa is high, which should have therapeutic and clinical implications given the recently approved therapies with antibody–drug conjugates (ADCs) for HER2-low breast cancers.

High infiltration by tumor-infiltrating lymphocytes (TILs) is associated with favorable prognosis in different tumor types, but the clinical significance of their spatial localization within the tumor microenvironment is debated. To address this issue, we evaluated the accumulation of intratumoral TILs (itTILs) and stromal TILs (sTILs) in samples from 97 patients with early triple-negative breast cancer (TNBC) in the center (sTIL central) and periphery (sTIL peripheral) of tumor tissues. Moreover, the presence of primary and secondary lymphoid aggregates (LAs) and the expression levels of the cancer testis antigen (CTA), NY-ESO-1, and PD-L1 were explored. High infiltration by itTILs was observed in 12/97 samples (12.3%), unrelated to age, Ki67 expression, tumor size, histologic type and grade, and LA presence. NY-ESO-1 was expressed in tumor cells in 37 samples (38%), with a trend suggesting a correlation with itTIL infiltration (p = 0.0531). PD-L1 expression was detected in immune cells in 47 samples (49%) and was correlated with histologic grade, sTILs, and LA formation. The presence of primary LAs was significantly correlated with better disease-free survival (DFS) (p = 0.027). Moreover, no tumor progression was observed during >40 months of clinical follow up in the 12 patients with high itTILs or in the 14 patients with secondary LAs. Thus, careful evaluation of lymphoid infiltrate intratumoral localization might provide important prognostic information.

Aim: Activating somatic mutations in p110α catalytic subunit of PIK3-kinase (PIK3CA) are present in about 40% of breast cancers (BC), and are involved in oncogenesis and cancer growth. PIK3CA inhibitor therapy is approved for patients with advanced H...