Background: Approximately 45–50% of breast cancers (BCs) have a HER2 immunohistochemical score of 1+ or 2+ with negative in situ hybridization, defining the “HER2-low BC” subtype. No anti-HER2 agents are currently approved for this subgroup in Europe, where treatment is still determined by HR expression status. In this study, we investigated the prognostic significance of HER2-low status in HR+/HER2- metastatic BC (MBC) patients treated with endocrine therapy (ET) plus palbociclib as first line. Methods: We conducted a retrospective study including 252 consecutive HR+/HER2- MBC patients who received first-line ET plus palbociclib at six Italian Oncology Units between March 2016 and June 2021. The chi-square test was used to assess differences in the distribution of clinical and pathological variables between the HER-0 and HER2-low subgroups. Survival outcomes, progression-free survival (PFS) and overall survival (OS), were calculated by the Kaplan–Meier method, and the log-rank test was performed to estimate the differences between the curves. Results: A total of 165 patients were included in the analysis: 94 (57%) and 71 (43%) patients had HER2-0 and HER2-low disease, respectively. The median age at treatment start was 64 years. No correlation between patients and tumor characteristics and HER2 status was found. Median PFS (mPFS) for the entire study cohort was 20 months (95% CI, 18–25 months), while median OS (mOS) was not reached at the time of analysis. No statistically significant differences, in terms of PFS (p = 0.20) and OS (p = 0.1), were observed between HER2-low and HER2-0 subgroups. Conclusions: In our analysis, HR+ MBC patients with low HER2 expression who received first-line treatment with ET plus Palbociclib reported no statistically different survival outcomes compared to HER2-0 patients. Further prospective studies are needed to confirm the clinical role of HER2 expression level.

Non-small cell lung carcinoma harbouring epidermal growth factor receptor () mutation, usually progress after an initial response to tyrosine-kinase inhibitors (TKI). Liquid biopsy enables with a simple blood draw the accurate detection of p.T790M mutation, the most common resistance mechanism, avoiding the more invasive tissue re-biopsy. However, in a subset of cases, resistance mechanisms are more complex featuring both genetic and morphological changes. Here we report the case of a 67 years-old woman, affected by an mutated lung adenocarcinoma and treated by TKI. At disease progression, the patient developed a morphological transition to squamous cell carcinoma in association to the arising of a p.E542K mutant subclone. This case illustrates that, even in the "liquid biopsy" era, cytology can have still a role by providing an overall assessment of both morphology and genetic TKI resistance mechanisms.

Background: Basaloid squamous cell carcinoma (BSCC) is a high-grade variant of squamous cell carcinoma usually localized in the aerodigestive tract, with a poor prognosis. Surgical resection is generally recommended, even if no standard treatment has been established yet. Case Report: Here, we report the case history of a patient diagnosed with BSCC at the esophagogastric junction who was successfully treated with chemotherapy alone, leading to a durable complete response. Conclusions: The presented case illustrates the diagnostic challenges associated with BSCC of the esophagus and reports an unexpected chemosensitivity of this histotype to the combination of a platinum salt plus 5-fluorouracil, which could represent an optimal treatment strategy in unfit patients.

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