# Evaluation of Immunophenotypic Characteristics and Quantitative Differences of Telocytes Between Invasive Breast Cancer Subtypes

## TL;DR

This study compares telocyte counts and markers in different breast cancer subtypes, finding significant differences that may relate to tumor behavior.

## Contribution

The study reveals novel quantitative and immunophenotypic differences in telocytes across breast cancer subtypes.

## Key findings

- Telocyte counts for vimentin, CD10, CD34, and c-Kit were higher in Luminal and HER2(+) subtypes compared to TNBC.
- ER(+) and PR(+) patients showed higher CD10, CD34, and c-Kit telocyte counts than ER(–) and PR(–) patients.
- c-Kit(+) telocyte counts were lower in larger tumors, suggesting a potential role in tumor size regulation.

## Abstract

Background: Breast cancer is the most commonly diagnosed neoplasm in women and is classified into different molecular subtypes based on the expression characteristics of estrogen and progesterone receptors (ERs and PRs) and human epidermal growth factor 2 (HER2, ERBB2): Luminal A, Luminal B, HER2(+), and triple-negative breast cancer (TNBC). Telocytes, a new type of stromal cell, provide structural support for the preservation of organ integrity and play a crucial role in the tumor microenvironment. In this study, we evaluated telocyte counts and expression profiles among breast cancer subtypes. Methods: The quantitative differences between telocytes in three subtypes of invasive breast cancer were assessed via immunohistochemistry, using vimentin, CD10, CD34, and c-Kit antibodies. Results: Vimentin(+), CD10(+), CD34(+), and c-Kit(+) telocyte counts were significantly higher in the Luminal and HER2(+) groups than in TNBC (p = 0.000 for vimentin, CD10, CD34, and c-Kit in Luminal vs. TNBC; p = 0.006 for CD34 in HER2(+) vs. TNBC). CD10(+), CD34(+), and c-Kit(+) telocyte counts were significantly higher in ER(+) than in ER(–) patients (p = 0.006, p = 0.000, and p = 0.009, respectively) and in PR(+) than in PR(–) patients (p = 0.018, p = 0.000, and p = 0.044, respectively). The presence of ER/c-Kit(+) telocytes was demonstrated, and c-Kit(+) telocyte counts were significantly lower in tumors larger than 5 cm than in those measuring 2–5 cm (p = 0.032). Conclusions: Our results showed quantitative differences and marker expression profiles for telocytes between different breast cancer molecular subtypes. c-Kit(+) telocytes may contribute to the regulation of tumor size.