# The three-dimensional landscape of tumor-associated macrophages in reactive and neoplastic human lymph nodes

## TL;DR

This study explores how tumor-associated macrophages in lymph nodes change in 3D space, revealing patterns linked to specific cancers and their functions.

## Contribution

A hybrid approach combining computer vision and graph algorithms is used to analyze 3D TAM patterns in human lymph nodes across multiple diagnoses.

## Key findings

- Distinct TAM patterns were identified in chronic lymphocytic leukemia and diffuse large B-cell lymphoma.
- TAMs showed compact arrangements correlated with known functional interactions in Hodgkin-Reed-Sternberg cell environments.
- 3D analysis revealed entity-specific pathomic alterations that reflect functional aberrations in TAMs.

## Abstract

Macrophages play a crucial role in the homeostasis of lymph nodes. Their phenotypes and functions are dictated by the molecular composition of the microenvironment. The presence of tumor cells can influence the microenvironment, leading to changes in the cellular functions of tumor-associated macrophages (TAMs). Cellular alterations often correlate with histomorphometric and distributional changes. This study aims to characterize these pathomic modifications resulting from tumor cell infiltration by comparing them to reactive conditions. We assessed CD68+ and CD163+ TAMs in 160 three-dimensional (3D) images of human lymphoid tissue sections derived from 82 cases comprising six different diagnoses. To investigate TAM profiles, we employed a hybrid approach involving computer vision and graph theoretical algorithms. For calculating the histomorphometric features of TAMs, we utilized an image analysis pipeline with IMARIS Advanced Tracking Software. The distributions of TAMs were characterized using cell graphs. The incorporation of 3D tissue analysis in targeted areas of thick tissue sections revealed specific patterns of histomorphometric and distributional changes in TAMs. In chronic lymphocytic leukemia and diffuse large B-cell lymphoma, these distinctive alteration patterns demonstrated entity specificity. Furthermore, pathomic alterations displayed possible correlations with established functional aberrations in lymphomas. These findings imply that the pathomic properties of TAMs mirror their functional aberrations. Through validation and generalization via molecular pathological examinations, this approach has the potential to unveil and understand functional aberrations in histopathological assessments.

Macrophages play a pivotal role in the homeostasis of lymph nodes. The phenotype and function are intricately linked to the molecular environment. The emergence of tumors can disrupt this environment, inducing alterations in tumor-associated macrophages (TAMs). These changes are observable and analyzable through three-dimensional (3D) imaging. In this investigation, we analyzed 160 3D images of human lymph node tissue sections from six different diagnoses to elucidate the characteristics of TAMs. Employing a hybrid approach that integrates computer vision and graph algorithms, we aimed to identify entity-specific patterns.The findings revealed distinct TAM patterns in cases of chronic lymphocytic leukemia and diffuse large B-cell lymphoma. Known patterns of heightened interactions between TAMs and Hodgkin-Reed-Sternberg cells could be also correlated with revealed compact arrangements of TAMs in the microenvironment. This underscores that established functional aberrations of TAMs are, to some extent, mirrored in their pathomic properties. Overall, our results demonstrate that such hybrid workflows can provide new perspectives on TAM-related neoplastic aberrations and thereby contribute to a deeper understanding of tumorigenesis.