Comparative morphology of tumour microenvironment in claudin-low and claudin-high breast cancers.

Background: Claudin-low breast cancers (BCs) exhibit more aggressive behaviour compared to claudin-high types. Claudin-low BCs are often characterized by features such as a higher grade, enrichment of stemness characteristics, and a propensity for metastasis. Tumour microenvironment (TME) defined as the intricate network of surrounding cells, blood vessels, and extracellular matrix components influences the behaviour of cancer cells within the breast tissue. Understanding the TME is crucial for comprehending the aggressive characteristics of claudin-low BCs.

Methods: In this study, we have studied the morphology of immune and non-immune TME using Haematoxylin and eosin (H&E)-stained slides of 15 claudin-low and 12 claudin-high tissue samples of BC.

Results: TME of claudin-low BCs was observed to have a significantly higher frequency of retraction clefts (66.6 %; n = 10/15), immature desmoplastic response (40 %; n = 6/15), higher stromal cellularity (60 %; n = 9/15); and fibroblastic proliferation (53.3 %; n = 8/15) with a low prevalence of elastosis (66.6 %; n = 10/15). The immune microenvironment revealed a higher frequency of total (80 %; n = 12/15) as well as stromal (86.67 %; n = 13/15) and intra-tumoural TILs (60 %; n = 9/15) in them.

Conclusion: The above morphology-based study revealed that claudin-low tumours have unique immune and non-immune TME as compared to claudin-high tumours. Future studies exploring the molecular correlates of each of the above morphological features can help in identifying novel therapeutic targets for the treatment of claudin-low BCs.