Integrative analysis of small cell carcinoma of the uterine cervix reveals its heterogeneity and provides novel predictive markers

Small cell carcinoma of the uterine cervix (UCSCC) is a rare and aggressive HPV-linked neuroendocrine malignancy with limited therapeutic options and poor prognosis. Through integrative analysis of whole-exome sequencing (WES), single-cell RNA-seq (scRNA-seq), PinpoRNA-HPV, bulk RNA-sequencing, and immunohistochemistry (IHC), we delineated its molecular architecture. Genomic profiling unveiled the dysregulation of 10 core oncogenic pathways and an exceptionally high tumor mutational burden (TMB), along with frequent alterations in DNA repair genes. ScRNA-seq analysis identified nine distinct malignant subclusters characterized by lineage plasticity (ASCL1/NEUROD1/UCHL1) alongside active HPV18 transcription. The tumor microenvironment exhibited a paradoxical immune landscape: dense infiltration of CD8+ T cells and CD163+ tumor-associated macrophages (TAMs) in the complete absence of tumoral PD1/PD-L1 expression. Cell-cell communication analysis revealed that malignant subclusters specifically overexpress CD47, engaging SIRB1 on TAMs and SIRPG on T cells. IHC validation confirmed a CD8+/CD163+/PD-L1-phenotype and demonstrated that transcriptional CD47 enrichment in malignant clones implicated the CD47-SIRB1 axis as the primary immune checkpoint. These findings indicated UCSCC as an HPV-driven, heterogeneous tumor that might employ CD47 as an alternative immune evasion pathway in the absence of PD-L1, providing a strong rationale for exploring CD47 blockade as a novel potentially therapeutic strategy.