Malassezia Patterns in Basal Cell Carcinoma

Evidence

This observational tissue-characterization study combined molecular detection in basal cell carcinoma (BCC) specimens with fungal community sequencing and epithelial cell experiments. Paraffin-embedded tissue samples from 50 patients with BCC were retrieved from the Department of Pathology at Jingzhou Hospital affiliated with Yangtze University between 2023 and 2024. Three patients with biopsy-confirmed BCC undergoing surgery at the same hospital provided paired tumor and adjacent normal tissue for fresh-tissue analysis. The investigation therefore linked a retrospective archived-tissue cohort to a much smaller paired fresh-tissue component and laboratory models rather than following patients over time. pmid:42708973

Archived formalin-fixed, paraffin-embedded (FFPE) blocks underwent reverse-transcription quantitative polymerase chain reaction screening, while paired fresh tumor-peritumoral samples underwent metagenomic mycobiome sequencing. Adjacent normal samples were collected during surgery at least 5 mm from the tumor margin and with a minimum size of 5 mm. For functional experiments, the investigators exposed HaCaT keratinocytes and A-431 epidermoid carcinoma cells to Malassezia globosa or Malassezia yamatoensis, then assessed proliferation with Cell Counting Kit-8 and 5-ethynyl-2′-deoxyuridine assays. Transcriptome sequencing followed by reverse-transcription quantitative polymerase chain reaction validation assessed inflammatory and oxidative-stress-related gene responses in those cell lines. pmid:42708973

The archived-tissue cohort ranged in age from 34 to 90 years, with a reported mean age of 66.7 years. Its disease duration, defined as the interval from initial skin-lesion detection to histopathologic confirmation through surgery or biopsy, ranged from 3 months to 54 years; the median duration was 3 years overall. These descriptive data characterize the enrolled, histologically verified BCC cohort and do not provide a comparator population without BCC. pmid:42708973

Malassezia globosa was reported as the most abundant species in FFPE samples and was also detectable in fresh tissues. The available evidence describes tissue-associated fungal detection and relative abundance within the studied BCC materials. It does not convert detection in archived specimens or in three paired fresh-tissue sets into evidence about the direction of the observed relationship between fungal colonization and BCC lesions. pmid:42708973

After 12 hours of stimulation, M. globosa at 1.2 × 10 7 colony-forming units per milliliter and M. yamatoensis at 1.6 × 10 7 colony-forming units per milliliter significantly promoted epithelial-cell proliferation in the tested HaCaT and A-431 lines. Both strains also significantly upregulated interleukin-1 beta, interleukin-6, tumor necrosis factor alpha, superoxide dismutase 1, and superoxide dismutase 2 in these models. No exact effect estimate, confidence interval, or exact p-value for these reported proliferation and gene-expression findings was located in the available evidence. pmid:42708973

Analysis — Association and laboratory scope

The results form an observed pattern consistent with the study’s selection process: Malassezia was characterized in tissues from people already diagnosed with BCC, and two selected strains produced proliferative and gene-expression responses in cultured epithelial lines. The paired fresh-tissue comparison was limited to three tumor-peritumoral pairs, whereas the larger 50-patient component used archived FFPE material for molecular screening. Thus, the human-tissue findings describe colonization patterns in a selected BCC cohort, while the Cell Counting Kit-8, 5-ethynyl-2′-deoxyuridine, transcriptome-sequencing, and validation results are confined to HaCaT keratinocytes and A-431 epidermoid carcinoma cells under the stated stimulation conditions. The retrospective design cannot establish causation. Statistical significance for the laboratory endpoints does not by itself establish clinical significance, because the packet supplies neither patient outcomes tied to fungal measurements nor quantitative effect estimates for those cellular endpoints. The study’s interpretation of a correlative association is consequently narrower than a claim that Malassezia causes BCC or that the in vitro phenotypes occur in BCC patients. pmid:42708973

Limitations

Selection limits generalizability: only histologically verified BCC patients were enrolled, and the evidence does not describe a non-BCC or other-skin-lesion comparison group. The modest archived cohort and the three-pair fresh-tissue sequencing cohort represent different components of the investigation, so they should not be treated as interchangeable evidence. The retrospective design cannot establish causation, and tissue fungal characterization does not measure longitudinal exposure, lesion development, or patient outcomes. pmid:42708973

Technical limitations also constrain the molecular findings. Formalin fixation, paraffin embedding, and prolonged storage can degrade DNA integrity and partially affect the sensitivity and specificity of nucleic-acid-based detection in FFPE tissues. The investigators reported insufficient matched fresh tissue for systematic culture-based validation; they also noted that cross-contamination could skew species-level results from FFPE sections. For metagenomic sequencing, the fresh-tissue cohort comprised three pairs and lacked extraction blanks or no-input library controls. These constraints matter particularly when interpreting species-level fungal measurements from low-volume tissue material. pmid:42708973

Finally, the laboratory models were not BCC-specific. HaCaT keratinocytes and A-431 epidermoid carcinoma cells can document responses within those tested systems, but their results do not establish the same responses in BCC tissue or patients. The reported inflammatory and oxidative-stress-related transcriptional changes are preliminary mechanistic clues from cell culture, while the proposed tumor-permissive epithelial microenvironment remains a hypothesis requiring BCC-specific and in vivo evaluation. pmid:42708973