Endogenous cyanide has recently been identified in mammals and implicated in regulating mitochondrial function and the response to hypoxia. It is hypothesized to act as a gasotransmitter with functional significance comparable to nitric oxide. Importantly, a fraction of endogenous cyanide exists as a covalently bound posttranslational modification, called S- cyanylation, and may be more feasible to study in clinical samples than cyanide in its gaseous form. We conducted a feasibility study to assess whether cyanylation can be detected and quantified in human Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD). We used anonymized, published clinical proteomics PXD051911 and standard computational tools. Cyanylation was detectable but very low abundance. We observed <1% cyanylated cysteines in every liver sample. In both control and MASLD livers, cyanylated proteins were observed in fatty acid oxidation and NRF2-mediated oxidative stress response pathways, as well as in pathways involved in degradation of alcohol, serine and adrenaline. The total amount of cyanylation was not associated with the presence of MASLD or fibrosis severity in the liver. However, granular quantitative analysis for cyanylated peptides was impossible because most of the unique peptide sequences were observed in only one or a few liver samples. We conclude that the quantitative studies of cyanylation in clinical samples are not feasible with standard methods. To enable meaningful analysis of this modification and optimize the use of experimental resources, future work will require targeted mass spectrometry assays with labelled cyanylated peptide standards or the development of other dedicated methodologies.