The Role of Mean Platelet Volume (MPV) in Thyroid Cancers: A Scoping Review

<i>Background and Objectives</i>: Mean platelet volume (MPV) is a routinely available blood marker that measures platelet size and activation, and it has been evaluated as a potential marker for thyroid malignancies. Platelets participate in tumor genesis through angiogenesis, immune evasion, and metastasis, making them plausible adjuncts for cancer risk evaluation. The objective is to systematically evaluate the role of MPV in thyroid cancers, with the main focus on diagnostic accuracy, prognostic value, and limitations, focusing on papillary thyroid carcinoma (PTC). <i>Materials and Methods</i>: A systematic search of PubMed was conducted from January 2015 to September 2025. Only free full-text studies on human subjects were included. Eligible studies included case-control, cohort, or observational designs reporting MPV or platelet indices in thyroid cancer compared with benign nodules or healthy controls. Data on diagnostic performance, associations with tumor stage, lymph node involvement, and recurrence were extracted and synthesized narratively. No formal risk-of-bias or study quality assessment tool was applied. The literature search was restricted to studies with freely available full-text articles, which may have introduced access-based selection bias. <i>Results</i>: Eleven studies met the inclusion criteria. Most of them reported high MPV values in papillary thyroid carcinoma (PTC), with limited evidence regarding other thyroid cancer subtypes. High values of MPC were reported in the majority of studies in PTC compared to benign nodules or healthy controls. The diagnostic performance of MPV alone was poor, but integration with inflammatory ratios such as the neutrophil-to-lymphocyte ratio (NLR) or platelet-to-lymphocyte ratio (PLR), and with ultrasound systems (TI-RADS), improved accuracy. Regarding prognostic utility, some studies linked higher MPV with lymph node involvement or recurrence risk, while others did not find significant data. Thyroid function, autoimmune thyroid disease, and methodological variability in MPV measurement limited comparability across studies. <i>Conclusions</i>: MPV is a low-cost adjunct biomarker, especially when combined with other hematologic and imaging markers. However, MPV should not be used as a stand-alone diagnostic or prognostic tool. Larger, prospective studies are mandatory to clarify its clinical role.