Mean Platelet Volume as a Biomarker for Thyroid Carcinoma

Thyroid malignancies constitute 3% of all malignancies, and are the most common type of endocrine malignancies.¹ Thyroid malignancies are between 2 and 4 times more common in women than men, and their incidence has increased in recent years.^2,3 Ultrasonography and fine-needle aspiration biopsy play important roles in the diagnosis and follow-up of thyroid nodules. These investigations have greatly facilitated the differentiation of benign from malignant thyroid nodules, and the selection of appropriate treatments.^4,5 In addition, a variety of parameters that are useful for the diagnosis and follow-up of thyroid nodules have been investigated. One such parameter is the mean platelet volume (MPV), which has been extensively researched in recent years.

MPV is an early indicator of platelet activation.^6,7 Platelets differ in terms of functional activity and size. Large platelets are relatively new, more reactive, and produce more thrombogenic factors.⁸ Therefore, in conditions that involve increased platelet activation, an increase in the proportion of young platelets (and thus, in MPV) is expected. Recent studies have indicated that MPV is an important marker of long-term mortality in ischemic cardiovascular disease.^9,10 Furthermore, increased MPV has been detected in a variety of malignancies.^11–13

In the present study, we aimed to determine the association between MPV and thyroid malignancies in patients who underwent surgery for benign or malignant thyroid diseases. To the best of our knowledge, our study is one of the only pioneer studies to compare the MPV values between patients with benign thyroid disease and those with thyroid malignancies.

Patients and Methods

We collected data retrospectively for this study. The analyses in this article were based on previously conducted studies, and did not involve any new tests on humans or any tests performed by any of the authors. In addition, the personal identifying information of patients was not included in the study.

We retrospectively reviewed the medical data of patients who had undergone total thyroidectomy at our institution for benign or malignant diseases of the thyroid between January 2012 and November 2014. The following data were collected: age, sex, MPV, white blood cell (WBC) count, hemoglobin level, and platelet count.

Patients aged <18 years, those with incomplete data, and those with Hashimoto thyroiditis, myocardial disorders, neurological disorders, diabetes mellitus, chronic renal failure, or chronic pulmonary diseases were excluded from the study, as chronic illnesses can affect platelet function.¹⁴

Statistical analysis was performed using statistical software (SPSS version 19.0; SPSS, Chicago, IL, USA). Normality was assessed using the Shapiro–Wilk test. For normally distributed values, descriptive results were expressed as the mean ± SD. The independent-samples t-test and Kruskal–Wallis test were used to examine differences between groups. Statistical significance was defined as P < 0.05.

Results

A total of 146 patients who had undergone total thyroidectomy for benign or malignant thyroid diseases were enrolled in this study. Diagnosis was made via histopathological examination: malignant disease was present in 47 patients, and benign disease was present in 99 patients. Age, sex, and hemoglobin levels did not significantly differ between patients with benign disease and those with malignant disease (Table 1). MPV was significantly higher in the malignant group than in the benign group (8.9 ± 1.1 fL versus 8.3 ± 0.8 fL, P = 0.002), but platelet counts were similar in the two groups (P = 0.159, Table 1). Similarly, WBC counts did not significantly differ between the malignant and benign groups (P = 0.092, Table 1).

Table 1 Demographic data and clinical characteristics of the study patients

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The graphical view demonstrated that MPV may be a discriminatory parameter between thyroid cancer and benign thyroid disease is shown in Figure 1.

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Discussion

Several clinical studies have investigated the association between platelet counts and survival times in cancer patients. Platelets have been suggested to play an important role in the progression and metastasis of cancer.¹⁵ Activated platelets secrete angiogenic growth factors, which contribute to tumor angiogenesis and thereby promote tumor formation.¹⁶ As the MPV is a significant predictor of platelet activation,¹⁷ we hypothesized that MPV might be related to thyroid malignancies. Kurt et al¹¹ have reported that MPV is high in patients with hepatocellular cancer and may be a diagnostic marker for this cancer. Osada et al¹² found significantly higher MPV values in gastric cancer patients than in healthy controls. Tuncel et al¹³ reported high MPV values in patients with metastatic colorectal cancer. Consistent with these studies, our study revealed significantly higher MPV values in patients with thyroid malignancies than in patients with benign thyroid disease. Collectively, the above findings suggest that MPV values are significantly increased in patients with malignant disease. However, Aksoy et al¹⁸ found lower MPV values in patients with various types of cancers that had metastasized to the bone marrow than in control subjects. Similarly, Mutlu et al¹⁹ did not find high MPV values in patients with various types of cancer, but did find low MPV values in patients who experienced thromboembolic events.

MPV has also been an important focus of research in benign thyroid disease. Erikci et al²⁰ detected significantly higher MPV values in patients with subclinical hypothyroidism than in healthy euthyroid controls. Carlioglu et al²¹ determined significantly higher MPV values in patients with euthyroid Hashimoto thyroiditis than in healthy controls. Although MPV values have also been found to be increased in certain benign diseases, the findings in our current study suggest that an overall increase in MPV values in malignant thyroid diseases was significantly higher than in patients with benign thyroid disorders.

In conclusion, our study, despite being limited by its retrospective design and small sample size, investigated the relationship between MPV and malignant thyroid diseases. The finding that MPV values are significantly higher in patients with a thyroid malignancy suggests that the MPV might be an important predictive biomarker for thyroid malignancies. Further prospective studies with a larger number of patients are required to validate our findings.