18-Fluorine fluorodeoxyglucose positron emission tomography in the pretreatment evaluation of thymic epithelial neoplasms: a metabolic biopsy confirmed by Ki-67 expression

Eur J Cardiothorac Surg. 2014 Sep;46(3):369-74; discussion 374. doi: 10.1093/ejcts/ezu030. Epub 2014 Feb 28.


Objectives: To investigate the usefulness of 18-fluorine fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET-CT) in the pretreatment evaluation of thymic epithelial neoplasms (TENs). We previously demonstrated that the ratio between standardized uptake value of the tumour and aortic arch (SUV T/M) correlates with World Health Organization (WHO) classification. We now focused our evaluation on thymomas only, excluding carcinomas. We also searched for the expression of a pathological biomarker, Ki-67, that gained both diagnostic and prognostic relevance for various solid tumours. Its correlation with SUV T/M and WHO classification was evaluated.

Methods: We performed a retrospective dynamic cohort study of data from January 2006 to December 2012, on 23 consecutive patients with pathologically proven TEN, excluding thymic carcinomas, evaluated with PET-CT. For each patient, SUV T/M was calculated. The patients were then categorized, according to WHO classification, into two groups (low-risk: 3 A, 9 AB, 5 B1; high-risk: 5 B2, 1 B3) and Ki-67 labelling index (LI) was defined. We employed the Spearman rank non-linear correlation coefficient (ρ) to estimate the correlations between variables.

Results: SUV T/M proved to be significantly higher for high-positive Ki-67 samples, indicating a strong correlation between SUV T/M and Ki-67 LI (ρ = 0.8). Furthermore, high Ki-67 LI samples correlate with the higher-risk WHO subgroup (ρ = 0.9).

Conclusions: FDG PET-CT can provide a useful tool in the preoperative work-up of TEN, reflecting its proliferation capacity, as described also by the Ki-67 expression. In particular, SUV T/M could provide a 'metabolic biopsy' to divide TEN into high-risk and low-risk neoplasms.

Keywords: Ki-67; PET–CT; Thymoma.

MeSH terms

  • Adult
  • Female
  • Fluorodeoxyglucose F18*
  • Humans
  • Ki-67 Antigen / analysis
  • Ki-67 Antigen / biosynthesis*
  • Male
  • Middle Aged
  • Neoplasm Staging / methods
  • Neoplasms, Glandular and Epithelial / diagnostic imaging*
  • Neoplasms, Glandular and Epithelial / metabolism
  • Neoplasms, Glandular and Epithelial / pathology*
  • Positron-Emission Tomography / methods*
  • Radiopharmaceuticals
  • Retrospective Studies
  • Thymus Neoplasms / diagnostic imaging*
  • Thymus Neoplasms / metabolism
  • Thymus Neoplasms / pathology*
  • Tomography, X-Ray Computed


  • Ki-67 Antigen
  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18

Supplementary concepts

  • Thymic epithelial tumor