Circulating tumor cells (CTCs) invade blood vessels in solid tumors and promote metastases by circulating in the blood. CTCs are thus recognized as targets for liquid biopsy and can provide useful information for design of treatments. This diagnostic approach must consider not only the number of CTCs but also their molecular and genetic characteristics. For this purpose, use of devices that enrich CTCs independent of these characteristics and detectors that recognize various CTC characteristics is essential. In the present study, we developed a CTC detection system comprising ClearCell FX and ImageStream Mark II. We clarified the analytical performance of this system by evaluating recovery rate, lower limits of detection, and linearity. These parameters are critical for detecting rare cells, such as CTCs. We tested these parameters using three cell lines with different expression levels of the epithelial marker-epithelial cell adhesion molecule (EpCAM) and spiked these cells into whole-blood samples from healthy donors. The average recovery rate and lower limit of detection were approximately 40% and five cells/7.5 mL of whole blood, respectively. High linearity was observed for all evaluated samples. We also evaluated the ability of the system to distinguish between normal and abnormal cells based on protein expression levels and gene amplification and found that the system can identify abnormal cells using these characteristics. The CTC detection system thus displays the ability to distinguish specific characteristics of CTC, thereby providing valuable information for cancer treatment.

Background/Objectives: Liquid biopsy methods have gained prominence as minimally invasive tools to improve cancer treatment outcomes. Circulating tumor cells (CTCs) offer valuable insights into both primary and metastatic lesions. However, validating the CTC test results requires confirmation that the detected cells originate from cancer tissue. While studies have identified CTCs in colorectal cancer (CRC) patients using molecular markers, simultaneous validation of their cancer tissue origin remains unexplored. Methods: This study introduces a simple approach to detect adenomatous polyposis coli (APC) gene abnormalities alongside established CTC markers using a molecular imaging flow cytometer (MI-FCM). Given that APC gene abnormalities occur in 60–70% of CRC patients, their detection serves as strong evidence of cancer origin. Results: Our method achieved 92% concordance with DNA sequence analysis of tumor-derived cells. In a proof-of-concept study using 5 mL of whole blood from CRC patients, we observed a high frequency of cells exhibiting APC abnormalities, cytokeratin (CK), and vimentin (Vim) expression. Extending the study to 80 CRC patients across pathological stages I–IV confirmed CK and Vim as valid CTC markers. Three distinct cell populations were identified in blood: CK+/Vim−, CK+/Vim+, and CK−/Vim+. CTC number and frequency increased progressively with cancer stage. Conclusions: This is the first report demonstrating CK and Vim as effective markers for direct CTC detection in CRC patients. Our findings provide evidence-based validation of CTC markers, offering new insights and advancing approaches for patient care.

症例は46歳男性．腹痛，嘔気を主訴に前医を受診し，腸閉塞に対する加療目的に当院紹介受診．CTで上行結腸に腫瘤を認め，上行結腸癌に伴う腸閉塞と診断．イレウス管留置により症状は改善したが，留置後８日目に急激な左上腹部痛と限局的な圧痛，筋性防御を認め，イレウス管の排液が血性に変化した．CTにて空腸に腸重積を認め，同日緊急手術を行った．術中所見では，Treitz靭帯より約70cmの空腸が約30cmにわたり肛門側へ重積していた．腸重積の原因となるような腫瘍性病変は認めず，イレウス管が誘因になったと考えられた．腸管の色調不良を認め腸管虚血が疑われたため，同部位を切除した．また上行結腸癌に対する結腸右半切除術を併施した．成人の腸重積症の原因の多くは消化管の腫瘤性病変であり，イレウス管が原因とされるものは比較的稀である．今回，われわれはイレウス管が原因と考えられる腸重積の１例を経験したので報告する．