Background: Near-infrared optical imaging targeting the intrinsic contrast of tissue hemoglobin has emerged as a promising approach for visualization of vascularity in cancer research. We evaluated the usefulness of diffuse optical spectroscopy using time-resolved spectroscopic (TRS) measurements for functional imaging of primary breast cancer. Methods: Fifty-five consecutive TNM stageI/II patients with histologically proven invasive ductal carcinoma and operable breast tumors (<5 cm) who underwent TRS measurements were enrolled. Thirty (54.5%) patients underwent 18 F-fluoro-deoxy-glucose (FDG) positron emission tomography with measurement of maximum tumor uptake. TRS was used to obtain oxyhemoglobin, deoxyhemoglobin, and total hemoglobin (tHb) levels from the lesions, surrounding normal tissue, and contralateral normal tissue. Lesions with tHb levels 20% higher than those present in normal tissue were defined as "hotspots," while others were considered "uniform." The findings in either tumor type were compared with clinicopathological factors.

Near-infrared diffuse optical spectroscopy (DOS) imaging can non-invasively measure tumor hemoglobin concentration using high contrast to normal tissue, thus providing vascularity and oxygenation status. We assessed the clinical usefulness of DOS imaging in primary breast cancer. In all, 118 women with a histologically confirmed diagnosis of primary malignant tumor were enrolled. All participants underwent testing using time-resolved DOS before treatment initiation. Visual assessment of DOS imaging for detecting tumors was carried out by two readers blinded to the clinical data. Relative total hemoglobin (rtHb) and oxygen saturation (stO2) of the tumors was compared with clinicopathological variables and 10-year prognosis was calculated. Sensitivity for detecting a tumor based on the rtHb breast map was 62.7% (74/118). The sensitivity depended on T stage: 100% (7/7) for T3, 78.9% (45/57) for T2, 44.7% (17/38) for T1, and 31.3% (5/16) for Tis. Tumors showed unique features of higher rtHb with a wider range of stO2 than normal breast tissue, depending on histological type. There was a significant correlation of rtHb with tumor size, lymphatic vascular invasion, and histological grade, and of stO2 with age and tumor size. Neither rtHb nor stO2 correlated with intrinsic biomarkers such as estrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2; rtHb inversely correlated with 10-year relapse-free survival and overall survival, with statistical significance. Diffuse optical spectroscopy imaging has limited utility for the early detection of breast cancer; nonetheless, the findings suggest that the degree of tumor angiogenesis and hypoxia may be associated with tumor aggressiveness and poor prognosis.

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Recent advanced imaging modalities such as positron emission tomography (PET) detect malignancies using 2-[18F]-fluoro-2-deoxy-D: -glucose (18-FDG) with high accuracy, and they contribute to decisions regarding diagnosis, staging, recurrence, and treatment response. Here, we report a case of false-positive metastatic lymph nodes that were diagnosed by PET/CT and ultrasonography in a 48-year-old breast cancer patient who had undergone mastectomy. The tumors, which were oval shaped and resembled lymph nodes, were detected by ultrasonography. PET/CT revealed high uptake of 18-FDG in the tumors. To investigate the proposed recurrence and to re-evaluate the biology of the recurrent tumors, a tumor was removed from the brachial plexus of the patient. Histological findings revealed it to be a schwannoma. All imaging modalities including PET/CT failed to distinguish benign tumors from metastatic lymph nodes in the brachial plexus. After resection of the schwannomas, the patient complained of a slight motor disorder of the second finger on the right hand. Hence, it is important to consider a false-positive case of lymph node metastasis in a breast cancer patient following mastectomy.