Comparison between optical coherence tomographic and histopathologic appearances of artifacts caused by common surgical conditions and instrumentation

Rate of residual tumor after repeat surgery for positive margins in ductal carcinoma in Situ, and predictive factors

AIMS

To evaluate the rate of residual tumor in re-excision specimen of patients with positive margins in ductal carcinoma in situ (DCIS) following breast-conservative surgery, and to identify predictive factors of residual tumor.

MATERIAL AND METHODS

We conducted a monocentric, retrospective study, from January 2010 to December 2020. All 103 patients who underwent re-excision for positive margins in DCIS following breast-conservative surgery for in situ or invasive breast carcinoma were included. Positive margins were defined as inferior to 2 mm from the DCIS component. Two groups were defined, depending on the presence of residual tumor or not, and were compared on their clinical and histopathological characteristics to identify predictive factors of residual tumor.

RESULTS

Residual tumor was found in re-excision specimen of 46 patients (44.7 %). The risk of residual tumor was increased in patients with more than 2 tumor foci (aOR: 12.4; 95 % CI: 1.2 -124.1; p = 0.032) and in those with extensive margin involvement (aOR: 3.2; 95 % CI: 1.3-8.2; p = 0.013). Finally, surgery performed after 2013 was associated with a lower risk of residual tumor (aOR: 0.23; 95 % CI: 0.09-0.058; p = 0.002).

CONCLUSION

The rate of residual tumor in re-excision specimen of patients with positive margins in DCIS is high. Both the number of tumor foci and the extension of positive margins were identified as risk factors. Finally, the surgical learning curve for this procedure seems to be significantly correlated with the risk of residual tumor and needs to be considered.

Morpho-molecular signal correlation between optical coherence tomography and Raman spectroscopy for superior image interpretation and clinical diagnosis

The combination of manifold optical imaging modalities resulting in multimodal optical systems allows to discover a larger number of biomarkers than using a single modality. The goal of multimodal imaging systems is to increase the diagnostic performance through the combination of complementary modalities, e.g. optical coherence tomography (OCT) and Raman spectroscopy (RS). The physical signal origins of OCT and RS are distinctly different, i.e. in OCT it is elastic back scattering of photons, due to a change in refractive index, while in RS it is the inelastic scattering between photons and molecules. Despite those diverse characteristics both modalities are also linked via scattering properties and molecular composition of tissue. Here, we investigate for the first time the relation of co-registered OCT and RS signals of human bladder tissue, to demonstrate that the signals of these complementary modalities are inherently intertwined, enabling a direct but more importantly improved interpretation and better understanding of the other modality. This work demonstrates that the benefit for using two complementary imaging approaches is, not only the increased diagnostic value, but the increased information and better understanding of the signal origins of both modalities. This evaluation confirms the advantages for using multimodal imaging systems and also paves the way for significant further improved understanding and clinically interpretation of both modalities in the future.

The feasibility and utility of optical coherence tomography directed histopathology for surgical margin assessment of canine mast cell tumours

Histopathologic surgical margin assessment in veterinary patients is an imprecise science with assessment limited to a small proportion of the surgical margin due to time and finances. Incomplete excision of canine mast cell tumours (MCTs) alters treatment recommendations and prognosis. Optical coherence tomography (OCT) is a novel imaging modality that has been reported in a single veterinary study for surgical margin assessment. Twenty-five dogs with 34 MCTs were enrolled in a prospective pilot-study to assess the imaging characteristics of canine MCTs with OCT and to evaluate the feasibility and utility of OCT-guided histopathology. All dogs underwent routine surgical excision of MCTs. OCT imaging was used to assess the entire surgical margin prior to placement in formalin. Either normal areas or areas suspected of incomplete MCT excision were inked. Standard histopathologic sectioning and tangential sectioning of inked areas were performed and compared to OCT results. OCT identified MCT near the surgical margin in 10 of 26 specimens (38.4%). Four specimens suspicious for incomplete margins on OCT had incomplete MCT excision that was missed on standard histopathologic sectioning. Six specimens had OCT-guided sections taken as suspicious, which did not show MCT on histopathology. OCT-guided pathology sections were able to detect incompletely excised MCT near the surgical margin with a sensitivity of 90% and specificity of 56.2% in this preliminary study. OCT imaging shows promise for guiding pathologists to areas of interest to improve the diagnostic accuracy of surgical margin assessment in excised canine MCTs.

Evaluating optical coherence tomography for surgical margin assessment of canine mammary tumours

Optical coherence tomography (OCT) uses near-infrared light waves to generate real-time, high-resolution images on the microscopic scale similar to low power histopathology. Previous studies have demonstrated the use of OCT for real-time surgical margin assessment for human breast cancer. The use of OCT for canine mammary tumours (CMT) could allow intra-operative visualisation of residual tumour at the surgical margins. The purpose of this study was to assess OCT imaging for the detection of incomplete tumour resection following CMT surgery. We hypothesized that the OCT images would have comparable features to histopathological images of tissues at the surgical margins of CMT resections along with a high sensitivity of OCT detection of incomplete surgical excision of CMT. Thirty surgical specimens were obtained from nineteen client-owned dogs undergoing surgical resection of CMT. OCT image appearance and characteristics of adipose tissue, skin, mammary tissue and mammary tumour at the surgical margins were distinct and different. The OCT images of normal and abnormal tissues at the surgical margins were utilized to develop a dataset of OCT images for observer evaluation. The sensitivity and specificity for ex vivo images were 83.3% and 82.0% (observer 1) and 70.0% and 67.9% (observer 2). The sensitivity and specificity for in vivo images were 70.0% and 89.3% (observer 1) and 76.7% and 67.9% (observer 2). These results indicate a potential use of OCT for surgical margin assessment for CMT to optimize surgical intervention and clinical outcomes. Improved training and experience of observers may improve sensitivity and specificity.

Optical coherence tomography imaging of excised canine apocrine gland anal sac adenocarcinoma tumours

Optical coherence tomography (OCT) is an optical imaging modality that has been investigated for real-time surgical margin evaluation in human breast cancer patients. Previous veterinary OCT studies have been limited to surgical margin imaging for soft tissue sarcoma (STS) tumours. To the authors knowledge, OCT has never been used to characterize or evaluate other types of neoplasia in dogs. The goal of this study was to characterize the OCT imaging appearance of apocrine gland anal sac adenocarcinoma (AGASACA) in excised ex vivo specimens from five client-owned dogs. All excised tissue surgical margins were imaged using a clinical spectral domain OCT system and two to four areas suspicious for incomplete surgical margins were selected. These areas were inked and sections were trimmed for histopathology. This enabled OCT imaging from each area of interest to be compared with corresponding H&E stained histology imaging from the same location. OCT was able to identify the presence of AGASACA at or within 1 mm of the surgical margin in all areas of interest. AGASACA, similar to the previously described canine STS, generated a dense, highly scattering image without any specific textural architecture. This study was able to validate the ability of OCT to accurately identify another type of tumour presence at or close to the surgical margin in the dog. Further study is needed to assess OCT accuracy at identifying other tumour types in dogs to understand its potential clinical applications.