Variable fidelity of tissue-marking dyes in surgical pathology

Three dyes for use in tissue marking inks for biopsies and other small specimens

In histological processing, the loss of a small biopsies can prevent diagnosis by the pathologist. Appropriate specimen marking dyes are helpful, but those sold for the purpose have trade-secret components. The purpose of this study is to find suitable dyes with known chemistry to improve the visibility of small specimens. Samples of various organs, including stomach, lung, nasopharynx, small intestine and sentinel lymph nodes, were labeled with Rose red D-FR (CI 282855, Direct red 227), Blue 2RL (CI 24315, Direct blue 80), and Purple D-5BL (CI 29120, Direct violet 66). Clinical pathologists evaluated the dyeing capability and determined any interference of the marking dyes with diagnosis of stained sections. Direct red 227, Direct blue 80, and Direct violet 66 all increased the visibility of small specimens, without interfering with hematoxylin & eosin (HE) staining or immunohistochemistry. All three dyes can therefore be recommended for marking small specimens such as biopsies.

Identification of Optimal Tissue-Marking Dye Color for Pathological Evaluation in Fluorescence Imaging Using IRDye800CW

PURPOSE

Fluorescence-guided surgery using a tumor-specific antibody-dye conjugate is useful in various cancer types. Fluorescence imaging is a valuable tool both intraoperatively and postoperatively for ex vivo imaging. The color of inks used for tumor specimens during ex vivo specimen processing in pathology is an important consideration for fluorescence imaging since the absorption/emission of the dyes may interfere with the fluorescent dye. This study assesses suitable ink colors for use specifically with IRDye800CW fluorescence imaging.

PROCEDURES

Eight tissue-marking inks or dyes (TMDs) commonly used for pathological evaluation were assessed. Agarose tissue-mimicking phantoms containing Panitumumab-IRDye800CW were used as an initial model. Mean fluorescence intensity was measured at 800 nm using both Pearl Trilogy as a closed-field fluorescence imaging system and pde-neo II as an open-field fluorescence imaging system before and after TMD application. An in vivo mouse xenograft model using the human head and neck squamous cell carcinoma FaDu cell line was then used in conjunction with TMDs.

RESULTS

The retained IRDye800CW fluorescence on Pearl Trilogy was as follows: yellow at 91.0 ± 4.5%, red at 90.6 ± 2.7%, orange at 88.2 ± 2.2%, violet at 56.6 ± 1.1%, lime at 40.9 ± 1.8%, green at 19.3 ± 2.8%, black at 13.3 ± 0.6%, and blue at 8.1 ± 0.2%. The retained IRDye800CW fluorescence on pde-neo II was as follows: yellow at 86.5 ± 6.4%, red at 77.0 ± 6.2%, orange at 76.9 ± 2.8%, lime at 72.5 ± 9.5%, violet at 59.7 ± 0.4%, green at 30.1 ± 6.9%, black at 17.0 ± 2.7%, and blue at 6.7 ± 1.7%. The retained IRDye800CW fluorescence in yellow and blue TMDs was 42.1 ± 14.9% and 0.2 ± 0.2%, respectively in the mouse experiment (p = 0.039).

CONCLUSION

Yellow, red, and orange TMDs should be used, and blue and black TMDs should be avoided for evaluating tumor specimens through fluorescence imaging using IRDye800CW.

Mapping of the perigastric lymphatic network using indocyanine green fluorescence imaging and tissue marking dye in clinically advanced gastric cancer

BACKGROUND

Using indocyanine green (ICG) fluorescence imaging and tissue marking dyes (TMDs), perigastric lymphatic mapping and their pathological correlation were examined to see whether ICG staining covers all metastatic lymph nodes (LNs) in advanced gastric cancer (AGC).

METHODS

Patients with AGC who underwent open distal or total gastrectomy were enrolled. ICG was serially injected intraoperatively into the subserosa along the greater and lesser curvatures. Stomach specimens were examined under a near-infrared camera. ICG-stained LNs were named, excised, and tattooed with different colored TMDs to retrace the exact location after pathological examinations.

RESULTS

A total of 687 LNs and 69 LN stations were examined from 11 patients. The map of the perigastric lymphatic network showing the topography of ICG-stained and ICG-unstained LNs, including metastatic information, was successfully reconstructed. The average number of ICG-stained and ICG-unstained LNs were 23.6 ± 12.3 (37.8%) and 38.8 ± 17.1 (62.2%), respectively. LN metastases were present in 28 LN stations of 8 patients. Of 8 cases with LN metastases, 40% (11.1-75% per case) of metastatic LNs were stained by ICG. Of 28 metastatic LN stations, 21 (75.0%) were covered by ICG, and actual metastatic LNs were stained in 16 LN stations (57.1%). In 4/8 cases (50%), all metastatic LN stations showed ICG signals.

CONCLUSIONS

ICG fluorescence imaging and TMD are useful tools for visualizing the perigastric lymphatic network and retracing the exact location of ICG-stained LNs in AGC. However, ICG imaging is still not recommended for selective LN dissection in AGC because of the limited staining of perigastric LNs.

Alteration of Tissue Marking Dyes Depends on Used Chromogen during Immunohistochemistry

Pathological biopsy protocols require tissue marking dye (TMD) for orientation. In some cases (e.g., close margin), additional immunohistochemical analyses can be necessary. Therefore, the correlation between the applied TMD during macroscopy and the examined TMD during microscopy is crucial for the correct orientation, the residual tumour status and the subsequent therapeutic regime. In this context, our group observed colour changes during routine immunohistochemistry. Tissue specimens were marked with various TMD and processed by two different methods. TMD (blue, red, black, yellow and green) obtained from three different providers (A, B and C, and Whiteout/Tipp-Ex^®) were used. Immunohistochemistry was performed manually via stepwise omission of reagents to identify the colour changing mechanism. Blue colour from provider A changed during immunohistochemistry into black, when 3,3′-Diaminobenzidine-tetrahydrochloride-dihydrate (DAB) and H₂O₂ was applied as an immunoperoxidase-based terminal colour signal. No other applied reagents, nor tissue texture or processing showed any influence on the colour. The remaining colours from provider A and the other colours did not show any changes during immunohistochemistry. Our results demonstrate an interesting and important pitfall in routine immunohistochemistry-based diagnostics that pathologists should be aware of. Furthermore, the chemical rationale behind the observed misleading colour change is discussed.

Nanomechanics and Histopathology as Diagnostic Tools to Characterize Freshly Removed Human Brain Tumors

Background

The tissue-mechanics environment plays a crucial role in human brain physiological development and the pathogenesis of different diseases, especially cancer. Assessment of alterations in brain mechanical  properties during cancer progression might provide important information about possible tissue abnormalities with clinical relevance.

Methods

With atomic force microscopy (AFM), the stiffness of freshly removed human brain tumor tissue was determined on various regions of the sample and compared to the stiffness of healthy human brain tissue that was removed during neurosurgery to gain access to tumor mass. An advantage of indentation measurement using AFM is the small volume of tissue required and high resolution at the single-cell level.

Results

Our results showed great heterogeneity of stiffness within metastatic cancer or primary high-grade gliomas compared to healthy tissue. That effect was not clearly visible in lower-grade tumors like meningioma.

Conclusion

Collected data indicate that AFM might serve as a diagnostic tool in the assessment of human brain tissue stiffness in the process of recognizing tumors.

Analysis and Comparison of Tissue-Marking Dye Detection via Light Microscopy, Telemicroscopy, and Virtual Microscopy

Objectives

To examine the fidelity of ink color identification using light microscopy (LM), telemicroscopy (TM), and virtual microscopy (VM).

Methods

Twenty H&E-stained frozen section slides, prepared after tissue inking with five stain combinations, were assessed by three pathologists using LM, TM, and VM. TM was performed using Mikroscan D2 slide scanner/LiveQ software with various objectives. VM was performed using Mikroscan D2 scanner/Qumulus software, specimens digitized at20×.

Results

Sensitivity/specificity by LM was 100%/100% for all colors. TM showed high overall specificity but poor sensitivity, particularly red (54%). VM showed high specificity for all colors except black (69%) and, consequently, poor sensitivity for all colors except black (96%).

Conclusions

TMD identification via telepathology showed loss of sensitivity/specificity vs LM and highlighted the need for caution when interpreting TMDs with digital technologies and the need for validation protocols.