Lida P. Hariri

The traditional surgical pathology assessment requires tissue to be removed from the patient, then processed, sectioned, stained, and interpreted by a pathologist using a light microscope. Today, an array of alternate optical imaging technologies allow tissue to be viewed at high resolution, in real time, without the need for processing, fixation, freezing, or staining. Optical imaging can be done in living patients without tissue removal, termed in vivo microscopy, or also in freshly excised tissue, termed ex vivo microscopy. Both in vivo and ex vivo microscopy have tremendous potential for clinical impact in a wide variety of applications. However, in order for these technologies to enter mainstream clinical care, an expert will be required to assess and interpret the imaging data. The optical images generated from these imaging techniques are often similar to the light microscopic images that pathologists already have expertise in interpreting. Other clinical specialists do not have this same expertise in microscopy, therefore, pathologists are a logical choice to step into the developing role of microscopic imaging expert. Here, we review the emerging technologies of in vivo and ex vivo microscopy in terms of the technical aspects and potential clinical applications. We also discuss why pathologists are essential to the successful clinical adoption of such technologies and the educational resources available to help them step into this emerging role.

Background: Transbronchial needle aspiration (TBNA), often used to sample lymph nodes for lung cancer staging, is subject to sampling error even when performed with endobronchial ultrasound. Optical coherence tomography (OCT) is a high-resolution imaging modality that rapidly generates helical cross-sectional images. We aim to determine if needle-based OCT can provide microstructural information in lymph nodes that may be used to guide TBNA, and improve sampling error. Methods: We performed ex vivo needle-based OCT on thoracic lymph nodes from patients with and without known lung cancer. OCT imaging features were compared against matched histology. Results: OCT imaging was performed in 26 thoracic lymph nodes, including 6 lymph nodes containing metastatic carcinoma. OCT visualized lymphoid follicles, adipose tissue, pigment-laden histiocytes, and blood vessels. OCT features of metastatic carcinoma were distinct from benign lymph nodes, with microarchitectural features that reflected the morphology of the carcinoma subtype. OCT was also able to distinguish lymph node from adjacent airway wall. Conclusions: Our results demonstrate that OCT provides critical microstructural information that may be useful to guide TBNA lymph node sampling, as a complement to endobronchial ultrasound. In vivo studies are needed to further evaluate the clinical utility of OCT in thoracic lymph node assessment.

This work establishes a new class of endoscopic optical imaging catheters, termed nano-optic endoscopes, that uses metalenses with the ability to modify the phase of incident light at sub-wavelength level. We utilize the control of the phase and chromatic dispersion of the output beam to address two persistent limitations of optical imaging system, namely optical aberrations and the trade-off between transverse resolution and depth-of-focus. High-resolution endoscopic imaging at an extended depth-of-focus is demonstrated in resected human lung specimens and the airways of sheep in vivo. The nano-optic endoscope elevates the capabilities of endoscopic imaging in examining pathological changes in luminal tissue.

Optical coherence tomography (OCT) is a nondestructive, high-resolution imaging modality, providing cross-sectional, architectural images at near histologic resolutions, with penetration depths up to a few millimeters. Optical frequency domain imaging is a second-generation OCT technology that has equally high resolution with significantly increased image acquisition speeds and allows for large area, high-resolution tissue assessments. These features make OCT and optical frequency domain imaging ideal imaging techniques for surface and endoscopic imaging, specifically when tissue is unsafe to obtain and/or suffers from biopsy sampling error. This review focuses on the clinical impact of OCT in coronary, esophageal, and pulmonary imaging and the role of the pathologist in interpreting high-resolution OCT images as a complement to standard tissue pathology.

Silicone, commonly used in cosmetic procedures owing to its presumed inertness, can yield serious sequelae including acute embolization and pneumonitis. Chronic pulmonary sequelae in response to silicone injection have not been previously described. We report a case of chronic progressive granulomatous pneumonitis in response to subcutaneous silicone injections in a transgender male-to-female patient infected with human immunodeficiency virus 1 (HIV-1). After receiving silicone injections to the buttock, the patient developed rapid onset dyspnea, pleuritic chest pain, fever, and chills. Chest computed tomography revealed diffuse peripheral interstitial opacities. She responded symptomatically to prednisone with subsequent intermittent symptomatic flares. Four years later, she developed marked dyspnea and cough. Chest computed tomography showed progressive diffuse ground-glass and nodular opacities. Lung biopsies demonstrated numerous spheroid silicone particles within the lung interstitium and small pulmonary vessels, surrounded by foreign body giant cells and nonnecrotizing granulomatous inflammation. We speculate that HIV-1–infected patients may be at risk for chronic, progressive granulomatous pneumonitis due to silicone injection years after their procedure owing to shifting levels of cell-mediated immunity.

Pulmonary manifestations of systemic lupus erythematosus (SLE) typically include pleuritis, alveolar hemorrhage, and infectious pneumonia due to immunosuppression with less common entities including bronchiolitis, interstitial pneumonia, and pulmonary fibrosis. More rare manifestations include organizing pneumonia (OP) and diffuse alveolar damage (DAD). A similar but distinct entity of acute fibrinous and organizing pneumonia (AFOP), characterized by intra-alveolar fibrin deposition and associated organizing pneumonia, has been reported in association with connective tissue disorders, but has not been described in association with SLE. Reported herein is a patient with SLE and accompanying antiphospholipid syndrome with recent pulmonary embolism, persistent respiratory symptomology, and persistent radiographic abnormalities who underwent lung biopsy displaying features of AFOP. This case in conjunction with previous literature indicates that AFOP can be a manifestation of connective tissue disease including SLE and may be an underreported variant of medical lung disease due to overlap in histological characteristics with OP and DAD.

Intracoronary optical frequency domain imaging (OFDI) provides high resolution, three-dimensional views of coronary artery microstructure, but requires a non-occlusive saline/contrast purge to displace blood for clear artery views. Recent studies utilized manual pullback initiation/termination based on real-time image observation. Automated pullback initiation/termination by real-time OFDI signal analysis would enable more efficient data acquisition. We evaluate the use of simple imaging parameters to automatically and robustly differentiate between diagnostic-quality clear artery wall (CAW) versus blood-obstructed fields (BOF). Algorithms are tested using intracoronary OCT human data retrospectively and intracoronary OFDI swine and human data prospectively. In prospective analysis of OFDI swine data, the sensitivity and specificity of the ratio of second and first moments (contrast parameter) were 99.6% and 97.2%, respectively. In prospective analysis of OFDI clinical data, the contrast parameter yielded 96.0% sensitivity and 94.5% specificity. Accuracy improved further by analyzing sequential frames. These results indicate the algorithm may be utilized with intracoronary OFDI for initiating and terminating automated pullback and digital data recording.