Faculty Bibliography

Since the 2015 WHO classification was introduced into clinical practice, the importance of immunohistochemistry (IHC) has figured prominently in lung cancer diagnosis. In addition to distinction of small versus non-small cell carcinoma (NSCC), patients' treatment of choice is directly linked to histological subtypes of NSCC, which pertains to IHC results, particularly for poorly-differentiated tumors. The use of IHC has improved diagnostic accuracy in the lung carcinoma classification, but the interpretation remains challenging in some instances. Also, pathologists must be aware of many interpretation pitfalls, and the use of IHC should be efficient to spare the tissue for molecular testing. The IASLC Pathology Committee received questions on practical application and interpretation of IHC in lung cancer diagnosis. After discussions in several IASLC Pathology Committee meetings, the issues and caveats were summarized as eleven key questions, which cover common and important diagnostic situations in a daily clinical practice with some relevant challenging queries. The questions included best IHC markers for distinguishing NSCLC subtypes, differences in TTF1 clones, utility of IHC in diagnosing uncommon subtypes of lung cancer and distinguishing primary from metastatic tumors." This article provides answers and explanations for the key questions about the use of IHC in lung carcinoma diagnosis representing viewpoints of experts in thoracic pathology that should assist the community in the appropriate use of IHC in diagnostic pathology.

We assessed a priori aggressive features using quantitative diffusion-weighted imaging metrics to preclude an active surveillance management approach in patients with papillary thyroid cancer (PTC) with tumor size 1-2 cm. This prospective study enrolled 24 patients with PTC who underwent pretreatment multi-b-value diffusion-weighted imaging on a GE 3 T magnetic resonance imaging scanner. The apparent diffusion coefficient (ADC) metric was calculated from monoexponential model, and the perfusion fraction (f), diffusion coefficient (D), pseudo-diffusion coefficient (D*), and diffusion kurtosis coefficient (K) metrics were estimated using the non-Gaussian intravoxel incoherent motion model. Neck ultrasonography examination data were used to calculate tumor size. The receiver operating characteristic curve assessed the discriminative specificity, sensitivity, and accuracy between PTCs with and without features of tumor aggressiveness. Multivariate logistic regression analysis was performed on metrics using a leave-1-out cross-validation method. Tumor aggressiveness was defined by surgical histopathology. Tumors with aggressive features had significantly lower ADC and D values than tumors without tumor-aggressive features (P < .05). The absolute relative change was 46% in K metric value between the 2 tumor types. In total, 14 patients were in the critical size range (1-2 cm) measured by ultrasonography, and the ADC and D were significantly different and able to differentiate between the 2 tumor types (P < .05). ADC and D can distinguish tumors with aggressive histological features to preclude an active surveillance management approach in patients with PTC with tumors measuring 1-2 cm.

Fine needle aspiration cytology (FNAC) of mediastinal masses allows for rapid on-site evaluation and the triaging of material for ancillary studies. However, surgical pathology is often considered to be the gold standard for diagnosis. This study examines the sensitivity and specificity of FNAC compared to a concurrent or subsequent surgical pathology specimen in 77 mediastinal lesions. The overall sensitivity for mediastinal mass FNAC was 78% and the overall specificity was 98%. For individual categories the sensitivity and specificity of FNAC was respectively as follows: inflammatory/infectious (33%, 99%), metastatic carcinoma (93%, 100%), lymphoma (84%, 97%), cysts (25%, 100%), soft tissue tumors (100%, 100%), paraganglioma (50%, 100%), germ cell tumor (100%, 99%), thymoma (87%, 94%), thymic carcinoma (60%, 100%), benign thymus (0%, 100%), and indeterminate (100%, 90%). For different locations within the mediastinum the sensitivity and specificity of FNAC was respectively as follows: anterosuperior mediastinum (80%, 98%), posterior mediastinum (33%, 95%), middle mediastinum (100%, 100%), and mediastinum, NOS (79%, 99%). Thus, mediastinal FNAC is fairly sensitive, very specific, and is a valuable technique in the diagnosis of mediastinal masses.