Subtyping of Non-Small Cell Lung Carcinoma into Adenocarcinoma and Squamous Cell Carcinoma by Cytological Structural Features.

INTRODUCTION: This study aimed to clarify the diagnostic structural features in cytology specimens that are useful in subtyping non-small cell lung carcinoma (NSCLC) into adenocarcinoma (ADC) and squamous cell carcinoma (SQCC). METHODS: Cytology specimens (n = 233) of NSCLCs, which included ADCs (n = 149) and SQCCs (n = 84), were analyzed. The following cytological features were evaluated: isolated cell, flat sheet, three-dimensional cluster with irregular arrangement, papillary-like structure, micropapillary-like structure, acinar-like structure, palisading pattern, protrusion of nuclei at the periphery of the cluster, honeycomb pattern, streaming arrangement, three-dimensional sheets with regular arrangement, flattening at the periphery of the cluster, fuzzy pattern at the periphery of the cluster, and mutual inclusion. RESULTS: ADCs exhibited significantly higher frequencies of flat sheet (p < 0.001), papillary-like structure (p < 0.001), micropapillary-like structure (p = 0.028), acinar-like structure (p < 0.001), and protrusion of nuclei at the periphery of the cluster (p < 0.001) than SQCCs. The latter exhibited significantly higher frequencies of streaming arrangement (p < 0.001), three-dimensional sheets with regular arrangement (p < 0.001), flattening at the periphery of the cluster (p < 0.001), fuzzy pattern at the periphery of the cluster (p < 0.001), and mutual inclusion (p < 0.001) than ADCs. DISCUSSION: Cytological structural features, such as flat sheet, papillary-like structure, micropapillary-like structure, acinar-like structure, and protrusion of nuclei at the periphery of the cluster, indicated ADC, whereas streaming arrangement, three-dimensional sheets with regular arrangement, flattening at the periphery of the cluster, fuzzy pattern at the periphery of the cluster, and mutual inclusion indicated SQCC. Paying attention to these cytological structural features can enable the accurate subtyping of NSCLC into ADC and SQCC.

Cytology Reporting System for Lung Cancer from the Japan Lung Cancer Society and the Japanese Society of Clinical Cytology: An Extensive Study Containing More Benign Lesions.

INTRODUCTION: The Japan Lung Cancer Society (JLCS) and the Japanese Society of Clinical Cytology (JSCC) have proposed a new four-tiered cytology reporting system for lung carcinoma (JLCS-JSCC system). Prior to the proposal, the Papanicolaou Society of Cytopathology (PSC) had proposed a revised reporting system (PSC system), which comprises the "neoplastic, benign neoplasm, and low-grade carcinoma" category (N-B-LG category), in addition to the 4 categories of the JLCS-JSCC system. This study aimed to evaluate the interobserver agreement of the JLCS-JSCC system with an additional dataset with more benign lesions in comparison with the PSC system. METHODS: We analyzed 167 cytological samples, which included 17 benign lesions, obtained from the respiratory system. Seven observers classified these cases into each category by reviewing one Papanicolaou-stained slide per case according to the JLCS-JSCC system and PSC system. RESULTS: The interobserver agreement was moderate in the JLCS-JSCC (k = 0.499) and PSC (k = 0.485) systems. Of the 167 samples, 17 samples were benign lesions: 7 pulmonary hamartomas, 5 sclerosing pneumocytomas, 2 squamous papillomas, one solitary fibrous tumor, one meningioma, and one lymphocytic proliferation. There were diverse sample types as follows: 11 touch smears, 3 brushing smears, 2 aspirations, and one sputum sample. Fourteen samples (82.3%) were categorized into "negative" or "atypical" by more than half of the observers in the JLCS-JSCC system. Conversely, 3 samples were categorized as "suspicious" or "malignant" by more than half of the observers in the JLCS-JSCC system. On the other hand, 11 samples (64.7%) were categorized into the N-B-LG category by more than half of the observers in the PSC system. CONCLUSIONS: The concordance rate in the JLCS-JSCC system was slightly higher than that in the PSC system; however, the interobserver agreement was moderate in both the JLCS-JSCC and PSC systems. These results indicate that both the JLCS-JSCC and PSC systems are clinically useful. Therefore, both systems are expected to have clinical applications. It may be important to integrate the 2 systems and construct a universal system that can be used more widely in clinical practice.