Cytology Reporting System for Lung Cancer from the Japan Lung Cancer Society and Japanese Society of Clinical Cytology: An Interobserver Reproducibility Study and Risk of Malignancy Evaluation on Cytology Specimens

Abstract

Introduction: The classification of lung carcinoma is based on small biopsies and/or cytology in 80% of patients with non-small cell carcinoma. However, there is no widely accepted classification system for respiratory cytology. The Japan Lung Cancer Society (JLCS) and Japanese Society of Clinical Cytology (JSCC) have proposed a new four-tiered cytology reporting system for lung carcinoma with the following categories: (1) "negative for malignancy," (2) "atypical cells," (3) "suspicious for malignancy," and (4) "malignancy."

Objective: The aim of this work was to perform an interobserver reproducibility study to confirm the utility of the four-tiered reporting system on respiratory cytological samples.

Methods: We analyzed 90 cytological samples obtained with bronchoscopy. Seven observers classified these cases into each category by reviewing one Papanicolaou-stained slide per case according to the three-, four-, and five-tiered reporting systems.

Results: The interobserver agreement was fair in the three- (κ = 0.50), four- (κ = 0.45), and five-tiered (κ = 0.45) reporting systems. However, the four-tiered reporting system provided more precise information than the three-tiered reporting system in patient management. The risk of malignancy in the four-tiered reporting system was also stratified well: 19.3% for "negative for malignancy," 45.6% for "atypical cells," 74.7% for "suspicious for malignancy," and 88.1% for "malignancy."

Conclusions: The reporting system proposed by the JLCS and JSCC was designed to enhance the communication between clinicians and pathologists and among different institutions. It is simple and applicable to cytological diagnosis of any respiratory diseases. We propose establishing an international classification for respiratory cytology, harmonizing the reporting systems proposed by different countries.

Keywords: Classification; Cytology; Lung carcinoma; Reporting system; Risk of malignancy.

Fig. 1

a Case 6. Tumor cells obtained with bronchial brushing from a patient with adenocarcinoma. The nuclei of tumor cells are large, and nucleoli are prominent. The nuclear membrane is irregular. All 7 observers diagnosed this case as adenocarcinoma. b Case 24. Atypical cells obtained with bronchial brushing from a patient with abnormal shadow on chest roentgenogram. The cluster comprised atypical cells, nuclei were large, nucleoli were prominent, nuclear membranes were irregular, and cannibalism was observed. However, atypical cells were observed only in this cluster on a glass slide. Five observers evaluated this case as malignant and 2 as suspicious for malignancy. Tumor cells were not obtained with transbronchial biopsy, and follow-up of chest roentgenogram and clinical findings did not show any sign of malignancy. c Case 80. Atypical cells obtained via bronchial brushing in a patient with acute interstitial pneumonia. Nuclei are large and nucleoli are prominent; however, there is no nuclear hyperchromatism, and the nuclear membrane is smooth. Three out of 7 observers evaluated this case as malignant.

Fig. 2

a Distribution of cytological cate­gories in each final clinicopathological diagnosis with the three-tiered reporting system. b Distribution of cytological cat­egories in each final clinicopathological diagnosis with the four-tiered reporting system. Negative, negative condition, inflammatory condition, and benign tumor; Malignant, malignant tumor. The numbers within the bars show the absolute number of cases in each category.

Fig. 3

Distribution of the number of concordant observers in each reporting system.

Fig. 4

Distribution of the number of concordant observers in each reporting system after combining “suspicious for malignancy” and “malignancy” in the four- and five-tiered reporting systems.

Fig. 5

Number of agreements of cytological diagnosis among 7 observers in the four-tiered reporting system. Negative, negative condition, inflammatory condition, and benign tumor; Malignant, malignant tumor. The numbers within the bars show the absolute number of the cases in each category.

Fig. 6

Number of agreements of cytological diagnosis of each observer with clinicopathological diagnosis in the four-tiered reporting system. “Suspicious for malignancy” and “malignancy” categories were regarded as agreement in malignant tumors, and the “negative for malignancy” and “atypical cells” categories were regarded as agreement in negative cases. Negative, negative condition, inflammatory condition, and benign tumor; Malignant, malignant tumor. The numbers within the bars show the absolute number of cases in each category.