BACKGROUND: Guidelines for histological subtyping in patients with surgically resected lung adenocarcinoma (ADC) were recently proposed by the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society. The objective of the current study was to investigate the cytomorphology of these subtypes of ADC in cases with matched histology specimens demonstrating a single pure subtype. METHODS: The authors reviewed their database for patients with histological diagnoses of primary lung ADC with a single histological pattern observed on surgical resection and investigated the cytological findings in 18 matched cytology specimens to eliminate sampling issues in cases of mixed ADC. RESULTS: Resections were classified as acinar (7 specimens), solid (6 specimens), lepidic (2 specimens), mucinous (2 specimens), and papillary (1 specimen). Cytology specimens demonstrating a solid pattern had a predominance of 3-dimensional clusters (5 of 6 vs 0 of 12 specimens) (P = .0007, Fisher exact test), necrotic background (3 of 6 vs 0 of 12 specimens) (P = .02), pleomorphic nuclei (6 of 6 vs 1 of 12 specimens) (P = .0004), irregular nuclear contours (6 of 6 vs 3 of 12 specimens) (P = .009), and nuclear enlargement (5 of 6 vs 2 of 12 specimens) (P = .01) compared with the nonsolid patterns. Nuclear pseudoinclusions were present only in nonsolid patterns (5 of 12 specimens), although this finding was not statistically significant (P = .05) CONCLUSIONS: Cytological features of lung ADC subtypes proposed by the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification overlap. However, architectural and nuclear features may be helpful, particularly in distinguishing the prognostically adverse solid pattern from other patterns.
BACKGROUND: Guidelines for histological subtyping in patients with surgically resected lung adenocarcinoma (ADC) were recently proposed by the International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society. The objective of the current study was to investigate the cytomorphology of these subtypes of ADC in cases with matched histology specimens demonstrating a single pure subtype. METHODS: The authors reviewed their database for patients with histological diagnoses of primary lung ADC with a single histological pattern observed on surgical resection and investigated the cytological findings in 18 matched cytology specimens to eliminate sampling issues in cases of mixed ADC. RESULTS: Resections were classified as acinar (7 specimens), solid (6 specimens), lepidic (2 specimens), mucinous (2 specimens), and papillary (1 specimen). Cytology specimens demonstrating a solid pattern had a predominance of 3-dimensional clusters (5 of 6 vs 0 of 12 specimens) (P = .0007, Fisher exact test), necrotic background (3 of 6 vs 0 of 12 specimens) (P = .02), pleomorphic nuclei (6 of 6 vs 1 of 12 specimens) (P = .0004), irregular nuclear contours (6 of 6 vs 3 of 12 specimens) (P = .009), and nuclear enlargement (5 of 6 vs 2 of 12 specimens) (P = .01) compared with the nonsolid patterns. Nuclear pseudoinclusions were present only in nonsolid patterns (5 of 12 specimens), although this finding was not statistically significant (P = .05) CONCLUSIONS: Cytological features of lung ADC subtypes proposed by the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification overlap. However, architectural and nuclear features may be helpful, particularly in distinguishing the prognostically adverse solid pattern from other patterns.
Keywords:
International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society (IASLC/ATS/ERS) classification; adenocarcinoma; adenocarcinoma subtype; cytology; lung