Cell type accuracy of bronchial biopsy specimens in primary lung cancer

To evaluate the diagnostic accuracy of bronchial biopsy (BB) specimens in establishing the specific cell type in primary lung cancer (LC), and to study the influence of several factors on this accuracy.

Tertiary health-care center.

One hundred forty-six patients with LC diagnosed by BB specimens who underwent thoracotomy (T).

We have studied the specific LC cell type observed in the BB specimen and compared it with the T specimen (reference diagnosis). Age, location and type of bronchial lesion, number and size of the biopsy fragments, tumoral size, sample necrosis, degree of cell differentiation, tumoral stage, pathologist's experience, and the presence of other diagnostic tests with the same cell type were analyzed to assess their influence on the concordance between the two diagnoses.

The overall concordance between BB and T histologic diagnosis was 0.70 (kappa coefficient [K]). Of the different histologic types, the worst result was obtained in large cell carcinoma (LLC) (K, 0.49). Squamous carcinoma and adenocarcinoma gave similar results (0.74 and 0.77, respectively), while small cell lung cancer (SCLC) only reached a value of 0.60. The degree of cell differentiation, the absence of necrosis, and presence of other preoperative diagnoses were the variables that most influenced the histologic accuracy of BB specimens. Therefore, the probability of BB accuracy was 2.7, 7.7, and 25 times higher in well-differentiated, than in poorly differentiated, moderately differentiated, or undifferentiated carcinomas; 5.2 times higher when there was no necrosis in the sample; and 7.43 higher when there was another preoperative diagnosis.

The histologic results of BB must be examined carefully, especially in cellular subtypes like LLC. The absence of differentiation and presence of necrosis in BB samples were the factors that require the greatest caution in ascertaining the cell type. When they are involved and also in all cases in which identifying the specific cell type has important implications, we prefer to classify the patients as having SCLC or non-small cell lung cancer, and then reclassify them later after using a second diagnostic technique.