[1625] Interobserver Variability in the Cytologic Diagnosis and Sub-Classification of Primary Lung Tumors

AB O'Bannon, H Alatassi, MG Sanders, S Sahoo. University of Louisville Hospital, Louisville, KY

Background: CT-guided fine-needle aspiration biopsy (FNAB) is widely accepted as an accurate and safe procedure for characterizing lung nodules prior to treatment. The challenge for the pathologist is not only to distinguish malignant from benign lesions, but also to sub-classify the type of malignant tumors in order to facilitate management.
Design: Three pathologists (a cytopathology fellow, a general pathologist without fellowship training, and a board certified cytopathologist) blindly reviewed cytology smears from 62 consecutive cases of primary lung tumor in an attempt to distinguish small cell carcinoma (SCC) from non-small cell carcinomas (NSCC) and to further subclassify the NSCCs. To assess interobserver variation, the diagnoses of the 3 reviewers were compared to one another and to the final diagnosis which included evaluation of cell block, small core biopsy and immunostains.
Results: In all 62 cases, at least one of the pathologists made the correct diagnosis. Table 1 lists the interpretations made by each pathologist. Overall, the correct classification of SCC vs NSCC was high (90%). The fellow and practicing cytopathologist correctly categorized SCC in all cases whereas the general pathologist classified 3 SCCs as NSCC. All the NSCCs were correctly identified by the general pathologist and cytopathologist, however, the fellow misclassified 3 NSCCs as SCC. In the subclassifcation of NSCC, there was complete agreement by all three pathologists in 23/47 cases (49%) and argreement by two of three pathologists in 36/47 cases (77%). These include cases of squamous cell carcinoma with some degree of keratinization and cases of adenocarcinoma showing any glandular differentiation. The cases with discordant diagnoses were poorly differentiated NSCC (adenosquamous, adenocarcinoma and non-keratinizing squamous cell carcinoma).

Table 1. Summary of interpretations.

Tumor Types	# of cases	Fellow	General Pathologist	Cytopathologist	% of cases with unanimous agreement
SCC	13	13	10	13	77
NSCC	47	44	47	47	94
Squamous cell carcinoma	22	20	19	19	68
Adenocarcinoma	16	11	11	13	50
NSCC, nos	9	4	3	3	33
Mixed SCC & NSCC	1	1	1	1	100
Carcinoid tumor	1	1	0	1	0
Total	62	50	49	55	90

Conclusions: In majority of cases, FNAB alone can correctly classify lung tumors as SCC or NSCC. Subclassification of poorly differentiated NSCCs can easily be achieved by a consensus approach or by using ancillary studies if needed.
Category: Pulmonary

Monday, March 9, 2009 11:15 AM

Platform Session: Section F, Monday Morning