. Step 35 of 41
Clinical Stem 1
Non-smoking female with a new right upper lobe lung mass and three PET-positive mediastinal lymph nodes

Answer A
It is important to assure that samples contain adequate cellularity and representative tissue for analysis. Care should be taken to avoid wasting tissue on unnecessary IHC investigations, and to conserve as much tissue as possible for molecular analysis when indicated. Because the literature suggests that specimens should contain at least 50?70% tumor cells for mutation analysis, sending specimens directly for molecular testing without a pathologist's review for quality and quantity is not recommended.

In this patient, specimens were available for analyzing markers predictive of response and/or resistance to certain chemotherapeutic agents and molecular targets. Evidence suggests that high expression of TS, for example, could predict resistance to pemetrexed. Initiating chemotherapy without performing molecular testing may not be cost effective.
Operators collecting small specimens should carefully use appropriate smear techniques, attempt to obtain tissue cores, and communicate on-site with the pathologists to assure samples are adequate and processed appropriately.
References:
  1. Pirker R, et al. Consensus for EGFR mutation testing in non-small cell lung cancer: results from a European workshop. Thorac Oncol. 2010;5:1706-13
  2. Takezawa K, et al. Identification of thymidylate synthase as a potential therapeutic target for lung cancer et al. Br J Cancer 2011;104:1594-1601
Each fictitious clinical case scenario is based on a conglomerate of real patient data. Cases have been modified to avoid any possibility for patient identification and to help meet educational objectives. Any resemblance to real persons, living or deceased, is purely coincidental.

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