Determining Adequacy of Cell Block Material for Molecular Testing: A Practical Guide for Cytopathologists

s S81 Figure 2 Increased background staining with Ventana Figure 3 No background staining with Dako 175 Determining Adequacy of Cell Block Material for Molecular Testing: A Practical Guide for Cytopathologists Oana Rafael, MD, Melissa Klein, CT(ASCP), Tamar Brandler, MD, MS, Kasturi Das, MD, Mohamed Aziz, MD. North Shore Long Island Jewish Lenox Hill Hospital, New York, New York; Hofstra North Shore e Long Island Jewish School of Medicine, New Hyde Park, New York Introduction: With the current advances in personalized medicine, targeted therapy has changed the practice of cytology. Selection of cell blocks (CB) for molecular testing (MT) is challenging when confronted with limited lesional material. Our aim was to determine optimal tumor quantity necessary for reliable MT results. Material and Methods: Reports for cytology cases were tallied for MT requests received between January 2012-December 2013. Cases were divided into satisfactory and unsatisfactory, with positive and negative molecular results (Table 1). Retrospective review of hematoxylin and eosin CB slides for 41 cases with MT was performed. CBs were evaluated for total number and percentage of tumor cells, background necrosis, inflammation, blood, and benign cells (Table 2). Results: Of 41 CBs analyzed, 59% were sufficient and 41% were insufficient for MT. Half of the reviewed cases showed positive MT results (Table 3). 17% (2/12 cases) of satisfactory CBs sent for MT were deemed inadequate by the reference laboratory, despite the cytopathologist’s count of 300-350 tumor cells (30% and 15% of tumor cells respectively) on CBs. In these cases, 20% malignant cellularity was given as a cut-off by the reference laboratory. However, in one case the pathologist appreciated tumor cellularity as Conclusions: Improved feedback from the reference laboratories might help ensure that sufficient material is present in cytology specimens before cytopathologists order MT. This study underscores the need for an algorithm to accurately assess adequacy of CBs before initiating molecular studies. These findings could serve as a guideline for pathologists and reference laboratories. Review of additional cases will be completed to support our CB adequacy threshold. Table 1 Cell block (CB) adequacy material for molecular testing CB adequacy material 2012 2013 Total Insufficient 23 12 35 Sufficient with positive molecular result 22 8 30 Sufficient with negative molecular result 37 32 69 TOTAL 82 52 134 Table 2 Evaluation of cell blocks for molecular testing, including distribution of tissue slides over the different tumor cell content categories Tumor Molecular Testing cell % Satisfactory with positive results Satisfactory with negative results Cases (n) Tumor Cells (n) Background* Cases (n) Tumor Cells (n) Background* 350 2+ blood 4 250-300 2+ benign cells >350 1+ blood 300-350 3+ blood 300-350 2+ necrosis 20% 3 >350 Clean 1 >350 2+ inflammation 2+ blood 3+ blood 25% 2 >350 1+ blood e e e 3+ blood 30% 4 >350 2+ necrosis 2 >350 Clean 1+ necrosis 3+ blood 1+ blood 1+ blood 35% e e e 1 >350 2+ inflammation 40% e e e 1 >350 Clean 70% 1 >350 3+ necrosis e e e * 1+ mild; 2+ moderate; 3+ abundant Table 3 Cases analyzed and molecular testing results Cell block adequacy material N (%) Total cases Sufficient with positive molecular result 12 (59) 41 Sufficient with negative molecular result 12 (59) Insufficient for molecular testing 17 (41)