Supernatant DNA Plus Pancreatic Fine-Needle Aspiration

Jim Kling

November 09, 2011

November 9, 2011 (Las Vegas, Nevada) — Pancreatic fine-needle aspiration samples can have low cellularity or too much sample variation; in such cases, DNA from the supernatant can be used to conduct complementary mutational analysis, according to a study presented here at the American Society for Clinical Pathology 2011 Annual Meeting.

"I think the extracellular fluid in and around a neoplasm is a kind of enriched source of DNA, as well as RNA and proteins and other analytes. Why not tap it instead of discarding it?" Sydney Finkelstein, MD, chief scientific officer at RedPath in Pittsburgh, Pennsylvania, who presented the research, suggested to Medscape Medical News.

The team collected supernatant fluid from 14 patients who had undergone fine-needle aspiration for solid or cystic lesions. The fluid was mixed with Saccomanno's fixative to a volume of 5 to 10 mL. The team then quantified extracted DNA using optical density, and determined its integrity using quantitative polymerase chain reaction (qPCR).

There was enough DNA in the supernatant fluid to conduct a broad panel of mutation analysis, and qPCR confirmed the presence of amplifiable free DNA.

The researchers conducted mutational analysis using 17 markers, including KRAS point mutation and loss of heterozygosity at 1p, 3p, 5q, 9p, 10q, 17p, 17q, 21q, and 22q. The team also Pap-stained the pelleted cells and conducted a microdissection.

KRAS point mutations were found in 5 of 14 cases (36%). One sample had 2 separate KRAS point mutations. Three of 14 cases (21%) had loss of heterozygosity mutational change.

When corresponding cytology was available for microdissection and comparison, the mutational profile of the supernatant was equivalent or superior to the microdissected cytology for the purposes of mutation detection. The researchers detected mutations in 3 acellular cytology samples.

"It's a very good idea to use the supernatant, which a number of people are discarding. It's a natural extension," Selwyn J. Baptist, MD, chair of the Department of Pathology at St. Barnabas Medical Center in Livingston, New Jersey, who attended the session, told Medscape Medical News.

RedPath donated analytical services to the study. Dr. Finkelstein is the chief executive officer of RedPath. Dr. Baptist has disclosed no relevant financial relationships.

American Society for Clinical Pathology (ASCP) 2011 Annual Meeting: Abstract 321. Presented October 21, 2011.