Unseeded when she won here last year, Pistolesi defeated Russia's Elena Likhovtseva, 6-3, 7-6 (7-3), to reach the quarterfinals. This was one of a career-high four titles won last season by Pistolesi, who next takes on American Jill Craybas.
Craybas posted a 6-4, 6-4 victory over countrywoman Meilen Tu to advance to her second career meeting with Pistolesi. The 28-year-old American topped Pistolesi in straight sets in the first round at Miami two years ago.
"This is the first time I've been directly in the main draw," said Craybas, who recorded her best career win here in 2001 when she beat top seed and world No. 17 Sandrine Testud in the second round. She won her first career title last year at the Japan Open and appeared in two other quarterfinals.
"This one would be very special to me," she said. "This is a tournament I always come back to. I stay with the same family and have made a lot of friends here."
Second seed Eleni Daniilidou of Greece routed Martina Muller of Germany, 6-3, 6-0. Daniilidou, a winner last year at 's-Hertogenbosch, conceded only eight points in the final set.
She will face fifth Paola Suarez of Argentina in the quarterfinals.
"She's a good player and a big name," Daniilidou said. "I feel better and I'm playing better now."
Suarez eliminated her doubles partner, Mary Pierce of France, 6-4, 4-6, 6-4. Pierce, a two-time Grand Slam winner, has been beset by injuries the past two years.
"Sometimes the harder I try the worst I play," the Frenchwoman said. "It's a bit confusing to me. I like to do well in every tournament I play in."
Also, Yoon Jeong Cho of Korea ousted sixth seed Clarisa Fernandez of Argentina, 7-5, 6-2; American Laura Granville dispatched Zimbabwe's Cara Black, 6-3, 6-2; and Russia's Vera Zvonareva bested Germany's Anca Barna, 6-3, 6-4.
American qualifier Ashley Harkleroad's run came to an end with a 6-2, 1-6, 7-6 (7-5) loss to Switzerland's Emmanuelle Gagliardi.