Joan and Melissa Rivers

Joan and Melissa Rivers speak during the E! Entertainment Television lunch panel during the NBCUniversal portion of the 2012 Winter TCA Tour on Jan. 7, 2012, in Pasadena, Calif.

Andy Kropa/Getty Images for Mercedes-Benz Fashion Week

From left, Martha Stewart, Joan Rivers and Star Jones attend the Dennis Basso Fall 2013 fashion show during Mercedes-Benz Fashion Week at The Stage at Lincoln Center on Feb. 12, 2013, in New York.

Joan and Melissa Rivers take a Gray Line New York Sightseeing tour with Melissa's son, Cooper and his friend. They took the Downtown Loop and saw sights such as Times Square, Greenwich Village and more.

AP Photo/Jennifer Graylock, TV Guide Magazine

Comediennes Kathy Griffin and Joan Rivers are seen during a party to celebrate TV Guide Magazine's Power List and 3,000th issue.

Melissa and Joan Rivers pose for a photo July 1, 2004.

Joan Rivers looks at beads during the Krewe of Orpheus parade in the Uptown area of New Orleans Feb. 23, 2009.

Joan and Melissa Rivers pose for photographers as they arrive for the 43rd annual Grammy Awards Feb. 21, 2001, at the Staples Center in Los Angeles.

Melissa Rivers arrives at Nickelodeon's 24th Annual Kids' Choice Awards April 2, 2011, in Los Angeles.

Melissa Rivers attends the 34th Annual Gracie Awards in New York June 3, 2009.

Melissa and Joan Rivers arrive at the 58th Annual Primetime Emmy Awards at the Shrine Auditorium Aug. 27, 2006, in Los Angeles.

Joan and Melissa Rivers are seen on the red carpet for Oscar arrivals before the 77th annual Academy Awards Feb. 27, 2005, in Los Angeles.