Dr. Alexander Breslow, 52, a pathologist at George Washington University Medical Center and an authority on the diagnosis and treatment of melanoma, died Sunday at George Washington University Hospital. He had cancer.

Dr. Breslow joined the GW medical center in 1961 as an assistant professor of pathology. His most recent position there was chief of surgical pathology and director of the division of anatomic pathology.

Dr. Breslow was best known for his work on melanoma, a type of skin cancer.

He devised the Breslow Method, a widely used technique for determining the treatment of melanoma and addressed the 10th Annual International Cancer Congress last year.

Dr. Breslow was born in New York City. He received his undergraduate and medical degrees at the University of Chicago. He was an intern with the U.S. Public Health Service in Baltimore and then became a clinical associate at the National Cancer Institute in Bethesda. He later served a residency in pathology at Massachusetts General Hospital in Boston.

In 1959, he became an instructor in the pathology department of the University of Washington in Seattle. He remained there until he joined the staff at the GW medical center. He became a full professor there in 1974 and was named director of the division of anatomical pathology last year.

Dr. Breslow was a member of the International Academy of Pathologists and served on the World Health Organizaton's melanoma group. He also was a member of the American Association of Pathologists, the American Society of Clinical Pathology, the College of American Pathologists and the Washington Society of Pathologists, of which he was a past president.

Survivors include his wife, Ruth Weilerstein Breslow of Bethesda, where the family lived; three daughters, Faith R., of Boston, Abbey Breslow-Kellogg of South Hadley, Mass., and Rachel D., of Bethesda; two brothers Dr. Lawrence Beslow of Glencoe, Ill., and Dr. David Breslow of Wilmington, Del., and a sister Mildred Novick of Patchogue, N.Y.

The family suggests that expressions of sympathy be in the form of contributions to the Alexander Breslow Memorial Fund, Department of Pathology, George Washington University Medical Center, 2300 I St. NW, Washington, 20037.