CAP TODAY Pathology/Laboratory Medicine/Laboratory Management
Karen Lusky
April 2016—In his CAP ’15 presentation last fall, David Bostwick, MD, MBA, referred to intraductal carcinoma of the prostate as “sort of the rage right now in the urologic pathology field.”
“The problem is that it has multiple different definitions, and interobserver agreement with it is moderate at best,” said Dr. Bostwick, medical director of Granger Diagnostics in Richmond, Va. Even when pathologists can agree on an IDC diagnosis, he said, they aren’t on the same page about treatment.
Dr. Zhou
“By definition, intraductal carcinoma itself is not invasive,” Ming Zhou, MD, PhD, said in a CAP TODAY interview. “In most cases, intraductal carcinoma represents the spread of invasive cancer into the preexisting prostate ducts and glands. So the intraductal carcinoma glands will have retained their basal cells,” said Dr. Zhou, a professor of pathology and urology and director of surgical pathology and urologic pathology at New York University Medical Center Tisch Hospital in New York City.
Laurence Klotz, MD, a urologic oncologist at Sunnybrook Health Sciences Centre and a professor of surgery at the University of Toronto, said intraductal carcinoma “is really a sign that there’s aggressive disease elsewhere. It’s also quite rare so that’s part of its strength. When you find it, you have to take it seriously.”
How rare? Dr. Zhou and colleagues found that the prevalence of IDC in prospectively collected prostate biopsies was about 2.8 percent (Watts K, et al. Histopathology. 2013;63[4]:574–579), which means, he said, that about three out of 100 biopsies may have a lesion that could be diagnosed as IDC. “But most of these intraductal carcinomas are associated with invasive cancer in the same biopsy. Only about one-tenth of those IDCs have so-called isolated intraductal carcinoma without invasive carcinoma. So it’s very rare.” Before diagnosing isolated IDC, pathologists have to be sure they haven’t overlooked invasive cancer, Dr. Zhou cautions.
The differential diagnosis for IDC, he said, includes high-grade PIN, ductal carcinoma of the prostate, urothelial carcinoma involving the prostate, and invasive cribriform cancer. “But the most important differential diagnosis is between high-grade PIN and IDC.”
Dr. Zhou noted that the National Comprehensive Cancer Network guideline does not advise repeating a biopsy within the first year of a high-grade PIN diagnosis when the high-grade PIN involves a single core on a standard 12-core biopsy. “In contrast, IDC is almost always associated with high-grade and [high]-volume cancer,” he said. “Therefore, a diagnosis of IDC without concomitant cancer warrants immediate biopsy.” Some experts recommend radical prostatectomy or radiation therapy.
In very rare cases, IDC is considered to be a precursor lesion just like high-grade PIN, Dr. Zhou said. “There is a gray zone between the two because you’re talking about a continuous spectrum of moving from a relatively low-grade proliferation to a high-grade proliferation.” Moving along this spectrum, “in the IDC, you typically see an expansile, complex, cribriform, and solid proliferation. The cytological atypia is much more pronounced” than in high-grade PIN.
Kenneth Iczkowski, MD, an associate professor of pathology at Medical College of Wisconsin, said if the lesion has marked enough cytological atypia and is distending the duct space it is in, those two features are most influential in diagnosing IDC. “Also, if there’s necrosis in the lumen of the gland or the cellularity of the cribriform proliferation is dense, those findings support IDC.”