Swiss drugmaker Roche Holding is buying U.S. - based Bioimagene for some $100 million, making another bolt-on acquisition to cement its dominant position in tissue-based cancer diagnostics.

Diagnostics is gaining more importance in cancer treatment, which is being increasingly dovetailed to the genetic profile of patients. Roche is the world's largest maker of cancer drugs.

"As part of the personalised healthcare approach, pathologists are increasingly involved in generating information with high impact on treatment decisions," Daniel O'Day, chief operating officer at Roche Diagnostics, said in a statement.

Bioimagene's products create high-resolution, whole-slide digital images from glass microscope slides. The privately held group also provides the software to view, analyse and manage tissue images using a computer.

"We view the bolt-on acquisition as a good complement to the existing offering in tissues diagnostics, which is becoming increasingly important and crucial for personalised therapy options," Kepler Capital Markets analyst Martin Voegtli said in a note.