Doctors have a variety of techniques to diagnose basal cell carcinoma (BCC) without making an incision, but the procedures may not be completely dependable, according to Ralph P. Braun, M.D.Dr. Braun heads the pigmented lesion clinic at the University Hospital in Geneva, Switzerland. He says the techniques all have drawbacks — and none of them have been completely validated.
Involved with imaging technology and skin imaging techniques for more than 10 years, Dr. Braun is currently working to correlate the findings of the imaging techniques with actual tumors.
"We do non-invasive imaging, we take the margins provided by the non-invasive imaging and we validate it with histology. We learn the most if the tumor goes further than in the image.
"Once these imaging techniques are validated they will help the surgeons to map the tumor extension prior to surgery and have the potential to considerably reduce the recurrence rate for this type of skin cancer," Dr. Braun says.
At the recent International Skin Cancer Conference in Zurich, Dr. Braun evaluated the potential of various non-invasive techniques currently available.
Autofluorescence is a technique that, for the moment, is only feasible in the laboratory but not in vivo, Dr. Braun says.
"The signal of autofluorescence is weak and requires a complex amplification system so you can see something. For the moment this technique is only feasible in the laboratory but not in practicality."
Optical coherence tomography (OCT) - "There are only few centers that use this because the equipment is so expensive and not user-friendly.
"The problem is that this technique has a limited penetration in the tissue and does not go deep enough. In my opinion, this technique is interesting but still in a research stage," Dr. Braun explains.
"High resolution ultrasound is much less expensive and we can see the tumor extension for up to 15 mm. It's possible to see if it's infiltrating other tissues, Dr. Braun says. However, the drawback is significant.
"The disadvantage is that on curved surfaces, it's very difficult to use because high resolution ultrasound uses a chamber filled with water. Imagine doing that on a nose? There is no way you can keep that chamber waterproof, so I always almost 'drown' my patient when I try to do that," Dr. Braun says.
It's also impossible to mark the edges and to map a tumor prior to surgery with the current system, he adds.
Dermoscopy is very good to make the diagnosis, but does not always show the lateral extensions of the tumor.
"Sometimes there is no difference between normal skin and tumor. For most cases, dermoscopy goes deep enough, but you can have tumor nests that are not pigmented and which, under this method, are indistinguishable from normal skin. You may see some pigmentation, but the tumor can go further than that," Dr. Braun says.
Confocal laser scanning microscopy "This is the most promising as far as what we have experienced so far in a list where every technique has limitations. It has a very small field of view. It allows a very precise correlation in the area you can see, but does not go deep enough for all cases."
Polarized light imaging is new.