How to Tell the Difference Between Rosacea and BCC?

Finding and evaluating skin lesions in a background of skin can disease can be very difficult. Rosacea on the skin comes in many forms (erythematotelangiectatic, papulo-pustular, glandular) and many people have features of all three forms. Basal cell carcinomas also come in many forms (nodular, superficial, morpheaform, etc). As you can imagine, there can are many features common to both conditions (bumps, blood vessels, location of the conditions, location)

Regular self-exams and regular exams by your dermatologist would be the best way to detect basal cells early. One or two exams are almost never sufficient to scrutinize every lesion. Nor do you want to biopsy every bump and skin thickening that you find, since this can lead to disfigurement. Regular exams will allow you and your doctor to address new lesions and biopsy or re-evalate lesions based on the level of suspicion for cancer. If you find lesions that you are concerned about, bring them to your dermatologist's attention. This will likely be an on-going project for you and your doctor, but a strong collaborative effort will minimize your morbidity. Best of luck.

Sometimes a pimple of rosacea can mimic a BCC, and the other way around.  It is best to be aware of your body and if any new spots develop that do not resolve, or grow rapidly, bleed or become irritated, have them examine by a dermatologist sooner than later. 

It actually sounds like you were right and not wrong to insist on a biopsy.

Usually it is quite easy to tell the difference with the erythematotelangiectatic type of Rosacea. This is the type in which there is a sheet of redness spread across the center of the face, often times with small blood vessels called telangiectasias.A basal cell carcinoma will appear as a pearly, shiny papule or nodule oftentimes with a telangiectasia ( wiry thin blood vessel) perched on its top or emanating from the side. Since this is the type of Rosacea usually found in females, there is not much of a diagnostic challenge.

However, if you have the papulopustular variant, in which there are large pores, knobby bumps, and intermittent pustules, this can be more difficult than it would first appear. The granulomatous type of Rosacea ( roughly a bump from a cluster of lymphocytes, a type of white cell) can be even more of a diagnostic dilemma. Usually a basal cell is a bit more shiny. Growth in a bump would also be indicative of a basal cell. Any sort of ulceration ( hole formation) is an ominous sign.

However, even the most experienced dermatologist may be forced to biopsy one of these lesions to rule out a basal cell.

The fact that you have had two of these lesions, requiring Moh's chemosurgery, will emphasize to all of your physicians, not only your dermatologist, to be en garde.