One in a million Monday. Unwittingly saved by the clinician. This case was not a consult, it was just a good old biopsy from a satellite hospital for whose patients we provide pathology diagnostic services. In that hospital, breast surgeons coordinate breast patient care, perform biopsies, discuss treatment and surgical plans with patients, and eventually refer to oncology as needed. Unlike our radiologists and oncologists here at WashU, the surgeons at that hospital do not want to get a tumor diagnosis then get an addendum with the biomarkers. They like to see a complete report all at once. I can't say I dislike that practice, and after this particular case, I like it even more, because it saved me from a major (albeit exceptionally rare) misdiagnosis. The images below depict a tumor I was squarely going to call invasive solid papillary carcinoma because, to my eyes, that's exactly what it looks like. Except that's not what it is. And because I waited for the biomarkers to sign it out, I was fortunate to find out it was triple negative, which would be extremely unusual for solid papillary carcinoma. So, I contacted the surgeon and dug into her chart, and sure enough, the patient had a history of metastatic mucoepidermoid carcinoma of the minor salivary glands. That's when I started seeing a hint of squamous differentiation and possible mucous cells. CK5/6 and p63 were done and were confirmatory. MAML2 FISH was also positive and sealed the deal. I did not find a similar case in the literature. Lessons from this monumental near miss. 1. Clinician preferences did save me this time, but the clinician's omission of pertinent medical history is a common and persistent problem. 2. Always remember that breast biomarkers are not only predicitve and prognostic, but also diagnostic. If their pattern does not fit with the tumor's morphology, take a deep breath and dive into those muddy diagnostic waters. 3. Again and again, be vigilant, look for clinical information, don't make assumptions. Easier said than done, of course, and I do not want to encourage paranoia because I am not the paranoid type, but sharp alertness is one absolute must, and not allowing hasty explanations for things that don't quite fit is another. 4. Morphology is key, but nature loves mimicry. Don't be a hammer. Everything is not a nail. @washupathedu @wusm_pathology #PathTwitter #Breastpath #ENTpath