Merkel Cell Carcinoma

This one was, as one playa confirmed, very hard.  This was one of my patients at Wilford Hall, and he had, as described, a rapidly growing painless nodule with a slight pinkness to it.  It was, as you see, fairly close to skin colored, as have been roughly half of the Merkels I have run across, and it had the consistency of a firm cyst, but it was not rock hard.  The differential was pretty straightforward:  metastatic disease versus Merkel Cell Carcinoma.  The path was consistent with "trabecular cell tumor" and as a result I gave the dermatopathologist a hard time for speaking in paleodermatologic terms.  

Your clues (use all available clues!!) were the patient's age, the location (an admittedly soft call), the history of rapid growth, the appearance of the lesion itself as above, but most importantly, you should have honed in on the fact that an incisional biopsy was performed, and it was a big incision.  Why would we do that???  Because we wanted a lot of tumor with which to work, in case it was a weird met.  It wasn't.