A Comparison of the Histopathologic Growth Patterns Between Non–Merkel Cell Small Round Blue Cell Tumors and Merkel Cell Carcinoma

Background: Merkel cell carcinoma (MCC) is a rare neuroendocrine cutaneous malignancy that shares cytologic, histopathologic, and immunohistochemical features with other small round blue cell (SRBC) tumors. Although the trabecular pattern is anecdotally associated with MCC, objective data are lacking. Methods: This was a retrospective institutional review board–approved observational study conducted on microscopic images of 79 MCCs and 74 other...