RT Journal Article SR Electronic T1 Ultrastructural and immunomorphologic study of perinuclear filaments in Merkel cell tumors JF Cleveland Clinic Journal of Medicine JO Cleve Clin J Med FD Cleveland Clinic SP 103 OP 110 VO 52 IS 1 A2 William R. Hart A1 James T. McMahon A1 Raymond R. Tubbs A1 Wilma F. Bergfeld A1 Ronald G. Wheeland A1 Philip L. Bailin YR 1985 UL http://www.ccjm.org/content/52/1/103.abstract AB Two cases of cutaneous small-cell tumor in patients without overt lung disease are presented. Histologic and ultrastructural findings support the diagnosis of Merkel cell tumor. Immunohistochemistry and immunoelectron microscopy demonstrate distinctive perinuclear keratin filaments that may be of histologic significance in separating a Merkel cell tumor from other nonendocrine tumors. A possible mechanism for the formation of perinuclear filamentous whorls is discussed.