Browse the corpus

©2013 UpToDate ® Print Email Histologic features of atypical Spitz tumors Architecture • Diameter usually >5 and often >10 mm • Involvement of the subcutaneous tissue • Ulceration • Poor circumscription • Extensive pagetoid scatter • Effacement of the epidermis • Prominent confluence of melanocytes • High cellular density • Lack of zonation and maturation • Asymmetry • Absent or few eosinophilic hyaline globules (Kamino bodies) Proliferation • Significant mitotic rate (2 to 6/mm 2 ) (particularly >6/mm 2 ) • Deep or marginal dermal mitoses • Proliferative index (Ki-67 expression) - Between 2 to 10 percent [1] - ≥10 to 15 percent [2] Cytology • Granular versus ground glass cytoplasm • High nuclear to cytoplasmic ratio • Loss of delicate or dispersed chromatin pattern • Thickening of nuclear membranes • Hyperchromatism • Large nucleoli References: Vollmer RT. Use of Bayes rule and MIB-1 proliferation index to discriminate Spitz nevus from malignant melanoma. Am J Clin Pathol 2004; 122:499. Kapur P, Selim MA, Roy LC, et al. Spitz nevi and atypical Spitz nevi/tumors: a histologic and immunohistochemical analysis. Mod Pathol 2005; 18:197. Reprinted by permission from Macmillan Publishers Ltd: Modern Pathology. Barnhill RL. The Spitzoid lesion: Rethinking spitz tumors, atypical variants, 'Spitzoid melanoma' and risk assessment. Mod Pathol 2006; 19 Suppl 2:S21. Copyright © 2006.