FIGURE 1

Case 1 (a–c). Sections from the umbilical skin biopsy (a) show a dense dermal proliferation of mononuclear cells with immature chromatin surrounded by edematous stroma. Epidermis is spared (H&E, 10). Frequent mitotic figures were noted at high power (b, H&E, 400). Representative nuclei from case 1 hybridized with dual color, dual fusion PML / RARA translocation probe. The two fusion signals indicate the fusion products PML / RARA and RARA / PML, while the separate red and green signals represent nonrearranged loci (c). Case 2 (d–f). Scrotal biopsy sections show a dense dermal infiltrate extending into the overlying epidermis (d, H&E, 10). The infiltrate consists of segmented neutrophils admixed with a population of immature cells containing bilobed forms (inset) (e, H&E, 400). Representative nuclei from case 2 illustrating the 1R1G2F signal pattern indicative of t(15;17) (f). Case 3 (g–i). Sections from a scalp biopsy show a perivascular infiltrate extending deep into the dermis (g, H&E, 10). The cells contain abundant cytoplasm with eosinophilic granules. Nuclei are convoluted with occasional bilobed forms with fine chromatin and nucleoli (h, H&E, 400). FISH results were 16% positive for the 1R1G2F signal pattern indicative of t(15;17) as shown in representative nuclei (i). Case 4 (j–l). Skin sections from an abdominal nodule show a deep diffuse dermal infiltrate which spares the epidermis (j, H&E, 10). Nuclei are large with fine chromatin and 1–2 small, distinct nucleoli with occasional irregular nuclear contours and frequent mitoses (k, H&E, 400). A positive FISH signal pattern is illustrated with representative nuclei from case 4 (l).