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To evaluate dermoscopic features and patterns of dermatofibromas using conventional and polarized light dermoscopy. Design: Dermatofibromas were imaged using conventional nonpolarized contact dermoscopy (NPD), polarized contact dermoscopy (PCD), and polarized noncontact dermoscopy, followed by evaluation and comparison of dermoscopic features of the lesions. Setting: Dermatology clinic specializing in pigmented lesions. Patients: Fifty patients with dermatofibromas. Results: The most common features of dermatofibromas observed with NPD and PCD were central white scarlike patches (37 [74%] and 42 [84%], respectively), brown globulelike structures (21 [42%] and 22 [44%]), vascular structures (24 [48%] and 22 [44%]), and a peripheral fine pigmented network (36 [72%] for both). A newly described feature observed with PCD was a central white patch characterized by shiny white streaks. With polarized noncontact dermoscopy, the most characteristic feature was a central pink hue or "vascular blush" (44 [88%]) and visibility of blood vessels (41 [82%]). The most common pattern identified with NPD and PCD was the combination of a peripheral pigmented network and a central white patch in 28 (56%) and 31 (62%) of lesions, respectively. With polarized noncontact dermoscopy, the most common pattern was a central pink hue with a peripheral pigmented network (23 [46%]). There was good to excellent agreement when comparing NPD with PCD images, but there was a variable level of agreement when polarized noncontact dermoscopy images were compared with NPD and PCD images. Conclusions: Conventional and polarized light dermoscopy are not equivalent but may be complementary. This study highlights some salient differences. We were able to identify new dermoscopic features and patterns not previously described with conventional dermoscopy. These new criteria can aid in the diagnosis of dermatofibroma.

RNA-dependent RNA polymerase (RDRP) activity was characterized in a cytoplasmic extract of Kunjin virus-infected Vero cells at 24 hr. The activity was influenced, possibly indirectly, by the length of prior treatment of infected cells with actinomycin D; however, 6 micrograms/ml actinomycin D and 10(-5) M alpha-amanitin in the RDRP assay had no effect. The replication complex was membrane-bound and Mg2+ was essential for RDRP activity. Incorporation was more dependent on exogenous UTP and GTP than ATP or CTP. The specific activity was low, and rate of incorporation of GMP decreased as the period of assay was increased; however, incorporation of label lasted for at least 60 min. RNA products were fractionated by LiCl precipitation, and kinetic studies showed that the sequence of accumulation of label was the same as that observed in vivo, viz., RI----RF----44 S RNA; limited reinitiation was also observed. This sequence of labeling also indicated that the in vitro RDRP activity was due to an enzyme capable of elongation, release, and reinitiation of Kunjin RNA synthesis and not merely end labeling or elongating preexisting RNA molecules. No labeled bands in urea-polyacrylamide gels were observed using extracts from mock-infected cells and hence the three RNA products of assays were readily identified in a single gel. The replication complex was still active after treatment with nonionic detergent, but no labeled 44 S RNA was detected in gels, even in the presence of RNasin in the assay which inhibited some nuclease activity. Antibodies to flavivirus-specific nonstructural proteins were preincubated with infected cell extracts in the presence and absence of detergent but no inhibition of RDRP activity was observed. However, anti-dsRNA plus detergent blocked activity by as much as 78% and label was found only in RF.

Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease) is a systemic proliferation of cells that resemble the sinus histiocytes of lymph nodes. Whereas initial reports highlighted the often striking cervical adenopathy, more than 40% of patients have extranodal involvement. Cutaneous lesions are the most common form of extranodal disease, but cases that present as cutaneous disease without lymph node involvement are rare. We examined biopsies from three patients with cutaneous lesions of sinus histiocytosis, none of whom had detectable systemic involvement, and compared them to those of two patients whose lymph nodes were involved by the disease. The histology of skin lesions in all five cases showed dense nodular or diffuse infiltrates of "histiocytes," emperipolesis of lymphocytes, neutrophils, and plasma cells. "Histiocytes" were present in lumens of dilated lymphatics. At the peripheries of the lesions were lymphoid aggregates and thick-walled vessels surrounded by plasma cells. Staining with anti-S-100 protein antibody showed marked cytoplasmic positivity in the "histiocytes" in each case. The only features that differed among the two groups were the presence of pseudoepitheliomatous hyperplasia and infiltrates of eosinophils in one case in which the disease was limited to the skin. We believe that cutaneous sinus histiocytosis can be specifically diagnosed by skin biopsy. Because cutaneous sinus histiocytosis may be unfamiliar to general pathologists, dermatopathologists, and dermatologists, cases limited to the skin may be under-recognized.