In two patients with classic Hodgkin's disease and non-Hodgkin's B-cell lymphoma, we identified a common B-cell precursor, probably a germinal-center B-cell, for both lymphomas. This finding suggests that the two types of lymphoma underwent both shared and distinct transforming events and provides proof of the B-cell derivation of Reed-Sternberg cells in classic Hodgkin's disease.

Background: Verrucous carcinoma is a slowly growing, well-differentiated neoplasm with a predilection for the oral cavity. Objective: Data on the association of human papillomavirus (HPV) with oral verrucous carcinoma are very scarce. We searched for the presence of HPV in different stages of the tumour in a patient repeatedly treated by means of surgery, cryotherapy, radiotherapy and chemotherapy over a decade. Methods: HPV DNA was detected in archival tumour tissue by nested PCR. HPV types were identified based on restriction fragment analysis. Results: HPV type 11 was found in 1 early-stage and HPV 16 in 2 late-stage biopsy specimens of the tumour. Conclusion: Our findings provide further evidence for a role of HPV in oral verrucous carcinoma. The case history emphasizes the importance of a joint clinicopathological approach to this tumour.

Dermatofibromas are very common tumors of the skin, but little is known about their etiology and pathogenesis. Current concepts of disease pathogenesis are discussed, with special emphasis on an immunoreactive origin. There is recent evidence, that high numbers of cells with dendritic morphology and positive staining for factor XIIIa are concentrated at the periphery of the lesions. Furthermore, they express MHC class II molecules and costimulatory molecules such as B7-1 and B7-2 on their surface. Thus, there are similarities to professional antigen-presenting cells of the dendritic cell family, so-called dermal dendritic cells (DDCs), which have recently been identified in the human dermis. A concept is developed which explains DF as an abortive immunoreactive process, featuring DDCs as initiators of the disease.

Leg ulcers are a relatively frequent problem in patients with myeloproliferative disorders under treatment with hydroxyurea (HU). The pathogenesis is currently unknown and may be multifactorial. Concomitant arterial or venous disease may play a contributing role in the development of these wounds. Vasculitis, cryoglobulinemia and pyoderma gangrenosum should be considered if typical clinical signs are present. We report on 3 patients with myeloproliferative disorders who developed HU-induced leg ulcers and review the literature. HU-induced leg ulcers share clinical features which can help to differentiate them from leg ulcers of other etiologies: occurrence under long-term treatment with HU at a dose of at least 1 g/day, localization in the malleolar region and spontaneous healing when HU is discontinued. We conclude that differentiation between disease-related and treatment-induced leg ulcers can be difficult and may not always be possible. In HU-induced leg ulcers, cessation of the drug typically leads to wound healing.

Pityriasis rosea (PR) is an acute, inflammatory skin disease of unknown cause. Clinical and experimental findings indicate an infectious etiology of PR. Various infectious agents including viruses have been proposed as causative agents and their presence in PR samples has been extensively investigated. Recently, human herpesvirus 7 was linked to PR, but contradictory findings have been reported by various investigators. Here, we describe the features of PR that suggest an infectious cause and review the data from viral studies in PR reported in the literature. In addition, we present a pathogenetic model of PR which may be helpful in planning and evaluating studies for the search of a putative PR-associated virus. Based on the current state of knowledge, none of the known viruses could, so far, be conclusively associated with PR.