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Along with collagen, elastic fibers are integral components of cutaneous connective tissue. A decrease in elastic fibers or loss thereof has been described in a number of clinically distinct skin diseases, both hereditary and acquired. In disorders associated with inflammation, elastophagocytosis is an important histological hallmark. Treatment is generally difficult., (© 2018 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.)

Background: Lymphoplasmacytic plaque (LPP) is a recently described rare skin disease characterized by a dense dermal lymphohistiocytic infiltrate with polyclonal plasma cells. The clinical picture is distinct with reddish to brownish plaque with a predilection for the lower leg. LPP typically affects children., Objective: To define clinical and histologic criteria of LPP and to develop a diagnostic flow chart., Methods: We investigated six of our own LPP cases. Immunoglobulin light chains, IgG, IgG4, CD31, CD163 as a histiocytic marker were examined by immunohistochemistry. PCR-based molecular studies were conducted for borrelia sp., mycobacterial and leishmania sp. Moreover, 10 cases, which have been reported in the literature, were checked for the same features., Results: We could differentiate three main histological patterns (superficial band-like only, [deep] dermal only and mixed). Acanthosis and interface dermatitis are key features in cases with a superficial band-like or mixed infiltrate. Granulomas and giant cells could be only found in about 30% of the cases. The number of plasma cells was variable accounting for 5-40% of the infiltrate. The number of blood vessels was increased in the majority of the cases. 'Free-floating' collagen bundles surrounded by histiocytes (pseudorosettes) were identified as a new histological feature. An infectious agent could be excluded in all cases., Conclusions: LPP is a long-standing skin disease, which may also occur in adults and in other body regions than the lower leg. Reproducible clinical and histological criteria allow delineating a diagnostic work-up for LPP., (© 2015 European Academy of Dermatology and Venereology.)

Granulomatous disorders affecting the skin belong to a heterogeneous group of diseases. With the exception of granulomas induced by infectious agents or foreign bodies, the etiopathogenesis of granulomatous disorders is still poorly understood. The knowledge of histopathologic changes is of great importance for understanding clinical presentation and disease course., (© 2015 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.)

Keratoacanthomas represent epithelial tumors which are characterized by a keratin-filled crater, rapid growth in the proliferation stage, and the potential for spontaneous regression. Histologically, keratoacanthomas display distinct features which must be differentiated from squamous cell carcinomas in the proliferation stage and fully developed tumors and in the regression stage the differential diagnosis of verruca vulgaris must also be considered.

Nevus sebaceus is a hamartoma that is frequently associated with various neoplasms. Among the neoplasms observed in sebaceus nevi, trichoblastomas are the most common. The present case, to my knowledge, is the first description of a clear cell variant of trichoblastoma.

Calciphylaxis is a rare syndrome mostly affecting patients with secondary hyperparathyroidism and in some cases with functional protein C or protein S deficiency. Skin lesions begin as superficial painful patches that progress to deep necrotic lesions. The findings are often misdiagnosed as livedo vasculitis and the prognosis is poor. Histopathologically, calcification in the media of small arteries and arterioles with intimal hyperplasia is seen. It is unclear if this morphologic hallmark is pathogenetic. Therapeutically, the calcium-phosphate product should be lowered pharmacologically by an intensified and modified dialysis treatment and parathyroidectomy.

Antibodies against HMB-45 antigen are widely used in the immunohistochemical investigation of melanocytic tumours as a marker of activation. While malignant transformation is one explanation for HMB-45 expression, we searched for other factors by investigating 252 biopsies of non-melanocytic skin lesions with 21 different diagnoses for the presence of HMB-45, using both single and double staining techniques. Epidermal melanocytes in lesions with an increased epithelial proliferation-either neoplastic or reactive-and lesions with a prominent vasculature showed an enhanced expression of HMB-45. The results indicate that the presence of HMB-45 is not only influenced by primary melanocytic changes but also may be dependent on epithelial proliferation and vascular factors. These mechanisms should be considered when interpreting HMB-45 staining of melanocytic lesions.

With the increasing use of immunohistological techniques in the diagnosis of skin diseases, the question of appropriate techniques becomes more and more important. In this study the ABC (avidin-biotin-peroxidase-complex)-technique, the IGSS (immunogold-silver-staining)-technique and the APAAP (alkaline phosphatase anti-alkaline phosphatase)-technique are described. Antigenic determinants are demonstrated in frozen and paraffin-embedded sections with monoclonal and polyclonal antibodies, lectins and protein A. Sensitivity, reliability, application and handling of these techniques and their suitability for double labelling are compared. The ABC-technique is easy to handle, as sensitive as the other techniques, and gives good results with mono- and polyclonal antibodies, lectins and protein A in paraffin-embedded sections. The APAAP-technique yields good results when monoclonal antibodies are used in frozen sections. Similar results are obtained with the IGSS-technique, which also gives good results with polyclonal antibodies, lectins and protein A.