[Merkel cell carcinoma. Clinical and histological differential diagnosis, diagnostic approach and therapy]. / Merkel-Zell-Karzinom. Klinische und histologische Differenzialdiagnose, Diagnostik und Therapie.

Merkel cell carcinomas are rare tumors of the skin with an aggressive behavior and frequent regional and distant metastases. Typically, the primary is a fast-growing, painless, reddish nodule with an iceberg-like effect, broadening in the depth. On the trunk and the buttocks, deep clinically rather inconspicuous nodules can occur. The clinical differential diagnosis of the Merkel cell carcinoma includes skin metastases, malignant lymphomas, malignant adnexal tumors and cysts when the tumor is located deep in the soft tissue (e.g. on the buttocks). Histological and immunohistochemical analysis is necessary for the diagnosis. The demonstration of cytokeratin 20 in the typical globular distribution pattern is of main importance in the diagnosis of Merkel cell carcinoma. Because they are very rare, Merkel cell carcinomas are infrequently diagnosed clinically, in spite of the rather characteristic picture. Diagnostic excision with a safety margin of 3 cm is recommended followed by an adjuvant radiotherapy. The radiation field should include the area of the draining vessels and the first regional lymph nodes. There are some reports concerning the advantage of sentinel lymph node biopsy. In distant metastases, the therapy is multimodal and palliative including surgery, radiation and chemotherapy. Because of the high incidence of regional and distant metastases, regular follow-up is important.

[Heinrich Köbner and the "isomorphic phenomenon". History and review of the literature]. / Heinrich Köbner und der "isomorphe Reizeffekt". Geschichte und Uberblick.

The isomorphic phenomenon belongs to the probably most well-known entities of dermatology and is closely connected to the man who was the first to describe it. Today the Koebner phenomenon is well documented in a number of skin diseases and still of considerable interest. Heinrich Koebner first reported his observation in 1872 and caused considerable diverse discussion about the origin of psoriasis in the following years. Heinrich Koebner is not only well known as "father" of the Koebner phenomenon, but also as a founder of the university dermatology clinic and pioneer of dermatology in Breslau. We not only describe the life of Heinrich Koebner, but also discuss the evolution of the term "Koebner phenomenon" and its current status.

Drug-induced Sweet's syndrome in acne caused by different tetracyclines: case report and review of the literature.

Sweet's syndrome was first described in 1964. It is characterized by an acute onset of non-pruritic, painful reddish nodules on the head and neck, chest and/or the upper limbs, mostly accompanied by fever, general malaise and leucocytosis. Histopathological examination shows a diffuse dermal neutrophilic infiltrate. The pathogenesis is still not fully understood, and different diseases have been shown to be associated with this syndrome. However, although still very rare, there is an increase of reports on Sweet's syndrome induced by drugs. We describe a 30-year-old man who experienced acute neutrophilic dermatosis after systemic treatment with minocycline. Additionally, there is a strong possibility that the same patient developed a drug-induced Sweet's syndrome after oral administration of tetracycline and doxycycline.