ZusammenfassungKutane Lymphome präsentieren sich klinisch und histologisch oftmals ungewöhnlich und stellen nicht selten eine diagnostische Herausforderung für den Dermatologen dar. In dieser Arbeit werden die vielgestaltigen Präsentationsformen der Mycosis fungoides und anderer kutaner Lymphome anhand von Fallbeispielen aus der Würzburger Spezialsprechstunde für kutane Lymphome vorgestellt und ein Überblick über die Verwechslungsmöglichkeiten mit anderen Dermatosen gegeben.

We here present the case of a 67-year-old woman with a history of a slowly progressive, polypous nodule on her left wrist. The lesion was excised, and the histological analysis revealed a clear cell tumour that was relatively sharply demarked from the surrounding tissue extending into the subcutaneous tissue. The tumour showed a characteristic trabecular pattern in which the tumour cells were arranged around numerous vessels. The neoplastic cells had a predominantly epithelioid shape, granular eosinophilic to clear cytoplasm and prominent centrally located nucleoli. The histological differential diagnosis included a metastatic clear-cell renal cell carcinoma and a primary cutaneous perivascular epithelioid cell tumour (PEComa). Immunohistochemically, the tumour cells revealed homogenous expression of HMB-45, MiTF and CD10, whereas MART-1 and S100 were negative. Antibodies against actin marked the trabecularly arranged vessels, and the neoplastic cells yielded a patchy positivity against actin and desmin. Additional immunohistochemical stains against pan-cytokeratin, CAIX, PAX-8 and EMA were negative. Based on the morphologic and immunophenotypic findings, the histological diagnosis of a CD10-positive cutaneous PEComa was made.

Anti-PD-1 targeted immunotherapies have revolutionized the treatment of advanced melanoma and other tumor entities, and long disease-free intervals have been reported in responding patients. However, a considerable number of patients still progress rapidly after the start of anti-PD-1 antibodies. Here, we document two patients, 78 and 85-year old, who suffered from advanced BRAF-V600 wild-type melanoma and received pembrolizumab 2 mg/kg every 3 weeks as the first systemic treatment. After only one, respectively, two infusions of pembrolizumab, both patients developed melanuria and diffuse melanosis cutis (DMC) on sun-exposed areas of their skin. Both also had liver metastases, which have been reported to be associated with DMC before. Pembrolizumab was stopped because of rapid tumor progression and both patients died within 2 months after manifestation of DMC. We conclude that DMC is a condition that may be a negative predictor of response to anti-PD-1 treatment. With respect to the very short survival, which is even shorter than that reported after conventional therapies, it needs to be evaluated whether immunotherapy may be a (relative) contraindication in DMC patients when another treatment option, that is targeted therapy, is available.