Dermatopathology - Current status and development in German-speaking dermatology.

Dermatopathology has been an integral part of dermatology for more than 100 years and is essential for high quality patient care. In German-speaking countries, dermatologists can acquire an additional qualification in dermatopathology after appropriate further training. For many years, dermatopathological diagnostics has advanced far beyond morphology. Immunohistochemistry and molecular pathology are nowadays an essential part and a prerequisite for the preservation of our discipline. Due to the increasing implementation of digitalization and artificial intelligence, dermatopathology is forward-looking and offers an attractive working environment for young colleagues. Dermatopathology is also indispensable for research, and this fact should also be taken into account by creating academic positions and professorships in the future.

[Acquired progressive lymphangioma in a 13-year-old boy]. / Erworbenes progressives Lymphangiom bei einem 13­jährigen Jungen.

Acquired tumors of lymphatic vessels are rare. Clinically, progressive lymphangioma usually appears as circumscribed plaques of small to medium size. In contrast, our case of a 13-year-old boy demonstrates a case of progressive lymphangioma with a solitary large indurated plaque. No extracutaneous manifestation was found. Systemic therapy with corticosteroids and methotrexate resulted in an improvement of the patient's condition. Dependent on clinical course and appearance of the disease, therapy with mTOR inhibitors may be considered as a therapeutic option.

Stage-related PD-L1 expression in Kaposi sarcoma tumor microenvironment.

BACKGROUND: The immune checkpoint molecule PD-L1 represents an important target in oncological immune therapy. The aim of our study was to evaluate PD-L1 expression and the composition of the tumor microenvironment (TME) in Kaposi sarcoma. METHODS: Immunohistochemical stains were performed for PD-L1, CD3, CD33, CD68, and CD168 in 24 Kaposi sarcoma samples. In PD-L1-positive cases, the double stains for PD-L1, CD31, podoplanin, and HHV8 were added. RESULTS: PD-L1 was observed in 71% of the samples and was predominantly located in the TME. PD-L1 expression was significantly higher in nodular stage than in patch/plaque stage. The TME consisted of CD68+/CD163+ macrophages, CD33+ myloid-derived suppressor cells and monocytes and CD3+ T-cells. The TME showed a peritumoral distribution in nodular stage, in contrast to a diffuse distribution in patch/plaque stage. In 12 samples (50%), no plasma cells were found. CONCLUSION: In nodular stage of KS, the TME is pushed back in the periphery of the tumor nodules. The PD-L1-positive TME between the tumor cells might protect them from the immune attack. An anti-PD-L1 treatment might be promising in KS patients.

S2k Guidelines for Cutaneous Basal Cell Carcinoma - Part 2: Treatment, Prevention and Follow-up.

Basal cell carcinoma (BCC) is the most common malignant tumor among fair-skinned individuals, and its incidence had been steadily rising in the past decades. In order to maintain the highest quality of patient care possible, the German S2k guidelines were updated following a systematic literature search and with the participation of all professional societies and associations involved in the management of the disease. Part 2 addresses issues such as proper risk stratification, the various therapeutic approaches, and prevention as well as follow-up of patients with basal cell carcinoma.

S2k Guidelines for Cutaneous Basal Cell Carcinoma - Part 1: Epidemiology, Genetics and Diagnosis.

Basal cell carcinoma is the most common malignant tumor among fair-skinned individuals, and its incidence has been rising steadily in the past decades. In order to maintain the highest quality of patient care possible, the German S2k guidelines were updated following a systematic literature search and with the participation of all professional societies and associations involved in the management of the disease. Part 1 highlights new developments in genetics in particular as well as aspects regarding epidemiology, diagnosis, and histology.

Deceptively bland cutaneous angiosarcoma on the nose mimicking hemangioma-A clinicopathologic and immunohistochemical analysis.

BACKGROUND: We investigated 2 cases of deceptively bland cutaneous angiosarcoma (AS), which showed a uniform clinical presentation with a rapidly growing tumor on the nose. It remains unclear whether this was a primary cutaneous manifestation or a metastasis. Both tumors initially presented a high histologic overlap with a benign vascular tumor. The diagnosis was primarily based on the rapidly progressing clinical course and on the results of the staging procedures. METHODS: Immunohistochemical stains were performed for cytokeratin (AE1/AE3 and MNF116), CD31, ERG, CD34 (HPCA1/my10), D2-40/podoplanin, LYVE-1, Ki67, PHH3, αSMA (1A4), MYC, FOS-B, CAMTA-1, TFE-3, WT1, nestin, VEGFR-2(KDR), VEGFR-3(FLT4), HHV8. MYC amplification was also investigated by fluorescence in situ hybridization. RESULTS: The tumor cells were negative for MYC and revealed no D2-40/podoplanin expression. SMA-positive pericytes formed rims around the vessel. The proliferative activity (Ki-67) was elevated, in one case only in a later stage. DISCUSSION: Cutaneous ASs can be rather bland and may easily be mistaken for benign vascular tumors. Both cases presented a uniform clinical picture, which implied a malignant vascular tumor. In contrast, the cytomorphology of the endothelial cells and the immunohistochemical profile were not suspicious. We worked out subtle histological criteria, which should allow an early detection of such tumors.

Cutaneous disorders characterized by elastolysis or loss of elastic tissue.

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.

Elastolysen und Hauterkrankungen mit Verlust der elastischen Fasern.

Die elastischen Fasern sind neben den kollagenen Fasern der wichtigste Bestandteil des Bindegewebsgerüstes der Haut. Eine Verminderung oder ein Verlust der elastischen Fasern ist bei einer Vielzahl von klinisch sich unterschiedlich präsentierenden Erkrankungen, hereditär oder erworben, beschrieben. Bei den Erkrankungen, die mit einer Entzündung einhergehen ist die Elastophagozytose ein wichtiges histologisches Merkmal. Die Therapie der Erkrankungen dieser Gruppe ist grundsätzlich schwierig.

PD-1 and PD-L1 in neoplastic cells and the tumor microenvironment of Merkel cell carcinoma.

BACKGROUND: Merkel cell carcinoma (MCC) is an aggressive neoplasm, which is often associated with Merkel cell polyomavirus (MCPyV). Programmed death-1 (PD-1) and its ligand PD-L1 are key players of the tumor microenvironment (TME). METHODS: Fourteen paraffin-embedded tissue samples of MCC were stratified by their MCPyV detection. Apart from PD-L1 and PD-1, the TME was further characterized for the expression of CD33, FOXP3 and MxA. RESULTS: We observed PD-1 in 2 of 12 tumors. PD-L1 expression by tumor cells was found in 7 of 8 MCPyV(+) samples and was detected particularly in the periphery. The tumor cells were surrounded by a shield of PD-L1/CD33 immune cells. Expression of PD-L1 by the tumor cells was higher in areas with a denser immune infiltrate. CD33(+) cells without direct tumor contact were PD-L1 negative. Only a low number of FOXP3(+) regulatory T-cells was admixed. Tumor cells of MCPyV(-) samples were mostly PD-L1 negative. CONCLUSIONS: Our data demonstrate that PD-L1 expression occurs in tumor and immune cells, in areas in which they are close in contact. Interferon seems to play a role in this interaction. We postulate that PD-L1(+)/CD33(+) cells shield the tumor against attacking PD-1(+) immune cells. Therefore, next to anti-PD-1/PD-L1 antibodies, blockade of CD33 seems to be a promising therapeutic approach.

Histologic features of granulomatous skin diseases.

Granulomatous disorders affecting the skin belong to a heterogeneous group of diseases, which were predominantly classified based on pathogenetic features. In infections diseases a granuloma is formed if an agent could not be eliminated by the immune system. Typical agents which cause granulomatous reactions are mycobacteria, fungal infections, especially extra European agent, which could effect the skin by, dissemination (e.g. histoplasmosis) or parasites, like leishmaniasis.

Mitotic rate in primary melanoma: interobserver and intraobserver reliability, analyzed using H&E sections and immunohistochemistry.

BACKGROUND: In 2009, the AJCC issued a revised melanoma staging system. In addition to tumor thickness and ulceration, the mitotic rate was introduced as the third major prognostic parameter for the classification of primary cutaneous melanoma. Given that, according to the 2009 AJCC classification, the detection of one or more dermal tumor mitoses leads to an upstaging - from stage Ia to Ib - of melanomas with a tumor thickness of ≤ 1.0 mm, we set out to investigate the reproducibility of this new parameter. METHODS: In order to assess interobserver reliability, 17 dermatopathologists und pathologists - all well versed in the diagnosis of cutaneous melanoma - analyzed the mitotic rate in 15 thin primary cutaneous melanomas (mean tumor thickness 0.91 mm) using identical slides. Mitotic rates were determined on H&E and phosphohistone H3 (Ser10)-stained samples. Without knowledge of their previous assessment, five of the aforementioned examiners reevaluated the samples after more than one year in order to ascertain intraobserver reliability. RESULTS: Interobserver reliability of the mitotic rate in thin primary melanomas is disappointing and independent of whether H&E or immunohistochemically stained samples are used (kappa value: 0.088 [H&E], 0.154 [IH], respectively). Kappa values improved to 0.345 (H&E) and 0.403 (IH) when using a cutoff of 0/1 vs. 2+ mitoses. Similarly unsatisfactory, kappa values for intraobserver reliability ranged from 0.18 and 0.348, depending on the individual examiner. DISCUSSION: Given the unsatisfactory reproducibility and large variations in assessing the mitotic rate, it remains a matter of debate whether this diagnostic parameter should play a role in therapeutic decisions.

Mitoserate beim primären Melanom: Interobserver- und Intraobserver-Reproduzierbarkeit am HE-Schnitt und in der Immunhistologie.

HINTERGRUND: Die Melanomklassifikation wurde 2009 durch die AJCC revidiert. Für die Klassifizierung primärer Melanome wurde als dritte Größe neben Tumordicke und Ulzeration die Angabe der Mitoserate neu eingeführt. Gemäß der AJCC-2009-Klassifikation des Melanoms führt der Nachweis nur einer oder mehrerer dermaler Tumormitosen bei Melanomen ≤ 1,0 mm Tumordicke zu einer Umgruppierung des Tumors von T1a nach T1b. Dies erklärt, wie wichtig die Frage nach der Reproduzierbarkeit dieses neuen Parameters ist. METHODEN: Zur Prüfung der Interobserver-Reproduzierbarkeit der Mitoserate haben 17 Dermatopathologen und Pathologen, die in der Befundung des kutanen Melanoms sehr erfahren sind, die Mitoserate in 15 dünnen Melanomen mit einer mittleren Tumordicke von 0,91 mm an demselben Tumorschnitt bestimmt. Die Mitoserate wurde am HE-Schnitt und immunhistologisch (IH) mittels des mitosespezifischen Antikörpers Phospho-Histon-H3 (Ser10) bestimmt. Fünf Befunder wiederholten die Bestimmung nach mehr als einem Jahr ohne Kenntnis ihres Vorbefundes zur Ermittlung der Intraobserver-Reproduzierbarkeit. ERGEBNISSE: Die Interobserver-Reproduzierbarkeit der Mitoserate bei dünnen Melanomen ist unbefriedigend und unabhängig davon, ob die Mitoserate am HE-Schnitt oder am immungefärbten Schnitt bestimmt wird (κ-Werte: 0,088 [HE] bzw. 0,154 [IH]). Bei einer Diskriminationsschwelle von 0/1 vs. 2+ Mitosen verbesserte sich der κ-Wert auf 0,345 (HE) bzw. 0,403 (IH). Die Intraobserver-Reproduzierbarkeit lag mit κ-Werten zwischen 0,18 und 0,348 je nach Befunder ebenfalls im unbefriedigenden Bereich. DISKUSSION: Wegen der unbefriedigenden Reproduzierbarkeit und der großen Variation der Befunde zur Mitoserate bleibt es zweifelhaft, ob dieser Befund als Grundlage für Therapieentscheidungen herangezogen werden kann.