Summary
Merkel cell carcinoma (MCC, ICD‐O M8247 / 3) is a rare malignant primary skin tumor with epithelial and neuroendocrine differentiation. The neoplastic cells share many morphological, immunohistochemical and ultrastructural characteristics with Merkel cells of the skin. The diagnosis of MCC is rarely made on clinical grounds. Histological and immunohistochemical studies are usually required to confirm the clinical suspicion. Given the frequent occurrence of occult lymph node metastasis, sentinel lymph node biopsy should be performed once distant metastasis has been ruled out by cross‐sectional imaging. Primary tumors without evidence of organ metastases are treated with complete surgical excision with appropriate surgical margins. Radiation therapy should be considered at all stages of the disease.
For advanced MCC that is no longer amenable to curative treatment by surgery or radiation therapy, there is currently no established systemic therapy for which an improvement in recurrence‐free survival or overall survival has been demonstrated in a prospective randomized trial. However, immunotherapy using PD‐1/PD‐L1 blockade seems to be superior to chemotherapy.
Various factors warrant that further diagnostic and therapeutic interventions be determined by an interdisciplinary tumor board. These factors include the tumor's aggressiveness, the frequent indication for sentinel lymph node biopsy along with the frequent occurrence in the head and neck region, the potential indication for adjuvant radiation therapy as well as the complexity of the required diagnostic workup.
An increasing number of patients undergoing radiotherapy (RT) have cardiac implantable electronic devices [CIEDs, cardiac pacemakers (PMs) and implanted cardioverters/defibrillators (ICDs)]. Ionizing radiation can cause latent and permanent damage to CIEDs, which may result in loss of function in patients with asystole or ventricular fibrillation. Reviewing the current literature, the interdisciplinary German guideline (DEGRO/DGK) was developed reflecting patient risk according to type of CIED, cardiac condition, and estimated radiation dose to the CIED. Planning for RT should consider the CIED specifications as well as patient-related characteristics (pacing-dependent, previous ventricular tachycardia/fibrillation). Antitachyarrhythmia therapy should be suspended in patients with ICDs, who should be under electrocardiographic monitoring with an external defibrillator on stand-by. The beam energy should be limited to 6 (to 10) MV CIEDs should never be located in the beam, and the cumulative scatter radiation dose should be limited to 2 Gy. Personnel must be able to respond adequately in the case of a cardiac emergency and initiate basic life support, while an emergency team capable of advanced life support should be available within 5 min. CIEDs need to be interrogated 1, 3, and 6 months after the last RT due to the risk of latent damage.
Zusammenfassung
Das Merkelzellkarzinom (MCC, ICD‐O M8247/3) ist ein seltener, maligner, primärer Hauttumor mit epithelialer und neuroendokriner Differenzierung. Die Tumorzellen teilen viele morphologische, immunhistochemische und ultrastrukturelle Eigenschaften mit den Merkelzellen der Haut.
Die Diagnose MCC wird selten klinisch gestellt. Erst histologisch und immunhistochemisch wird der Verdacht auf ein MCC bestätigt. Nachdem eine Fernmetastasierung durch Bildgebung mit Schnittbildverfahren ausgeschlossen worden ist, sollte aufgrund der hohen Zahl von okkulten Lymphknotenmetastasen eine Schildwächterlymphknotenbiopsie erfolgen. Bei Primärtumoren ohne Hinweise auf das Vorliegen von Organmetastasen soll eine vollständige chirurgische Exzision mit Sicherheitsabstand erfolgen. Die strahlentherapeutische Behandlung sollte in allen Stadien der Tumorerkrankung in Betracht gezogen werden.
Für das fortgeschrittene, operative oder strahlentherapeutische nicht mehr kurativ behandelbare MCC gibt es bisher keine etablierte systemische Therapie, für die in einer prospektiv‐randomisierten Studie eine Verbesserung des rezidivfreien Überlebens oder des Gesamtüberlebens demonstriert werden konnte. Eine Immuntherapie mittels PD‐1/PD‐L1‐Blockade erscheint aber einer Chemotherapie überlegen zu sein.
Aufgrund seiner Aggressivität, der in der Regel gegebenen Indikation zur Schildwächterlymphknotenbiopsie bei gleichzeitig häufiger Lokalisation im Kopf‐Hals‐Bereich, der zu evaluierenden Indikation einer adjuvanten Radiotherapie sowie der Komplexität der notwendigen Diagnostik zur korrekten Prognoseabschätzung soll das Vorgehen im Rahmen einer interdisziplinären Zusammenarbeit (interdisziplinäres Tumorboard) festgelegt werden.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.