Merkel Cell Carcinoma With Isolated Pancreatic Metastasis

Merkel cell carcinoma (MCC) is a highly aggressive cutaneous neuroendocrine carcinoma, frequently associated with distant metastasis. However, recurrence of MCC manifesting with only pancreatic involvement is exceedingly rare. A 53-year-old man presented to our institution with abdominal discomfort 3 months after initial resection of chest wall MCC. Imaging revealed lesions in the pancreas and peripancreatic lymph nodes. Pathology obtained through endoscopic ultrasound confirmed recurrence of MCC. He underwent chemotherapy with cisplatin and etoposide, resulting in a complete resolution of the pancreatic lesions. Unfortunately, he passed away from sudden cardiac arrest while being in remission from MCC. Immunohistochemistry is crucial in differentiating MCC from primary pancreatic glandular and neuroendocrine tumors. While there are no definitive guidelines in the management of pancreatic lesions associated with MCC, checkpoint inhibitor immunotherapy is increasingly being used.

Metastatic Merkel Cell Carcinoma Masquerading as Multiple Immune-Related Adverse Events

Merkel cell carcinoma is a rare cutaneous neuroendocrine carcinoma with a high rate of regional and distant metastasis and mortality. Here, we report a novel case of Merkel cell carcinoma which presented as a primary lesion to the left cheek with regional lymph node involvement and was treated with pembrolizumab and radiation. Widely metastatic disease eventually revealed on autopsy clinically mimicked immune-related organ insult leading to management with immunosuppressants. The patient also had a biopsy-confirmed immune-related cutaneous adverse event during admission. The case highlights a rare circumstance in which disease progression masqueraded as multiple immune-related end-organ adverse events. Contribution of on-target anti-PD-1 toxicity remains a possibility.

Update on eighth edition American Joint Committee on Cancer classification for Merkel cell carcinoma and histopathological parameters that determine prognosis

Merkel cell carcinoma (MCC) is a rare primary cutaneous neuroendocrine carcinoma. The annual incidence of MCC is increasing in the USA. Timely diagnosis and proper staging of this tumour are crucial as MCC has high rates of regional recurrence and lymph node and distant metastasis. In this review, we outline the key differences between the tumor node metastasis (TNM) staging criteria for MCC in the seventh and eighth editions of the AJCC Cancer Staging Manual. We also discuss histopathological parameters that are not included in the eighth edition of the manual but have been shown in other studies to predict a worse prognosis in patients with MCC. Correct assessment and reporting of these clinically relevant histopathological parameters is of utmost importance for practising pathologists as management differs according to the stage of the tumour. This review aims to increase awareness of all these parameters, and proper recognition would guide the treating clinicians towards the most appropriate treatment options that can be given to patients.