Primary gastric Merkel cell carcinoma harboring DNA polyomavirus: first description of an unusual high-grade neuroendocrine carcinoma

Neuroendocrine neoplasms of the lung and gastrointestinal system: convergent biology and a path to better therapies

Neuroendocrine neoplasms (NENs) can develop in almost any organ and span a spectrum from well-differentiated and indolent neuroendocrine tumours (NETs) to poorly differentiated and highly aggressive neuroendocrine carcinomas (NECs), including small-cell lung cancer (SCLC). These neoplasms are thought to primarily derive from neuroendocrine precursor cells located throughout the body and can also arise through neuroendocrine transdifferentiation of organ-specific epithelial cell types. Hence, NENs constitute a group of tumour types that share key genomic and phenotypic characteristics irrespective of their site of origin, albeit with some organ-specific differences. The establishment of representative preclinical models for several of these disease entities together with analyses of human tumour specimens has provided important insights into crucial aspects of their biology with therapeutic implications. In this Review, we provide a comprehensive overview of the current understanding of NENs of the gastrointestinal system and lung from clinical and biological perspectives. Research on NENs has typically been siloed by the tumour site of origin, and a cross-cutting view might enable advances in one area to accelerate research in others. Therefore, we aim to emphasize that a better understanding of the commonalities and differences of NENs arising in different organs might more effectively inform clinical research to define therapeutic targets and ultimately optimize patient care.

Merkel Cell Carcinoma with Gastric Metastasis, a Rare Presentation: Case Report and Literature Review

INTRODUCTION

Merkel cell carcinoma (MCC) is an infrequent, but highly aggressive neuroendocrine neoplasm of the skin with a propensity for recurrence and metastasis. We report a rare case of gastric metastatic localization of this cancer by focusing on the diagnostic, clinical, and surgical approach to the patient.

CASE REPORT

Clinical presentation begins with a peripheral lymphadenopathy whose immunohistochemical characterization identifies the lymphatic dissemination of the disease. Gradually, the patient develops a severe anaemic state which requires several blood transfusions and surgical gastric resection to remove a large bleeding lesion of the antral region. The histopathological analysis of the specimen confirms the metastatic origin from MCC, but the primitive lesion remains unknown.

DISCUSSION

Since this clinical situation is very rare, we conducted a review of the literature selecting the few cases reported, in order to evaluate the current knowledge on this topic. Metastatic involvement of the stomach from Merkel cell carcinoma is a rare presentation of this disease progression with a frequent delay in formulating the correct diagnosis and in further treatment which may be life-threatening for the patient. As regards the local treatment, there is no specific guideline, and the therapeutic indication should be tailored on the specific case.

Primary Merkel Cell Carcinoma of the Submandibular Gland: When CK20 Status Complicates the Diagnosis

Merkel cell carcinoma is a neuroendocrine tumor that occurs predominantly on the sun-exposed skin, with rare cases in the extracutaneous sites. It represents one of the extremely rare malignant neuroendocrine tumors of the salivary glands. We report a case of primary Merkel cell carcinoma of the right submandibular gland. The preoperative diagnosis was doubtful and the definitive histological diagnosis proved to be very difficult considering the extreme rarity of this tumor. The intraoperative evaluation of the macroscopic characteristics of the lesion led to an elective lymph node dissection. The extreme aggressiveness of the disease has resulted in the necessity of a new post-operative staging and in a multimodal treatment. This is the first primary submandibular gland Merkel cell carcinoma described in the literature. Differential diagnosis may be challenging and proper hematoxylin-eosin staining and immunohistochemical studies are mandatory.