Merkel cell carcinoma presenting as a malignant pleural effusion post‐COVID‐19 hospitalization: A case report and literature review

Abstract

Merkel cell carcinoma (MCC) is a rare, highly aggressive neuroendocrine carcinoma of the skin, associated with immunosuppression, UV light exposure, and the Merkel cell polyomavirus (MCPyV). Cases of metastatic MCC diagnosed in body fluid cytology are extremely rare; only five cases have been reported previously in the English literature. We present a case of a 65-year-old male with acute respiratory failure and an enlarged right pleural effusion. He had two hospitalizations for COVID-19 pneumonia 2 months prior, for which he received steroid treatment and tocilizumab.Emergent thoracentesis was done, with pleural fluid sent for cytologic evaluation.Both the Papanicolaou stained ThinPrep slide and cell block demonstrated clusters of predominantly small to medium sized blue round cells with hyperchromatic nuclei, scant cytoplasm and fine chromatin, in a background of rare mesothelial cells, macrophages and numerous lymphocytes. Tumor cells were positive for CD56, chromogranin, synaptophysin, SAT2B, MCPyV, and CK20 in perinuclear dot like pattern, while negative for TTF-1 and CD45 immunostains. Ki67 proliferative index was approximately 40%. The patient had a history of MCC of the right ulnar forearm 4 years before the current presentation, which was unknown to us at the time of cytologic evaluation. To the best of our knowledge, this is the sixth case of metastatic MCC diagnosed by fluid cytology and the first reported in a patient receiving immunosuppressive treatment for COVID-19. Further reporting of such cases may increase awareness, especially when prior history is not readily available, such as in our case.

Cytology coupled with immunocytochemistry identifies Merkel cell carcinoma: A rare intruder in the cerebrospinal fluid

“…Merkel cell carcinoma shows immunoreactivity for CK20, neuron specific enolase (NSE), CD56, CAM5.2, synaptophysin, chromogranin and the recently described markers anti‐MCPyV large T‐antigen and special AT‐rich sequence binding protein 2 (SATB2) 5 . CK20 is positive in about 95% of cases showing a paranuclear dot‐like pattern, and these paranuclear buttons (unique to MCC) consist of intermediate filaments, as shown by ultrastructural studies 3 .…”

“…Metastasis to body cavity fluids is associated with a very poor prognosis. Metastatic MCC has rarely been reported in body cavity effusions 5–7 . Metastasis involving the cerebrospinal fluid (CSF) is extremely rare, with only isolated case reports found in the literature 8–10 .…”

Higher Frequency and Poor Prognosis with COVID-19 Associated Cytokine Storm among Cancer Patients: Between Two Fires

“…Tocilizumab treatment was also reported to be efficient for patients with malignancy and severe COVID-19 in several cases. In the Table, we summarized the available reports of patients with malignancy and severe COVID-19 treated with tocilizumab and/or anakinra [52,[66][67][68][69][70][71][72]. These findings were not surprising considering the role of IL-6 both in oncogenesis and COVID-19-associated cytokine storm and could be interpreted as the dominance of IL-6 in the inflammatory milieu of these patients.…”

“…The safety and efficacy of anakinra were established in patients with secondary HLH due to rheumatological conditions, cancer and infection both in adults and children [15,83,84]. The short half-life (4-6 hours) of anakinra also has the advantage of rapid withdrawal in case of infections or other complications in critically ill patients [67].…”

A review on the oncogenesis of Merkel cell carcinoma: Several subsets arise from different stages of differentiation of stem cell

“…CK20 is a low-molecular-weight cytokeratin normally expressed in the gastrointestinal epithelium, urothelium, Merkel cells, and MCCs, the latter with a distinctive perinuclear dot-like pattern. [ 9 , 10 ] CK7 and TTF-1 are commonly used to exclude metastasis from small cell lung carcinoma.…”