Not Your Typical Tonsil: Metastatic Merkel Cell Carcinoma or Primary Disease?

Abstract

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine tumor that almost always presents as a cutaneous lesion in the sun-exposed areas on the bodies of elderly white males. Metastasis to lymph nodes in the presence or absence of a known primary site and occurrence of these tumors in non-sun-exposed sites have also been described; however, an incidence of recurrent disease arising in the palatine tonsil in the absence of any detectable primary lesion has never been reported in the literature. In this report, we discuss a case of a 72-year-old female who was found to have a single axillary lymph node, which was resected and proved to be positive for MCC of unknown primary (MCCUP). Since there was no evidence of additional disease, the patient elected not to pursue adjuvant therapies. Six and a half months later, she presented with a complaint of dysphagia and a right-sided exophytic tonsillar mass. Tonsillectomy revealed MCC with no detectable primary cutaneous lesion. She received adjuvant therapy with avelumab and demonstrated a complete response after one year of bi-weekly treatments. Seven months following cessation of adjuvant treatments, surveillance positron emission tomography (PET) revealed enlarged retroperitoneal, pretracheal, periaortic, and left axillary lymph nodes concerning for recurrence. She elected to forgo additional biopsies and restarted avelumab the following month. She continues to be followed up on a monthly basis.

A rare tonsillar metastasis of Merkel cell carcinoma: A case report

“…13 The five prior reported cases of metastatic MCC to the palatine tonsil are metachronous (7 months to 7 years after presentation) and were all symptomatic. 1 In one study, the authors used microarray-based comparative genomic hybridization to demonstrate that what appeared to be a metachronous metastasis to the tonsil was actually a second primary MCC. 15 In contrast, we report a patient presenting with a synchronous, asymptomatic palatine tonsillar metastasis that was incidentally discovered on staging PET-CT. MCC risk factors include chronic UV-mediated damage to sun-exposed areas of the skin and chronic immunosuppression due to HIV, lymphoma, or organ transplantation.…”

“…Other immunohistochemical staining that are helpful in differential diagnosis include: positive CD99 for primitive neuroectodermal tumor, leukocyte common antigen positive for small‐cell lymphomas and S100, Melan‐A and HMB‐45 positive for malignant melanoma 8 . As a neuroendocrine tumor, neuroendocrine markers such as chromogranin A, synaptophysin, CD56, neuron‐specific enolase usually confirm the diagnosis 1,16 . MCPyV involvement in MCC is demonstrable via tumor staining and serology (80% and 60%, respectively) 8 .…”

“…Metastatic involvement to the tonsil is typically metachronous and generally presents with odynophagia, pharyngitis, dysphagia, and globus 13 . The five prior reported cases of metastatic MCC to the palatine tonsil are metachronous (7 months to 7 years after presentation) and were all symptomatic 1 . In one study, the authors used microarray‐based comparative genomic hybridization to demonstrate that what appeared to be a metachronous metastasis to the tonsil was actually a second primary MCC 15 .…”

“…Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine tumor that commonly presents as cutaneous or mucosal tumor, arising from Merkel mechanoreceptor cells in the skin and in ectoderm‐derived mucosa 1,2 . MCC has been reported to have a rising incidence rate of 95% from 2000 to 2013 3 .…”

“…2,11 Considering all primary tumor types, only about 100 cases of metastases to the palatine tonsil have been documented in the literature, specifically with MCC metastatic to the palatine tonsil comprising of only five of the cases. 1,2 Among the reported cases of metastatic MCC to the palatine tonsil, patients commonly presented with pharyngitis, dysphagia, and other oropharyngeal symptoms, years after wide excision of the primary cutaneous tumor. 1,2,5 We report a case of a 57-year-old female patient who presented with primary MCC of the right buttock, with an incidental, asymptomatic metastasis to the left palatine tonsil.…”