Merkel Cell Carcinoma: A Case Of Metastasis to the Tonsils
Overview
Tonsillar metastases of Merkel cell carcinoma (MCC) are very rare. There are as few as five documented and published cases. In this report, we present a case of palatine tonsillar Merkel cell carcinoma metastases in a patient who did not show oropharyngeal symptoms at presentation which is not typical of previous cases that have been previously reported.
Introduction
Merkel Cell Carcinoma
Merkel cell carcinoma (MCC) is a neuroendocrine tumor originating from some specialized skin cells. It is a rare and aggressive condition that commonly presents as mucosal or cutaneous lesions, emanating from the ectoderm-derived mucosa and Merkel mechanoreceptor cells in the skin. Merkel cell carcinoma has been observed to have a 95% increase in its rate of incidence over the space of 13 years (from years 2000 to 2013). The overall survival rate of stage I-III Merkle cell carcinoma ranges from 30% to 75% despite the measures for early detection and adequate management via adjuvant radiotherapy and surgery.
A virus known as the Merkel cell polyomavirus (MCPyV) was seen in 80% of cases to be associated with the development of Merkel cell carcinoma. The remaining 20% of Merkel cell carcinoma cases were reported to be associated with chronic ultraviolet ray(UV)-mediated damage which is common among people aged over 50 years.
Studies have shown that the areas of the body which are frequently affected by Merkel cell carcinoma includes the mucous membranes (4.5%), arms and legs (10%), trunk (30%) and the head and neck region (50%).
Localized skin disease may be seen in 65%-70% of patients suffering from Merkel cell carcinoma, regional lymphadenopathy may be seen in 25% of patients suffering from Merkel cell carcinoma, while distant metastasis occur in 5%-8% of patients suffering from Merkel cell carcinoma with common sites of metastasis being the lung, liver, bone and brain.
Adults were more likely than children to have Merkel cell polyomavirus (MCPyV) load which is detectable using the polymerase chain reaction tests on the specimens obtained from an elective tonsillectomy. In spite of this, metastasis of the tumor to the oral cavity is not common with the occurrence of palatine tonsillar metastases being extremely rare.
An estimate of 100 cases of Merkle cell carcinoma metastases were reported in published literature out of all the cases of Merkle cell carcinoma with only 5 of them being palatine tonsillar metastasis.
Oropharyngeal symptoms such as pharyngitis and dysphagia were reported as common presentations of the patients with palatine tonsillar metastasis of Merklet5 cell carcinoma several years after wide excision of the cutaneous tumor.
In this study, we report a case of a female patient who is 57 years of age that presented with primary Merkle cell carcinoma located at the right buttock with asymptomatic metastasis noted incidentally to the left palatine tonsil.
Case Presentation
A female patient who is 57 years of age presented with an enlarging right buttock mass of 3 years duration. There was a history of minor trauma to the right buttock, however, the mass was associated with pain. The patient is otherwise healthy.
On physical examination, a cutaneous mass measuring 12 by 8 cm was seen on the right buttock and a non-tender, firm mass on the right inguinal area. Computed tomography (CT) with IV contrast scan of the pelvis done before referral revealed a lobulated mass measuring 8cm on the right buttock and multiple lymphadenopathy of the right inguinal lymph nodes.
Neuroendocrine carcinoma was demonstrated via a core needle biopsy of the right buttock mass and a fine needle aspirate of the mass in the right inguinal region.
A positive result for CK20, EMA, chromogranin and Merkel cell polyomavirus (MCPyV) was recorded, while a negative result was reported for CK7 and thyroid transcription factor-1 (TTF-1) on immunohistochemical staining of the biopsy specimen gotten from the right buttock. These investigational findings were consistent with Merkle cell carcinoma diagnosis. Further testing of the Merkel cell polyomavirus oncoprotein antibody was done which revealed an antibody titer of 115,000 SU.
Fused fluorodeoxyglucose-18 positron emission tomography (PET)-CT scan was used at our institution which showed an asymmetric uptake in the left tonsil region which is significant for inflammatory processes or malignancy.
The patient did not report any oropharyngeal symptoms, however, a firm left tonsil was discovered on oral examination. There was no palpable lymphadenopathy at the cervical and supraclavicular regions. A left tonsillectomy, wide local excision of the right buttock mass, lymphadenectomy of the right inguinal, iliac regions and obturator basins with femoral vessels sartorius muscle transposition flap coverage was carried out on the patient in accordance to the evidence-based consensus recommendation of our multidisciplinary cutaneous tumor board.
Pre-operative tonsillar biopsy was considered, however, it was not carried out due to the chances of sampling error and bleeding.
The patient was thereafter discharged post-operatively after a 4-day uncomplicated hospital admission in good condition.
Her surgical specimens were evaluated and showed Merkle cell carcinoma measuring 6.5cm at the right buttock with wide cancer-free margins and a mitotic index of 22 mitoses per mm2, metastatic Merkle cell carcinoma of the left tonsil and lymphovascular invasion with 1/16 affected lymph nodes.
The patient has a second-stage rotational flap closure of the gluteal resection defect which was planned a month later. The patient had a stage IV final histopathological staging, for which she started a year course of avelumab 800 mg biweekly as adjuvant therapy.
Decreasing levels of the Merkel cell polyomavirus oncoprotein antibody titer was noticed during the patient’s follow-up visits. It has currently been 11 months since the patient was initially diagnosed with Merkle cell carcinoma, 10 months since she had a pathological diagnosis of tonsillar metastatic Merkle cell carcinoma and she does not show any evidence of disease progression on the basis of contrast-enhanced surveillance CT imaging and physical examination. The patient is closely monitored for evidence of disease progression during her regular follow-ups as she continues her course of avelumab as adjuvant therapy.
Discussion
Neoplasm of the tonsils occur very rarely while malignant metastasis to the tonsils are extremely rare with a prevalence of only 0.8%.
The rare occurrence of metastatic tonsillar tumors is owing to the lack of afferent lymphatic vessels and the abundance of mainly reticuloendothelial cells which are very effective in clearing out tumor cells. In light of this, any malignant metastasis to the tonsils is suggested to be due largely to hematogenous propagation. An alternative route for malignant dissemination of tumor cells in the tonsil is through cervical lymphatics of the tonsils. Malignant metastasis to the palatine tonsil occurs in breast cancer, gastric cancer, colorectal cancer, lung cancer, seminoma and melanomas.
Cancer metastasis to the tonsils is usually present with oropharyngeal symptoms such as pharyngitis, odynophagia, globus and dysphagia reported in 5 previously reported cases.
In this study, however, we presented the first reported patient who had asymptomatic palatine tonsillar metastasis with Merkle cell carcinoma which was seen incidentally. Aggressive multimodal therapy is vital owing to the natural history of the tumor.
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