PMC7533778_01
(a, axial view) CT scan with contrast demonstrated a hyperdense rounded mass in the subcutaneous tissue of the left side of the neck, posterior to the trapezius muscle, corresponding to the patient's palpable primary mass (red arrow). (b, coronal view) Several lymph nodes (red arrow) in the posterior triangle anterior to the trapezius muscle ranging in size up to 1.5 cm in diameter were demonstrated on CT scan.
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Several lymph nodes in the posterior triangle anterior to the trapezius muscle ranging in size up to 1.5 cm in diameter were also appreciated on CT scans (Figure 1).
(a) Magnification 400x, hematoxylin and eosin stain of the left neck; Merkel cell carcinoma primary tumor demonstrates numerous mitoses and neuroendocrine nuclei. (b) Magnification 200x, MCC left neck primary highlighting lymphovascular invasion. (c) Magnification 400x, immunohistochemistry demonstrates perinuclear dot-like immunostaining positive for cytokeratin 20. (d) Magnification 40x, MCC primary tumor of the left neck in subcutaneous tissue.
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The tissue was positive for synaptophysin, chromogranin, and cytokeratin 20 in a perinuclear dot-like distribution (Figure 2) as well as CAM5.2 and p16.
Timeline of patient's clinical course highlighting surgical excision, radiation, and MCPyV antibody panel AMERK results for the treatment and management of his MCC, as well as rituximab infusions for his paraneoplastic autoimmune encephalitis. Day 0 is set to his initial MCC diagnosis. Red: diagnoses; blue: AMERK titers; green: treatment interventions for MCC and encephalitis, including wide local excision, IMRT, and rituximab infusions (1 g); black: seizures; purple: latest follow-up scans and EEG.
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During this time, he completed two doses of rituximab for his anti-NMDAR encephalitis (Figure 3). His AMERK tests continued to trend downward to 210 STU but remained positive for oncoprotein antibody in serum (AMERK of <74 STU is considered negative) (Figure 3).