Paraneoplastic and Metastatic Neurologic Complications of Merkel Cell Carcinoma  Scott D.Z. Eggers, MD, Diva R. Salomao, MD, Robert P. Dinapoli, MD, Steven Vernino, MD, PhD  Mayo Clinic Proceedings  Volume 76, Issue 3, Pages 327-330 (March 2001) DOI: 10.4065/76.3.327 Copyright © 2001 Mayo Foundation for Medical Education and Research Terms and Conditions

Figure 1 Two-hertz repetitive stimulation of the femoral nerve using near-nerve needle stimulation. A, Baseline compound muscle action potential (CMAP) amplitude is markedly reduced (0.38 mV), and 2-Hz repetitive stimulation produces a 47% decrement. B, The femoral CMAP amplitude shows 400% facilitation to 1.51 mV after 10 seconds of exercise. Similar but less dramatic findings were seen in the ulnar and peroneal motor studies. These findings are consistent with Lambert-Eaton myasthenic syndrome. Mayo Clinic Proceedings 2001 76, 327-330DOI: (10.4065/76.3.327) Copyright © 2001 Mayo Foundation for Medical Education and Research Terms and Conditions

Figure 2 A, Surgical biopsy specimen. Clusters of tumor cells show a rather uniform appearance. The cells have round vesicular nuclei and scanty ill-defined cytoplasm. Numerous mitotic figures are present (hematoxylin-eosin, original magnification ×200). B, In paraffin sections, immunoperoxidase staining for cytokeratin 20 shows diffuse positivity in the neoplastic cells with a punctate (dotlike) pattern, characteristic of Merkel cell carcinoma (original magnification ×200). C, Cytospin preparation of cerebrospinal fluid shows a cellular specimen represented by a monomorphic population of small round cells, both clusters and single cells, with morphologic features similar to those observed in the surgical specimen. This finding was consistent with metastatic Merkel cell carcinoma (Papanicolaou stain, original magnification ×600). Mayo Clinic Proceedings 2001 76, 327-330DOI: (10.4065/76.3.327) Copyright © 2001 Mayo Foundation for Medical Education and Research Terms and Conditions