Extensive central nervous system involvement in Merkel cell carcinoma: a case report and review of the literature

Abstract

Introduction: Merkel cell carcinoma is a rare malignant cutaneous neoplasm that is locally invasive and frequently metastasizes to lymph nodes, liver, lungs, bone and brain. The incidence of Merkel cell carcinoma has increased in the past three decades.

Case presentation: A 65-year-old Caucasian man presented with a sudden onset of severe headache and a three-month history of balance disturbance. Magnetic resonance imaging revealed a large meningeal metastasis. The radiologic workup showed retroperitoneal and inguinal lymph node metastases. Biopsy of the inguinal lymph nodes showed metastases of Merkel cell carcinoma. Biopsy from three different suspected skin lesions revealed no Merkel cell carcinoma, and the primary site of Merkel cell carcinoma remained unknown. Leptomeningeal metastases, new axillary lymph node metastases, and intraspinal (epidural and intradural) metastases were detected within six, seven and eight months, respectively, from the start of symptoms despite treating the intracranial metastasis with gamma knife and the abdominal metastases with surgical dissection and external radiotherapy. This indicates the aggressive nature of the disease.

Conclusion: To the best of our knowledge, this is the first report in the literature of an intracranial meningeal metastasis of Merkel cell carcinoma treated with gamma knife and of intraspinal intradural metastases of Merkel cell carcinoma. Despite good initial response to radiotherapy, recurrence and occurrence of new metastases are common in Merkel cell carcinoma.

Figure 1

Axial magnetic resonance imaging (MRI) scan at three different occasions. Images (A-C) show the initial MRI with a large right-sided supratentorial meningeal tumor (arrows) with extensive surrounding edema (bright signal, C). D) MRI after treatment with gamma knife shows marked reduction of the tumor size with only little residual tumor (arrow). E-F) MRI six months from the start of symptoms shows leptomeningeal metastases with linear contrast enhancement along the cerebellar sulci (arrows).

Figure 2

Magnetic resonance imaging (MRI) scan of the lumbar spine eight months after the onset of symptoms. T2-weighted (A) and T1-weighted (B-C) images before and after contrast administration show mild contrast enhancing multilobular tumors in the epidural fat behind the dural sac at the level of L3-L4 (black arrows) and a dural sac filled with intradural tumors (white arrows). Note the absence of the normal cerebrospinal fluid signal in the dural sac below the medullary conus. Axial T1-weighted images before (D) and after (E) contrast administration show the epidural metastases lateral and dorsal to the dural sac (black arrows in D; arrowheads in E). The white arrow in E shows the dorsal limit of the dural sac. F) Axial T1-weighted image after contrast administration shows a tumor-filled dural sac (white arrows).