Clinical emergence of neurometastatic merkel cell carcinoma: a surgical case series and literature review

Abstract

Merkel cell carcinoma (MCC) is a rare cutaneous neuroendocrine neoplasm of possible viral origin and is known for its aggressive behavior. The incidence of MCC has increased in the last 15 years. Merkel cell carcinoma has the potential to metastasize, but rarely involves the central nervous system. Herein, we report three consecutive surgical cases of MCC presenting at a single institution within 1 year. We used intracavitary BCNU wafers (Gliadel(®)) in two cases. Pathological features, including CK20 positivity, consistent with MCC, were present in all cases. We found 33 published cases of MCC with CNS involvement. We suggest that the incidence of neurometastatic MCC may be increasing, parallel to the increasing incidence of primary MCC. We propose a role for intracavitary BCNU wafers in the treatment of intra-axial neurometastatic MCC.

Fig. 1

T1-weighted gadolinium-enhanced pre-operative MRI of the brain from Case 1 in axial a and coronal b sections demonstrating an irregularly enhancing and partially cystic lesion in the right parietal lobe, with minimal surrounding edema. T1-weighted gadolinium-enhanced pre-operative MRI of the brain from Case 2 in axial c and coronal d sections demonstrating an irregularly enhancing lesion in the right posterior temporal lobe, with minimal surrounding edema and shift of the midline structures to the left

Fig. 2

T1-weighted gadolinium-enhanced pre-operative MRI of the brain from Case 3 in axial a and coronal b sections demonstrating a subgaleal mass with involvement of the underlying bone and dura. Pre-operative axial head CT with bone windows c scan demonstrates subtle bony change with slightly irregular hyperostotic calvarium, but no gross osteolysis. Postoperative axial head CT shows the region of calvarial reconstruction with titanium mesh and methylmethacrylate d

Fig. 3

Case 2 a Light micrograph of the metastatic MCC specimen stained with hematoxylin and eosin at ×60 magnification shows a highly cellular specimen comprised of small to medium sized round cells with high nuclear to cytoplasmic ratio. The oval nuclei have a fine granular chromatin pattern. Mitotic figures were evident. b Light micrograph of the metastatic MCC specimen stained with CK-20 at ×60 magnification displays the paranuclear dot staining pattern typical of MCC

Fig. 4

The graph depicts the cumulative number of case reports and case series describing neurometastatic MCC vs. the year of publication