Nowadays, surgery procedures and adjuvant therapies are the best choices for the treatment of symptomatic spinal metastases. On the other hand, clinical evidence for spinal metastasis from malignities and skin cancer is generally lacking, probably because they are extremely rare.
Moreover, the incidence of MCC has increased in the last three decades, and currently, optimal management of patients with spinal metastasis from MCC has not yet been clearly established .
MCC is an uncommon neuroendocrine primary skin cancer, named from the neurosecretory granules in the tumor cells that originate from a neural crest derivative of Merkel cells . The first histopathological description was reported by Cyril Toker in 1972; he named the disease such as “trabecular carcinoma of the skin” .
The MCC is more common in Caucasians, males, and individuals greater than 65 years of age .
Similar to other primary skin cancers, this lesion is most commonly located in the sun-exposed areas of the skin such as the head and neck. The common clinical features are cutaneous manifestations such as a violaceous papule, nodule, pedunculated masses, chalazion, or granulation tissue. Moreover, nearly half of the patients have regional lymph node involvement at initial diagnosis and up to 3% of patients present a metastatic disease at the diagnosis .
The most frequent sites of distant metastasis are the lymph nodes, distant skin, lung, and bone .
The central nervous system (CNS) is rarely involved, despite the bone of the cranium and spine could be affected . Furthermore, there are only a few cases of MCC spinal metastasis reported in the literature (Table 1). Most of the reported metastasis are localized in epidural space with concomitant involvement of adjacent bone and/or paravertebral space. In particular, when the adjacent bone and/or neural foramina appear involved, the possibility of epidural extension through these structures should be considered.
Only two authors reported an intradural location of MCC metastasis, and one of these described an intramedullary lesion in an end-stage case of MCC . Abul-Kasim et al. described a patient with a leptomeningeal spread of disease and multiple brain localization that could be explained by the intradural dissemination of MCC metastasis. In our paper, we report the first case of intradural extramedullary metastasis of MCC without other localization in CNS .
The first step of treatment of MCC should be an excision of the primary lesion with a safe margin and prophylactic lymphadenectomy followed by irradiation to the primary site . Merkel cell carcinoma is a highly radiosensitive tumor, and radiotherapy is commonly used as adjuvant therapy after surgery, while chemotherapy is reserved for systemic disease .
In our case, the patient was treated with wide primary surgical excision in 2016, without adjuvant treatment. In January 2021, she underwent surgical bilateral resection of the breast for repetitive lesions from MCC with successive adjuvant chemotherapy. After 10 months, she presented sudden neurological impairment due to a cervical spine intradural lesion with mass effect.
The management of patients with spinal metastasis from malignant skin cancers is controversial and often associated with poor outcomes. Several factors should be considered choosing the best treatment modality. The stage of the disease, patient’s age, overall condition, ambulatory status, and life expectancy are some to be considered.
The exact time of life expectancy is controversial, and some clinicians commonly use a cutoff of 3 months to determine whether surgical intervention should be offered, while others advocate at least 6 months of life expectancy. Decompressive surgery plus radiation is demonstrated to be the preferred treatment for patients with solitary spinal metastases with symptomatic cord compression .
In our case, the patient had a sudden neurological impairment, more than 3 months of life expectancy, and solitary spinal metastasis without other CNS involvement. Laminectomy and complete excision were performed with an improvement of neurological symptoms.
When the spine stability is compromised the stabilization should be considered [4, 8]. Furthermore, when the prognosis is very poor, palliative care (CT, RT) should be the treatment of choice. Only a few articles studied the median survival of patients affected by spinal metastasis from primary skin cancer. Goodwin et al. reported a median survival of 6.3 months despite the type of treatment (surgical and/or medical), whereas the mean survival was 4.6 months, 6.9 months, and 9.1 months from diagnosis of spinal metastasis, respectively, for patients treated with surgery alone, medical treatment alone, and surgery plus adjuvant therapy . A possible bias of this data was that the study comprised a preponderance of case reports and a heterogeneous cohort.
According to the literature, our patient underwent adjuvant radiotherapy treatment, and actually, she is under clinical follow-up. In summary, we reported the first case of solitary intradural extramedullary cervical spine metastasis from MCC. To improve the management of patients with spinal metastasis from skin cancers, we recommend a multidisciplinary discussion to choose the best treatment and consider the metastasis of MCC in the differential diagnosis of spinal metastasis, particularly in patients with skin lesion history. Moreover, further studies are needed to improve the management and outcome of patients with spine metastasis from MCC.