Although prominent vascular proliferation is a known feature of various neuroendocrine tumors, it has not been systematically studied in Merkel cell carcinoma (MCC) of the skin. The purpose of this study was to fully characterize the light microscopic, immunohistochemical, and ultrastructural features of vascular changes associated with MCC and to determine their frequency and differential diagnostic implications. Additionally, the presence of human herpesvirus 8 DNA in the lesional tissue was investigated. Of 92 studied cases of MCC, 18 cases (20%) were found to exhibit foci of prominent vascular changes which were classified into the following 6 patterns: pericyte hyperplasia, pyogenic granuloma-like, hemangioendothelioma-like, epithelioid hemangioma-like, peliosis-like, and follicular dendritic cell tumor-like pattern. In addition, Azzopardi phenomenon was observed. These changes occurred singly or in combination. Human herpesvirus 8 DNA was identified by polymerase chain reaction in none of the 18 cases. It is concluded that prominent vascular proliferations may be seen in 20% of MCC, and thereby, MCC resembles neuroendocrine tumors in other organs. When unduly prominent and encountered in a limited biopsy specimen, vascular alterations may represent a potential diagnostic pitfall, but, on the other hand, they themselves may serve as a clue to the correct diagnosis. Human herpesvirus 8 does not play a role in angiogenesis in MCC.

Merkel cell carcinoma of the upper extremity: case report and an update.World J Surg Oncol. 2008 Mar 7;6:32.

BACKGROUND: Merkel cell carcinoma is a rare but aggressive cutaneous primary small cell carcinoma. It is commonly seen in elderly affecting the head, neck, and extremities. Macroscopically may be difficult to distinguish MCC from other small cells neoplasms especially oat cell carcinoma of the lung. CASE PRESENTATION: It is presented a case report concerning a 72 years old male with a MMC on the dorsal aspect of the right wrist. The patient underwent a diagnostic excisional biopsy and after the histological confirmation of the diagnosis a second excision was performed to achieve free margins. No postoperative radiation or adjuvant chemotherapy was given and within 9 years follow up no recurrence was reported. CONCLUSION: Although most cases present as localized disease treatment should be definitive due to high rates of local or systemic recurrence. Treatment includes excision of the lesion, lymphadenectomy, postoperative radiotherapy and chemotherapy depending on the stage of the disease. Even when locoregional control is achieved close surveillance is required due to high rates of relapse.