Merkel cell carcinoma (MCC) is an aggressive tumor with an uncertain histogenesis typically arising on sun-damaged skin of the elderly. It has rarely been described in association with other tumors such as epithelial, melanocytic, and mesenchymal, but not vascular neoplasias. However, an exuberant vascular reaction is considered a common phenomenon in neuroendocrine neoplasms, where it can even obscure the proliferating cells and mimic a primary vascular neoplasia. A 47-year-old man was referred for the evaluation of a long-lasting reddish skin tumor located on the right buttock. After 2 punch biopsies, the patient underwent surgical excision of the lesion. Histological examination showed a dermal florid, benign vascular proliferation overlying some large deep coalescent nodules made up of monomorphous round cells with scant cytoplasm and a high mitotic activity. After the appropriate immunohistochemical stainings, a final diagnosis of hemangioma overlying a previously unrecognized MCC was rendered. Whether the angiomatous proliferation should be considered an exuberant reaction to the tumor, induced by an angiogenetic drive, or a true hemangioma is somewhat controversial. The main point is that such a neoplastiform angiomatous proliferation may represent a potential diagnostic pitfall, especially in limited specimens, and that an accurate clinicopathologic correlation is always needed. In our case, even if additional punch biopsies had been performed, the vascular proliferation would dominate the histological picture and an accurate diagnostic conclusion would probably not be reached due to the deep location of the MCC.
ASJC Scopus subject areas
- Pathology and Forensic Medicine