Skin involvement in neuroendocrine neoplasia

Neuroendocrine neoplasia (NEN), priory known as neuroendocrine tumours represent the modern approach of traditionally named “carcinoid” tumours. We shortly introduce benign and malign dermatological aspects that are linked to NEN field. This is a multidisciplinary perspective. The paper is a mini-review. 30 articles are included as references. NEN represents 2% of all cancers, being considered orphan disease. Skin and soft tissue are exceptional sites of NEN, the majority are actually secondary spreading of NEN of other locations. Little data have been published related to the topic. Some cases reports showed invasion of dermis and subcutis, probably more frequent in older adults. The entity has been named low-grade neuroendocrine carcinoma of the skin, also named primary cutaneous carcinoid tumour. As seen in NEN diagnosis, the immunohistochemistry is essential like chromogranin A, synaptophysin, neuron specific enolase which are classical neuroendocrine markers and non-neuroendocrine parameters are useful for differential diagnosis like estrogens, androgens and progesterone receptors, GATA3, carcinoembryonic antigen. Merkel cell carcinoma represents the high grade NEN. It has a poor prognosis, with a 30% risk of local metastasis. The risk factors are either viral infection like Merkel cell polyomavirus, either long time exposure to ultraviolet light. The prognostic is similar between the two factors. Surgical removal is the first line therapy and adjuvant treatment is radiotherapy and chemotherapy. Skin NEN represents an exceptional finding of aggressive profile. Their prompt recognition may help the prognosis.