Pathologists will inevitably encounter melanocytic neoplasms, which are difficult to classify as melanocytic nevus or melanoma by histopathologic examination alone. While diagnostic confidence and uncertainty depend on one's level of experience and expertise, even the most experienced melanocytic lesion expert…
There is currently no consensus definition on what constitutes a “spitzoid” melanoma. The term is most often used in a practical sense referring to a diagnostic pitfall: a melanocytic neoplasm that at first glance simulates the appearance of a Spitz…
The term nevoid melanoma refers to melanomas, which closely resemble a melanocytic nevus under the microscope. It primarily refers to a diagnostic pitfall. In principle any type of nevus could be mistaken for melanoma, and the term “nevoid” melanomas could…
Any melanoma, including the common variants superficial spreading, lentigo maligna, and acral lentiginous melanoma, may form an invasive tumor nodule. However, the presence of a prominent nodule does not equate a nodular melanoma (NM) subtype ( Fig. 15.1 ). According…
The term superficial spreading melanoma (SSM) is commonly used to refer to melanomas characterized by a combination of clinical and histopathologic findings. They usually occur at intermittently sun-exposed sites, manifest as peripherally spreading surface lesions, and display an intraepidermal growth…
Features of traumatized or persistent nevi appearing at the site of prior surgery may mimic melanoma, a phenomenon recognized for several decades. The histologic distinction between a persistent nevus and a regressing melanoma may in some cases, especially in partial…
Special site nevi or nevi with site-related atypia are terms used to describe melanocytic nevi located in some anatomic regions that, although benign, show unusual or atypical microscopic findings that may lead to diagnostic confusion with melanoma. A number of…
The diagnosis of Spitz nevi and their distinction from melanoma is one of the most difficult tasks in neoplastic dermatopathology. Before a group of melanocytic proliferations was accepted as benign and named Spitz's nevus, similar lesions in children had been…
The term congenital melanocytic nevus (CMN) refers to a melanocytic nevus that either was present at birth or became apparent by the end of the first year of life. The term tardive CMN is used for a melanocytic nevus not…
Acquired melanocytic nevi are thought to result from activation of oncogenes either through an activating mutation or translocation, allowing for clonal proliferation of the affected melanocytes. In the majority of common acquired, including the so-called dysplastic, nevi, the initiating oncogenic…