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Atypical Spitz nevus (tumor)
Published in Longo Caterina, Diagnosing the Less Common Skin Tumors, 2019
In 1989, Smith and colleagues2 described the “Spitz nevus with atypia and metastasis.” A few years later, Barnhill et al.3,4 defined the category of metastasizing Spitz tumor, or atypical Spitz tumor. Recently, these lesions have been included in the group of melanocytic tumors of uncertain malignant potential.11,12 Currently there are three interpretations regarding the taxonomy of ASTs: they are nevi that have features in common with melanoma but are biologically benign,they are intermediates between nevi and melanomas,they represent a subset of melanomas with a better prognosis than conventional melanomas.13
The Markers Auxiliary in Differential Diagnosis of Early Melanomas and Benign Nevi Sharing Some Similar Features Potentially Leading to Misdiagnosis – A Review of Immunohistochemical Studies
Published in Cancer Investigation, 2022
Łukasz Kuźbicki, Anna A. Brożyna
Although nevi generally exhibit attributes representative for benign lesions, some of their types can have some hallmarks of melanoma. Spitz nevi, although usually symmetric with sharp lateral demarcation and cell maturation in depth, are characterized by the presence of large epithelioid and/or spindle shaped melanocytes. At the border of the epidermis and dermis, elongated nests of spindle cells in a vertical orientation to the skin surface adjacent to elongated rete ridges are often observed (4). A special form of spindle cell lesion is Reed nevus with pigmented melanocytes in nests and melanophages at the base (12). In nevi of spindle and/or epithelioid cells, the nests can be quite large and bridge the entire thickness of the epidermis. Disordered junctional nesting manifests by variation in size, shape, orientation, cellular cohesion and horizontal bridging of the nests. However, single cells are sometimes observed also in the upper layers of the epidermis mimicking pagetoid spread. Such features can make these benign lesions difficult to be distinguished from in situ or early invasive melanoma, especially of superficial spreading type (4,10,11). Ackerman (11) very emphatically stated that he did not know a pathologist with a long experience who would not confuse Spitz nevus for melanoma at least once. Similarly problematic dysplastic nevi are often asymmetric with lentiginous proliferation and junctional nests characterized by a variety of size, shape, and bridging. Moreover, a lack of cellular cohesion is observed in junctional nests. The key features of these nevi constitute disordered intraepidermal proliferation and atypia of melanocytes. However, the dysplasia attributes can vary in terms of severity (4). In some cases, dysplastic nevi can be confused with lentigo maligna or early stages of SSM (4,10). In the WHO classification published in 2018, melanocytic tumors of uncertain malignant potential were described. These lesions are characterized by the proliferation of atypical melanocytes in the skin, suggesting their tumorigenic potential. Superficial atypical melanocytic proliferation of unknown significance was defined as the proliferation of atypical pigment cells localized within the epidermis and superficial zones of the dermis up to 0.8 mm thickness with difficult to determine symmetry and ambiguous cell maturation without ulceration and mitotic activity (8,13). However, the histopathologic evaluation of the lesion as benign or malignant is of key importance for the further treatment of the patient.