Nevi Of Special Sites Research Articles

Recognizing Histopathological Simulators of Melanoma to Avoid Misdiagnosis.

Melanocytic lesions have a wide morphological spectrum, ranging from benign nevi to malignant melanoma. In contrast to a diagnosis of a benign nevus, a diagnosis of melanoma could mean intensive treatment, lifetime monitoring, and a worse prognosis. Therefore, melanocytic tumors are notoriously challenging and associated with a high risk of litigation in surgical pathology. After describing the basic features of nevi and melanoma, this article describes the detailed clinical and histological features of those lesions that share many similar features with melanoma. The entities included are Spitz nevi and atypical Spitz tumors (AST), Reed nevus, dysplastic nevus, cellular blue nevus (CBN), deep penetrating nevus, combined nevus, recurrent nevus, irritated nevus, congenital pattern nevus, acral nevus, and nevi of special sites. Knowledge of these imitators can help pathologists distinguish between benign and malignant cases and avoid misdiagnosis.

DERMOSCOPY OF THE MONTH Nevi with Site-Related Atypia

AbstractThe term “nevi of special sites” refers to melanocytic nevi of specific anatomic locations including the breast, axillae, umbilicus, genitalia, flexural areas, acral surfaces, ear, scalp and the conjunctiva. Nevi from these anatomic sites display sometimes dermoscopic and histological features of melanoma, resulting in unnecessarily high rates of excisions and re-excisions. Some authors have categorized nevi excised in the axillary, breast, umbilical and perineal areas as the nevi of the milk line. Two patients, a 32-year-old female and 23-year-old male with breast and periumbilical pigmented lesions, presented to our Department during 2017. Dermoscopy revealed features that were highly specific for melanoma. Excisional biopsies were done and histopathology revealed benign nevi with present site-related atypia. Irregular blotches, non-uniform radial streaks, blue-gray veil, and regression are the most specific features of melanoma of the breast and flexural areas. Excision is always recommended in pigmented lesions on the breast and flexural areas, which exhibit these features. However, larger studies are needed to define specific criteria required to distinguish special-site nevi from melanoma.

Dermoscopic and confocal features of an axillary "special site" nevus.

“Nevi of special sites” is a term that denotes melanocytic nevi presenting in specific anatomic locations including the scalp, genital area, flexural sites, and acral sites [1]. Nevi from these anatomic sites display at times histopathologic features that may lead the reading pathologist to recommend re-excision of these benign nevi. Reflectance confocal microscopy (RCM) is a noninvasive imaging tool that allows for visualization of epidermal, dermal-epidermal junctional (DEJ), and superficial dermal tissue structures at cellular level resolution. RCM features of special site nevi have not been previously described in the literature. Defining the RCM characteristics of special site nevi may increase diagnostic accuracy and assist in ruling out melanoma.Here, we report a case of a pigmented lesion appearing in the axilla of a patient with a recently diagnosed melanoma. Dermoscopic and histopathologic results were consistent with the diagnosis of nevus in flexural anatomic sites. In this case, RCM showed a regular honeycomb pattern of epidermal keratinocytes and enlarged, non-homogenous, discohesive nests at the DEJ, a pattern that corresponded well with the histopathologic findings. Larger studies are needed to establish RCM features of special site nevi in order to reliably rule out melanoma and lower the rate of unnecessary excisions of these benign nevi.

To the Editor

The case report by Hoffman, Hartschuh, and Flux, titled, “Combined Nevus with Dermally Located Pagetoid Cells in the Perianal Region: A New Variant of Site-Related Histological Atypia” in the August issue of this journal was of considerable interest. Their case study is a welcome addition to our limited body of knowledge concerning nevi of special sites and combined nevi. However, we disagree with their use of the term “pagetoid” to refer to dermally located melanocytes. If we understand correctly, readers now are asked to accept that pagetoid melanocytes can be recognized not by their location in the epidermis, the currently accepted definition, but instead by nonspecific and minimal morphologic features: “…abundant pale cytoplasm with dusty melanin.” Pagetoid melanocytes are recognized by their presence and “scatter” within the epidermis. Pagetoid melanocytes are, by definition, intraepidermal. Their cytomorphologic features vary considerably from case to case. To claim that they can be recognized simply by “abundant pale cytoplasm with dusty melanin” is, to say the least, a challenging concept. Many melanomas that involve the dermis may have melanocytes with these features. Are we to believe that they are pagetoid cells? To do so would make the term pagetoid no longer meaningful.

Atypical Genital Nevi

Atypical genital nevi are rare melanocytic lesions that most commonly arise on the vulva of young women. They are currently regarded as nevi of special sites, in that despite histologically worrisome features, their clinical behavior is reportedly benign. However, only few studies with limited follow-up data are available. To better characterize the clinical presentation and behavior of these lesions and to further delineate their histologic features, we retrieved 56 atypical genital nevi arising in the lower female genital tract from our departmental and consultation files. The 56 lesions arose in 55 female patients with a median age of 26 years (range, 6 to 54 y). The dominant histologic feature was a lentiginous and nested junctional component composed of prominent round or fusiform nests, which often showed retraction artifact and/or cellular dyscohesion. Cytologic atypia was mild in 11 cases (20%), moderate in 34 (60%), and severe in 11 (20%). Ten cases (18%) showed focal pagetoid spread, with extension to the granular layer and stratum corneum in 1 case. The atypical junctional melanocytic proliferation was associated with a large common dermal nevus component that dominated the lesion in 26 cases (46%). Adnexal spread (46%) and nuclear atypia of melanocytes situated in the superficial dermis (39%) were relatively common, but dermal mitoses (7%) were uncommon and maturation was present in all cases. A broad zone of dense eosinophilic fibrosis within the superficial dermis was a frequent finding (41%). Clinical follow-up was available in 45 cases (80%) with a median follow-up period of 3.5 years (range, 1 to 16 y). Only 1 lesion recurred, 1.5 years after the initial excision. The original nevus in this patient had only mild cytologic atypia and was present at the margins of excision. The recurrent/persistent nevus was reexcised, and there was no further clinical recurrence in 11.5 additional years of follow-up. Our data support the hypothesis that atypical genital nevi have a benign clinical course despite their occasionally striking cytologic and architectural atypia. Awareness and recognition of this group of melanocytic lesions is important to avoid over diagnosis as melanoma with subsequent wide excision and possibly sentinel lymph node biopsy.

Special Site Nevi in Pregnancy

Abstract:Nevi of special sites occur on genital, breast, flexural, and acral skin. Lesions at these locations have distinctive histologic features and display both architectural and cytologic atypia. They can simulate dysplastic nevi or melanoma and therefore cause diagnostic concern. Rarely, pregna

Precursors to melanoma and their mimics: nevi of special sites

Melanocytic nevi, which are benign tumors of melanocytes, may have occasional cosmetic significance but, for the most part, they are important only in relation to melanoma. Nevi are the most important simulants of melanoma, both clinically and histologically, and can usually be reliably distinguished from melanomas using published criteria. Some lesions are characterized by greater degrees of atypia and may be more difficult to diagnose. Dysplastic nevi are among the most important simulants of melanoma. Nevi may also be important as potential precursors of melanoma; however, most nevi are stable and will not progress to malignancy. Nevi are vastly more common than melanomas and the rate of progression of individual lesions is very low. Therefore, nevi are not as a rule managed by wholesale excision to prevent melanoma. Nevi are also important as risk markers, identifying individuals at greater risk of developing melanoma in the future. Dysplastic nevi and, to a lesser extent, common acquired and congenital nevi are among the most important melanoma risk markers. Nevi of special sites have been identified as nevi that may show atypical features suggestive of a dysplastic nevus or of a melanoma. However, they are not risk markers and they are not malignancies. Nevi of genital skin, acral skin, and flexural skin are among the most important ‘nevi of special sites'. It is important, in considering the differential diagnosis of a lesion in a special site, to avoid overcalling such a lesion as a melanoma or a dysplastic nevus because this could lead to excessive treatment. Conversely, it is important to avoid undercalling a lesion that is a dysplastic nevus or a melanoma as a nevus of special sites, because in this circumstance a patient could lose the opportunity either for surveillance to recognize a developing melanoma at an early, curable stage, or for definitive treatment of an established malignancy. In this monograph, dysplastic nevi and nevi of special sites are compared and contrasted in relation to melanoma.