Immunophenotype and possible origin of nevi with phenotypical heterogeneity

Spindle cell melanocytic lesions--part I: an approach to compound naevoidal pattern lesions with spindle cell morphology and Spitzoid pattern lesions

Melanocytic lesions show great morphological diversity in their architecture and the cytomorphological appearance of their composite cells. Whereas functional melanocytes reveal a dendritic cytomorphology and territorial isolation, lesional naevomelanocytes and melanoma cells typically show epithelioid, spindled or mixed cytomorphologies and a range of architectural arrangements. Spindling is common to melanocytic lesions, and may be either a characteristic feature or a divergent appearance. The presence of spindle cells may mask the melanocytic nature of a lesion, and is often disconcerting, either because of its infrequent appearance in a particular lesion or its interpretation as a dedifferentiated phenotype. Spindle cell melanocytic lesions follow the full spectrum of potential biological outcomes, and difficulty may be experienced judging the nature of a lesion because of a lack of consistently reliable features to predict biological behaviour. Over time, recognition of numerous histomorphological features that may portend a more aggressive lesion have been identified. However, the translation of these features into a diagnostic entity requires a gestalt approach. Although most spindle cell melanocytic lesions can reliably be resolved with this standard approach, problem areas do exist and cause no end of grief to the surgical pathologist or dermatopathologist. In this review, the authors present their algorithmic approach to spindle cell melanocytic lesions and discuss each entity in turn, in order to (1) model a systematic approach to such lesions, and (2) provide familiarity with those melanocytic lesions that either typically or occasionally display a spindled cytomorphology.

Spontaneous involution of congenital melanocytic nevi of the scalp

Large or giant congenital melanocytic nevi are rare. They are associated with a risk of melanoma, which is poorly quantified, and often represent a major cosmetic problem. Surgical intervention is the most common treatment, although dermabrasion or curettage in the first weeks of life is used in some centers. When these nevi occur in the scalp, the risk of melanoma has been reported to be lower. Here we describe a series of children in whom large congenital melanocytic nevi on the scalp appeared to spontaneously involute. Therefore, our findings indicate that these nevi also have a better prognosis cosmetically. It is suggested that the decision about surgical treatment should be deferred until the maximal improvement in appearance has occurred during the first 2 years of life.