Expression of p15 in a spectrum of spitzoid melanocytic neoplasms

Ancillary immunohistochemistry testing for loss of p16 in melanoma: A systematic review and meta-analysis of diagnostic accuracy studies

BACKGROUND

Ancillary immunohistochemistry testing for p16 loss has been proposed as a diagnostic tool for melanoma, but its accuracy remains uncertain.

METHODS

A systematic review and meta-analysis were conducted on 26 studies involving 979 melanomas and 974 nevi.

RESULTS

Through bivariate analysis of data across all cut-off values, the sensitivity and specificity were calculated to be 0.55 (95% confidence interval [CI]: 0.38, 0.70) and 0.85 (95% CI: 0.70, 0.94), respectively. Summary estimates of diagnostic accuracy fell below recommended thresholds for effective tests, but subgroup analysis suggested that p16 loss could aid in diagnosing ambiguous lesions as melanoma in certain scenarios. However, the presence of p16 expression in these contexts does not definitively rule out melanoma. The findings were limited by underpowered exploratory study designs at risk for bias in patient selection and test interpretation.

CONCLUSIONS

While the use of p16 immunohistochemistry for detecting melanoma is not universally reliable, it may serve as a confirmatory test in differential diagnoses involving common, congenital, acral, Spitz, and deep penetrating nevi. Nevertheless, further studies are needed to validate its utility. Until then, the application of p16 immunohistochemistry in melanoma diagnosis should be regarded as experimental.

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

Although most melanocytic skin lesions are correctly diagnosed, numerous studies have shown interobserver disagreement. This review analyzes 20 molecules as immunohistochemical markers for distinguishing dysplastic and/or Spitz nevi from early melanomas (in situ, Clark level I or II and/or Breslow thickness at most 1 mm). The detected presence and/or level of tested molecules was significantly different in early melanomas than in dysplastic and Spitz nevi for six and seven potential markers, respectively. The most promising results were obtained for 5-hydroxymethylcytosine, cyclooxygenase-2 and PReferentially expressed Antigen in MElanoma whose levels were different in dysplastic and Spitz nevi compared to early melanomas.

Spitz Nevus: Review and Update

The Spitz nevus is an uncommon melanocytic nevus. These lesions classically appear in childhood as a red, dome-shaped papule. They appear rarely in adults and may be pigmented. The Spitz nevus can develop suddenly and grow rapidly, reaching a 1-cm diameter in 6 months or less. There are 3 classes of spitzoid neoplasms: typical Spitz nevus, atypical Spitz nevus, and spitzoid melanoma. The diagnosis should be cautiously differentiated, especially in children. Immunohistochemistry and molecular studies have been helpful in differentiating difficult cases; however, no set of criteria has been accepted to predict biological behavior of atypical Spitz nevi.