Use of PRAME immunostaining to distinguish early melanoma in situ from benign pigmented conditions.

BACKGROUND: PRAME (PReferentially expressed Antigen in MElanoma) is an antigen that shows marked overexpression in melanoma compared to normal skin melanocytes. PRAME immunohistochemistry has proven effective in distinguishing melanocytic nevi from melanoma, but it is unclear if it may be used to distinguish melanoma in situ from other benign pigmented lesions. In particular, differentiating from melanocytic hyperplasia in sun-damaged skin is sometimes clinically and histopathologically challenging. We hypothesized that PRAME staining of solar lentigo, sun-damaged skin, and melanoma in situ would aid in setting a threshold of positivity that could be useful in evaluating such conditions. METHODS: We collected and stained typical examples of solar lentigo, melanoma in situ, and non-lesional sun-damaged skin by PRAME immunohistochemistry to assess a potential cutoff of PRAME positivity. RESULTS: Solar lentigo and non-lesional sun-damaged skin had 10 or fewer PRAME-positive cells per millimeter (mean 1.2), on the other hand melanoma in situ had at least 16 (mean 75.1). CONCLUSIONS: PRAME immunostaining appears sensitive and specific in the current series. This could be clinically useful for distinguishing melanoma in situ from benign melanocytic hyperplasia in sun-damaged skin. However, further studies are required to determine if 10 cells per millimeter is an acceptable threshold of positivity.

Differentiation of Basal Cell Carcinoma Subtypes in Multi-Beam Swept Source Optical Coherence Tomography (MSS-OCT).

BACKGROUND: Optical coherence tomography (OCT) is a technique that enables real-time in-vivo examination of tissue. This technology provides the clinician with the potential to use a non-invasive tool in the identification and diagnosis of many skin lesions. However, the diagnostic features of basal cell carcinoma have not yet been described with comparison to their histopathology.
OBJECTIVES: To identify and describe key features of basal cell carcinoma (BCC) and its subtypes as they present in multi-beam Swept Source - OCT (MSS-OCT), and to correlate those against conventional histopathology.
METHODS: A total of 40 lesions were assessed by MSS-OCT prior to biopsy. 60-slice OCT images of the lesions were obtained and correlated with histology sections taken in the same plane. OCT scans were assessed retrospectively by a panel to determine the OCT criteria for BCC and its subtypes.
RESULTS: The following diagnostic criteria were identified: hyporeflective ovoid structures (40/40), dark halo boundaries (38/40), epidermal thinning (28/40), and collagen compression (14/40). Lesional tissue also showed a destruction of layers when compared to the surrounding normal tissue. In addition to the shared criteria, other subtypes showed distinct diagnostic criteria.
CONCLUSION: With its higher sensitivity, using MSS-OCT allowed for non-invasive, accurate identification of the key diagnostic features of BCC and its subtypes with high correlation to the histopathologic features found with biopsy.

J Drugs Dermatol. 2016;15(5):545-550.

PRAME immunohistochemistry compared to traditional FISH testing in spitzoid neoplasms and other difficult to diagnose melanocytic neoplasms.

PRAME (PReferentially expressed Antigen in Melanoma) is a gene first identified in melanoma. It has been proposed as a useful marker to differentiate melanoma from benign melanocytic neoplasms. Recently genomic testing using fluorescence in situ hybridization has been used to aid in the diagnosis of difficult melanocytic neoplasms. We have compared PRAME staining to FISH testing results in 83 difficult to classify melanocytic neoplasms which showed spitzoid histologic features. A relatively low sensitivity of 29.6% and high specificity of 76.8% is seen with PRAME staining as compared to genomic testing with fluorescence in situ hybridization. This study highlights the limitations of PRAME staining in spitzoid neoplasms.

Differentiating Early Stage Cystic Keratoacanthoma, Nodular Basal Cell Carcinoma, and Excoriated Acne Vulgaris by Clinical Exam, Dermoscopy, and Optical Coherence Tomography: A Report of 3 Cases.

Making accurate diagnoses when certain lesions are in a relatively young stage can prove challenging, as their "textbook descriptions" are often not fully apparent, and may in fact be markedly different. The authors present three interesting cases of early lesions that were clinically difficult to differentiate from one another: a cystic variation of a keratoacanthoma squamous cell carcinoma, a basal cell carcinoma, and an excoriated facial acne vulgaris. The subtle clinical nuances found in each of these cases demonstrated the importance of a careful clinical evaluation; however, this was not sufficient for adequate assessment of whether or not to biopsy. With early lesions such as these, the use of the noninvasive imaging modalities of dermoscopy and optical coherence tomography becomes critical in order to avoid unnecessary biopsy. The discussion of the clinically and dermoscopically challenging features is both instructive and enlightening. Oftentimes, "textbook descriptions" of lesions focus on the description of an already mature stage of growth, despite the fact that we continue to strive toward earlier detection of potential malignancies. With this in mind, the features found with optical coherence tomography proved essential to the elucidation of these difficult lesions. These three interesting cases illustrated the challenges encountered when dealing with early lesions specifically. The authors bring to light features in each of these cases that are often not thought of as being the "typical" presentation in each lesion category and demonstrate the clinical utility of noninvasive devices in difficult-to-diagnose cases such as these.