PRAME Expression in Melanocytic Tumors.

PRAME (PReferentially expressed Antigen in MElanoma) is a melanoma-associated antigen that was isolated by autologous T cells in a melanoma patient. While frequent PRAME mRNA expression is well documented in cutaneous and ocular melanomas, little is known about PRAME protein expression in melanocytic tumors. In this study we examined the immunohistochemical expression of PRAME in 400 melanocytic tumors, including 155 primary and 100 metastatic melanomas, and 145 melanocytic nevi. Diffuse nuclear immunoreactivity for PRAME was found in 87% of metastatic and 83.2% of primary melanomas. Among melanoma subtypes, PRAME was diffusely expressed in 94.4% of acral melanomas, 92.5% of superficial spreading melanomas, 90% of nodular melanomas, 88.6% of lentigo maligna melanomas, and 35% of desmoplastic melanomas. When in situ and nondesmoplastic invasive melanoma components were present, PRAME expression was seen in both. Of the 140 cutaneous melanocytic nevi, 86.4% were completely negative for PRAME. Immunoreactivity for PRAME was seen, albeit usually only in a minor subpopulation of lesional melanocytes, in 13.6% of cutaneous nevi, including dysplastic nevi, common acquired nevi, traumatized/recurrent nevi, and Spitz nevi. Rare isolated junctional melanocytes with immunoreactivity for PRAME were also seen in solar lentigines and benign nonlesional skin. Our results suggest that immunohistochemical analysis for PRAME expression may be useful for diagnostic purposes to support a suspected diagnosis of melanoma. It may also be valuable for margin assessment of a known PRAME-positive melanoma, but its expression in nevi, solar lentigines, and benign nonlesional skin can represent a pitfall and merits further investigations to better assess the potential clinical utility of this marker.

Clinical and pathologic factors associated with subclinical spread of invasive melanoma.

BACKGROUND: Indications to treat invasive melanoma with Mohs micrographic surgery (MMS) or analogous techniques with exhaustive microscopic margin assessment have not been defined. OBJECTIVE: Identify clinical and histologic factors associated with subclinical spread of invasive melanoma. METHODS: This retrospective, cross-sectional study evaluated 216 invasive melanomas treated with MMS and melanoma antigen recognized by T cells 1 immunostaining. Logistic regression models were used to correlate clinicopathologic risk factors with subclinical spread and construct a count prediction model. RESULTS: Risk factors associated with subclinical spread by multivariate analysis included tumor localization on the head and neck (OR 3.28, 95% confidence interval [CI] 1.16-9.32), history of previous treatment (OR 4.18, 95% CI 1.42-12.32), age ≥65 (OR 4.45, 95% CI 1.29-15.39), and ≥1 mitoses/mm2 (OR 2.63, 95% CI 1.01-6.83). Tumor thickness and histologic subtype were not associated with subclinical spread. The probability of subclinical spread increased per number of risk factors, ranging from 9.22% (95% CI 2.57%-15.86%) with 1 factor to 80.32% (95% CI 68.13%-92.51%) with 5 factors. LIMITATIONS: This study was conducted at a single academic institution with a small study population using a retrospective study design that was subject to potential referral bias. CONCLUSION: Clinical and histologic factors identify invasive melanomas that are at increased risk for subclinical spread and might benefit from MMS or analogous techniques prior to reconstruction.

Clinical factors associated with subclinical spread of in situ melanoma.

BACKGROUND: Subclinical spread of in situ melanoma occurs at a wide frequency, ranging from 12% to 71%. OBJECTIVE: To identify clinical factors associated with subclinical spread of in situ melanoma. METHODS: We used a retrospective, cross-sectional study of 674 consecutive in situ melanomas to examine 627 patients treated with Mohs surgery and melanoma antigen recognized by T cells 1 immunostaining. The presence of subclinical spread was correlated with clinical characteristics. Univariate and multivariate logistic regression analyses were performed to generate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Both univariate and multivariate analyses demonstrated significantly increased odds for subclinical spread of in situ melanomas when they were located on the head or neck, at acral sites, or on the pretibial leg (OR 1.97, 95% CI 1.41-3.40); in persons with a history of prior treatment (OR 2.77, 95% CI 1.74-4.420); melanomas of preoperative size >1 cm (OR 1.74, 95% CI 1.23-2.46, P = .002); or in persons ≥60 years old (OR 1.47, 95% CI 1.01-2.13, P = .042). A count prediction model demonstrated that the risk for subclinical spread increased with the number of clinical risk factors. LIMITATION: We used a single-site, retrospective study design. CONCLUSION: Clarifying the risk factors for subclinical spread might help to refine triage of in situ melanomas to the appropriate surgical techniques for margin assessment prior to reconstruction.

Soluble adenylyl cyclase antibody (R21) as a diagnostic adjunct in the evaluation of lentigo maligna margins during slow Mohs surgery.

Margin-controlled staged excision (slow Mohs) has emerged as a preferred method for the treatment of lentigo maligna (LM). The interpretation of margins for LM is one of the most challenging tasks faced by a dermatopathologist. R21 is a mouse monoclonal antibody against soluble adenylyl cyclase (sAC), overexpressed in the nuclei of LM but not in native melanocytes. The objective of this study was to validate the use of sAC immunohistochemistry in histological assessment of slow Mohs surgery margins for LM. Seventeen randomly selected cases of patients who underwent slow Mohs surgery for LM at Lahey Clinic, Burlington, MA, were studied. Ninety-nine margins were stained with R21 and microphthalmia transcription factor antibodies and reevaluated blindly by 2 observers. Sixteen of 17 lesions expressed sAC. In all cases, observers agreed on interpretation of R21 stains. In 85 (86%) margins, there was concordance between routine sections and R21 stains. In 14 margins (14%), the results were discrepant. In 2 margins, R21 identified foci of LM missed on routine sections. In 8 margins, atypical melanocytes, interpreted as positive in routine sections, were negative for R21 questioning the accuracy of the original interpretation. Microphthalmia transcription factor stained nuclei of melanocytes in all margins. We found significant correlation between assessment of margins by sAC immunohistochemistry and routine histology. Evaluation of sAC expression using R21 antibody is a useful diagnostic adjunct in the evaluation of margins of LM during slow Mohs surgery.

Characterization of the cellular infiltrate during successful topical treatment of lentigo maligna with imiquimod.

Lentigo maligna (LM) is an in situ melanoma which usually occurs in sun-damaged skin on the head and neck of elderly patients. Depending on the anatomical site and its size treatment of LM can be problematic and usually includes surgical excision or radiotherapy. Recent reports indicate that topical imiquimod may be an effective treatment. However, no data on the underlying immune response in the skin during treatment of LM with topical imiquimod are available so far. We report a 62-year-old caucasian woman with a histologically verified LM which was successfully treated with topical imiquimod 5% cream. Skin biopsy specimens were obtained before, during (at week 10) and 4 weeks after cessation of topical treatment with imiquimod 5% cream. Histological and immunohistochemical examination was performed in order to detect residual atypical melanocytes and to characterize the inflammatory infiltrate. A complete clinical and histological clearance of the skin lesion was achieved, with no recurrence up to 9 months after the end of treatment. During topical application of imiquimod 5% cream a depletion of epidermal and dermal CD1a+ dendritic cells was observed. The inflammatory infiltrate consisted of CD68+ macrophages and mainly of CD3+ T cells with a slight predominance of CD8+ T cells. An enhanced expression of granzyme B and TIA-1 was also noted particularly in the epidermis and near the dermoepidermal junction. In conclusion, our data indicate that imiquimod 5% cream induces a cytotoxic T-cell-mediated immune response in situ which may account for the complete destruction of the malignant melanocytes in LM. Further clinical trials and longer follow-up periods on the use of imiquimod for LM are warranted.

Immunohistochemical study of melanocytic differentiation antigens in cutaneous malignant melanoma. A comparison of six commercial antibodies and one non-commercial antibody in nodular melanoma, superficially spreading melanoma and lentigo maligna melanoma.

In certain primary and metastatic malignant melanomas diagnostic problems may arise due to their cytologic features and/or absence of synthesis of melanin. As the "classic" combination of S-100 protein and HMB-45 may occasionally fail to stain cells of malignant melanoma, we have tested a series of commercially accessible antibodies which were so far not compared by other authors in the three most frequent subtypes of this tumor. In surgical specimens from 104 cutaneous malignant melanomas (40 nodular melanomas, 46 superficially spreading malignant melanomas and 18 lentigo maligna melanomas) the staining intensity and the proportion of neoplastic cells stained with antibodies to S-100 protein, HMB-45, NKI/C3, NKI/beteb, MART 1 (Melan A), KBA 62 and Mitf was semiquantitatively analysed. The use of this group of antibodies against melanoma-associated antigens revealed it to be a favourable supplement for the bioptical or cytological diagnosis of malignant melanoma in case the traditional/conventional combination of S-100 protein and HMB-45 antibody fails. According to the authors' experience the antibody against KBA 62 has shown to be the most effective antibody followed by the antibodies against MART-1 (Melan A) and NKI/C3.

Treatment of lentigo maligna with topical imiquimod.

A published case report and anecdotal experience suggested that topical imiquimod is an effective treatment for stage 0 melanoma (lentigo maligna). To gauge the efficacy of this therapy, we undertook a trial of topical imiquimod in 30 subjects with histologically confirmed lentigo maligna. Thirty subjects with lentigo maligna were recruited for an open-labelled efficacy trial with daily topical application of imiquimod 5% cream for 3 months. Study subjects were enrolled from the Dermatology service of the University of Oklahoma, the Oklahoma City Veteran's Administration Hospital Dermatology service and from referrals for the study from other practitioners. In order to determine an initial response rate, a four-quadrant biopsy was carried out on all patients 1 month after cessation of treatment, targeting the most clinically and dermatoscopically suspicious areas. Of 28 evaluable subjects who have completed the 3-month treatment phase, 26 (93%) were complete responders and two were treatment failures at the time of the 4-quadrant biopsy. Over 80% of the 28 subjects that completed treatment have been followed for more than 1 year with no relapses. The results of this study demonstrate that topical imiquimod produces a high complete response rate in lentigo maligna when applied daily for 3 months.