Histopathologic, genomic, transcriptomic, and functional characteristics of eight melanocytic tumors with BRAF fusions showing stronger MAPK pathway activation compared to BRAF V600E tumors.

BACKGROUND: Activating BRAF gene alterations are central to melanocytic tumor pathogenesis. A small, emerging subset of melanocytic tumors driven by BRAF fusions has distinct therapeutic implications and has been described to have Spitzoid morphology patterns. However, such morphological patterns do not encompass all cases, and little is known about the functional molecular events. MATERIALS AND METHODS: We conducted a retrospective search through our molecular archives to identify melanocytic tumors with BRAF fusions. We reviewed clinical, histopathological, and genomic features. We further explored transcriptomic and protein-level findings. RESULTS: Histopathologic patterns varied, with many cases without a distinctive pattern. We identified novel and diverse BRAF gene fusion partners. Differential transcriptomic analysis between low-risk BRAF fusion tumors and reference BRAF V600E tumors showed no differentially expressed genes. However, quantitatively stronger MAPK pathway activation of BRAF fusion tumors over BRAF V600E tumors was demonstrated by statistically significant stronger staining of p-ERK immunohistochemistry. Gene-specific RNA analysis shows comparable BRAF transcript levels between the two groups. DISCUSSION AND CONCLUSION: The quantitatively stronger activation of the MAPK pathway of BRAF fusion tumors, instead of qualitatively different transcriptomes, may account for the morphology difference from conventional BRAF V600E tumors. BRAF fusions likely act through dysregulated protein function rather than RNA upregulation related to the characteristics of the fusion partners.

Keratoacanthoma centrifugum marginatum.

Keratoacanthoma centrifugum marginatum (KCM) is an uncommon variant of keratoacanthoma. Keratoacanthoma centrifugum marginatums are most commonly seen on sun-exposed surfaces and present with progressive peripheral expansion and raised, hyperkeratotic borders. Central clearing with atrophy and lack of spontaneous clearance are other key clinical characteristics. The majority of cases are benign with a low risk of metastasis. The size of such growths is variable with reported cases ranging from 5.0cm×5.0cm to as large as 20.0cm×14.0cm. Treatment options include surgical excision, oral retinoids, and intralesional chemotherapeutics such as methotrexate or bleomycin. We herein present a case of KCM manifesting as an exophytic, crateriform plaque in a 61-year-old man.

The utility of PRAME immunohistochemistry in the evaluation of challenging melanocytic tumors.

BACKGROUND: PRAME (PReferentially expressed Antigen in Melanoma) immunohistochemistry has demonstrated high specificity for unequivocal melanomas; however, its utility in ambiguous melanocytic neoplasms has yet to be fully elucidated. METHODS: Cases of challenging melanocytic neoplasms were subclassified into one of three categories: challenging, favor benign (FB), challenging, cannot be subclassified (CCS), or challenging, favor malignant (FM). Using a previously published system, whereby cases with diffuse staining (>75%) were considered positive, scoring of PRAME was performed. Additionally, tumors with hotspot staining were also considered positive. RESULTS: Sixteen out of 85 tumors showed positive staining representing 5% of FB tumors, 24% of CCS tumors, and 47% of FM. In FB and CCS tumors, positive staining was mainly encountered in atypical intraepidermal melanocytic proliferations and spitzoid neoplasms. The specificity of positive PRAME staining was 95% and its concordance with the final diagnostic interpretation was 75%. CONCLUSIONS: PRAME positivity is more common in neoplasms favored to be malignant by histopathologic evaluation. Its clinical utility may include early diagnosis of incipient melanoma in situ. Rarely, benign melanocytic neoplasms could show diffuse expression of PRAME, and additional studies are needed to determine optimal utilization. Lastly, hotspot staining may increase its sensitivity without much compromise in specificity.

Rhinoscleroma.

CONTEXT.­: Rhinoscleroma is a rare, chronic, infectious granulomatous process involving the upper respiratory tract caused by gram-negative bacilli, Klebsiella rhinoscleromatis. The site most commonly affected is the nasopharynx; however, lesions in various other locations have been described. OBJECTIVE.­: To review the literature for all the reported cases of rhinoscleroma in the past 5 years. DATA SOURCES.­: Published cases of rhinoscleroma from a PubMed (National Center for Biotechnology Information, Bethesda, Maryland) search were reviewed. CONCLUSIONS.­: Rhinoscleroma in nonendemic regions is extremely rare; however, with increased travel, immigration, and globalization, it is imperative to recognize this entity because the symptoms can be devastating and in some cases fatal. Although nasopharynx is the common site of involvement, unusual sites such as the trachea can be involved in rare cases. Rhinoscleroma can be managed effectively with a combination of antibiotics and surgical debridement and repair; however, recurrence rates do remain high.

Utility of CK7 Versus p16 as a Prognostic Biomarker in CIN 2.

Cervical intraepithelial neoplasia (CIN) 2 is an equivocal diagnosis, with p16 immunohistochemical positivity currently recommended for diagnostic confirmation. Biomarkers characteristic of squamocolumnar junction cells were recently found to be positive in almost all CIN 2 and CIN 3. CIN 1 lesions which express squamocolumnar junction markers (in particular cytokeratin 7 [CK7]) are associated with a higher rate of subsequent high-grade squamous intraepithelial lesion, suggesting that CK7 may be a useful prognostic biomarker for CIN 1. We sought to determine the utility of CK7 as a prognostic biomarker in the setting of morphologic CIN 2, and to compare this to the utility of p16 in this setting. We performed CK7 immunohistochemical on 116 cases originally diagnosed as CIN 2. Of these, 68.1% were p16 and 90.5% were CK7. A total of 19.5% of patients had a subsequent diagnosis of CIN 3 on biopsy or excision; the index CIN 2 lesion was CK7 in all of these cases (sensitivity 100%) and p16 in all but 1 (21/22; sensitivity 95.5%). The specificity of p16 (37.4%) and CK7 (8.0%) for predicting subsequent CIN 3 were significantly different (P<0.001). While p16 expression was significantly associated with subsequent CIN 3 (P=0.002), CK7 expression was not (P=0.202). We conclude that CK7, unlike p16, is not useful as a prognostic biomarker in CIN 2. While it is still promising as a prognostic marker in CIN 1, additional studies are needed to determine optimal staining/interpretation criteria.