Genomic landscape of circulating tumour DNA in metastatic extramammary Paget's disease.

Although cancer personalized profiling by deep sequencing (CAPP-Seq) of cell-free DNA (cfDNA) has gained attention, the clinical utility of circulating tumour DNA (ctDNA) in extramammary Paget's disease (EMPD) has not been investigated. In this study, genomic alterations in the cfDNA and tumour tissue DNA were investigated in seven patients with metastatic EMPD. CAPP-Seq revealed mutations in 18 genes, 11 of which have not yet been reported in EMPD. The variant allele frequency of some of the mutated genes reflected the disease course in patients with EMPD. In one patient, the mutation was detected even though imaging findings revealed no metastasis. In another patient with triple EMPD (genital area and both axilla), cfDNA sequencing detected the mutation in a rib metastatic lesion, which was also detected in both axilla lesions but not the genital region. Investigations of the ctDNA may be useful towards the elucidation of clonal evolution in EMPD.

Overexpression of Janus kinase 2 protein in extramammary Paget's disease.

Extramammary Paget's disease is a rare malignant tumor of the skin that occurs primarily in the genitocrural region. Although the prognosis of extramammary Paget's disease with distant metastasis is poor, an effective therapy has not been established. Because Janus kinase 2 has attracted attention as a therapeutic target in several cancers, we investigated the expression of the Janus kinase 2 protein and the relationship between its level of expression and clinical significance in 53 patients with extramammary Paget's disease in our hospital. Immunohistochemistry showed that most extramammary Paget's disease tissues were positive for Janus kinase 2 (50/53, 94.3%), and the immunostaining intensity of Janus kinase 2 was correlated with the degree of invasiveness, lymph node metastasis and distant metastasis. Based on these findings, Janus kinase 2 may be a promising therapeutic target in extramammary Paget's disease.

Overexpression of heat shock protein 90 through the downregulation of miR-9-5p in extramammary Paget's disease.

Heat shock protein 90 (HSP90) facilitates diverse cellular processes by interacting process with more than 200 client proteins. Overexpression of HSP90 contributes to the pathogenesis of various malignant tumors, and HSP90 inhibitors attenuate the progression of malignant tumors in vitro/vivo. Numerous clinical trials have used HSP90 inhibitors to treat several cancers, and pimitespib (an HSP90 inhibitor) is covered by insurance for advanced gastrointestinal stromal tumor in Japan. In this study, we investigated the expression pattern of HSP90 and analyzed its clinical significance in extramammary Paget's disease (EMPD). All 77 EMPD tissues investigated were positive for HSP90 expression. The immunoreactivity of HSP90 in fetal cases due to EMPD tended to be highly stained. Although there was no significant difference in HSP90 mRNA levels between 24 paired lesional and nonlesional tissues, microRNA-inhibiting HSP90 levels in tumor tissues were significantly decreased compared with those in normal tissues. Thus, HSP90 may play an important role in the pathogenesis of EMPD and may be a novel therapeutic target for EMPD.

Analysis of microsatellite instability using Promega panel in dermatofibrosarcoma protuberans.

Dermatofibrosarcoma protuberans (DFSP) is a rare neoplasm derived from fibroblasts. Although the frequency of microsatellite instability (MSI) in skin cancer is reported to be less than 5%, there is only one report of the status of MMR in DFSP. The only analytical report of microsatellite stability in which Promega panel is not used, showed that the frequency of MSI-high, MSI-low and microsatellite stable (MSS) cases was 13.9% (5/36), 16.7% (6/36) and 69.4% (25/36), respectively. Thus, the aim of this study was to evaluate the status of MMR in 36 patients with DFSP diagnosed at Kumamoto University. MSI analysis using the Promega panel showed that all cases were MSS, which indicated the absence of MSI in DFSP. This result indicates that the status of MMR may not be useful for the potential therapeutic application of pembrolizumab and the pathogenesis of DFSP may not involve MSI.