Low Incidence of Oncogenic EGFR, HRAS, and KRAS Mutations in Seborrheic Keratosis

Seborrheic keratosis

Seborrheic keratosis (SK) is the most common benign epidermal tumor in clinical dermatological practice. This review summarizes current knowledge about the clinical and histological appearance, epidemiology, pathogenesis, and treatment of SK. There are different subtypes of SK based on clinical presentation and histologic findings. Several factors, including age, genetic predisposition, and possibly also exposure to ultraviolet radiation, are thought to contribute to the development of SK. The lesions can occur on all areas of the body except for the palms and soles, but the most common sites are the face and upper trunk. The diagnosis is usually made clinically, and in some cases by dermatoscopy or histology. Many patients prefer to have the lesions removed for cosmetic reasons although there is no medical indication. Treatment options include surgical therapy, laser therapy, electrocautery, cryotherapy, and topical drug therapy, which is currently in development. Treatment should be individualized depending on the clinical picture and patient preference.

Clinical and Histopathological Characteristics of Tumors Arising in Seborrheic Keratosis: A Study of 1365 Cases

Objective

The aim of this study was to describe the clinical and histopathological characteristics of seborrheic keratosis (SK) with secondary tumor and identify associated factors.

Methods

This study was a monocentric retrospective case-control study describing the factors associated with the development of tumors in SK. A total of 1365 patients with SK were admitted to our department between 2018 and 2021. All of the histopathological specimens and medical records of these patients were reviewed. We compared the data of 36 patients with tumors arising in SK with those of the remaining 1329 patients with only SK, which were designated the control group.

Results

The incidence of tumors arising in SK that were biopsied was 2.6%. The tumor types included squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and keratoacanthoma (KA). Compared with other patients with SK, elderly patients with immunosuppression, patients presenting surrounding erythema or ulceration, and those with SK in exposed areas had an increased possibility of developing a secondary tumor. Tumors arising within SK have the histopathological features of ulceration, cytologic atypia, mitosis, “malignant horn”, trabecular cell cords, solar elastosis and severe inflammatory infiltration in the dermis.

Conclusion

SK can show malignant progression in a small fraction of SK cases that are biopsied. This study is the first report on the clinical and histopathological characteristics of tumors arising in SK and identifies relevant factors in an Asian population.

Genetic alterations in seborrheic keratoses

Seborrheic keratoses are common benign epidermal lesions that are associated with increased age and sun-exposure. Those lesions despite harboring multiple somatic alterations in contrast to malignant tumors appear to be genetically stable. In order to investigate and characterize the presence of recurrent mutations, we performed exome sequencing on DNA from one seborrheic keratosis lesion and corresponding blood cells from the same patients with follow up investigation of alterations identified by exome sequencing in 24 additional lesions from as many patients. In addition we investigated alterations in all lesions at specific genes loci that included FGFR3, PIK3CA, HRAS, BRAF, CDKN2A and TERT and DHPH3 promoters. The exome sequencing data indicated three mutations per Mb of the targeted sequence. The mutational pattern depicted typical UV signature with majority of alterations being C>T and CC>TT base changes at dipyrimidinic sites. The FGFR3 mutations were the most frequent, detected in 12 of 25 (48%) lesions, followed by the PIK3CA (32%), TERT promoter (24%) and DPH3 promoter mutations (24%). TERT promoter mutations associated with increased age and were present mainly in the lesions excised from head and neck. Three lesions also carried alterations in CDKN2A. FGFR3, TERT and DPH3 expression did not correlate with mutations in the respective genes and promoters; however, increased FGFR3 transcript levels were associated with increased FOXN1 levels, a suggested positive feedback loop that stalls malignant progression. Thus, in this study we report overall mutation rate through exome sequencing and show the most frequent mutations seborrheic keratosis.

BRAF and RAS Mutations in Sporadic and Secondary Pyogenic Granuloma

Pyogenic granuloma (PG) is a common benign vascular skin lesion presenting as a rapidly growing angiomatous papule. The pathogenesis of most sporadic PGs and PGs associated with port wine stains (PWSs) remains elusive. We report that of 10 PGs secondarily arisen on a PWS, 8 showed a BRAF c.1799T>A (p.(Val600Glu)) and 1 a NRAS c.182A>G (p.(Gln61Arg)) mutation. The GNAQ c.548G>A mutation was identified in the PG and in the respective underlying PWS, indicating that PGs originate from cells of the PWS. In contrast to PG, 12 papulonodular lesions, which had developed in the PWSs of seven patients, showed a RAS and BRAF wild-type status. In sporadic PG we identified the BRAF c.1799T>A mutation in 3 of 25, a BRAF c.1391G>A mutation in 1 of 25, and a KRAS c.37G>C mutation in 1 of 25. Mutation-specific immunohistochemical detection of BRAF p.(Val600Glu) confirmed endothelial cells as carriers of the mutation in secondary and sporadic PG. Our study identifies the BRAF c.1799T>A mutation as a major driver mutation in the pathogenesis of, particularly, secondary PG. These data shed light on the hitherto undetermined genetic basis of PG and classify PG as a benign neoplasm.

Presence of human polyomavirus 6 in mutation-specific BRAF inhibitor-induced epithelial proliferations

IMPORTANCE

A frequent adverse effect of mutation-specific BRAF inhibitor therapy is the induction of epithelial proliferations including cutaneous squamous cell carcinomas. To date, the only factor identified contributing to their development is the activation of the mitogen-activated signal transduction cascade by mutations in the RAS genes. However, these mutations explain only 60% of the tumors; hence, it is important to identify what is causing the remaining tumors.

OBJECTIVE

To test for the presence of human papillomaviruses (HPVs) and the recently identified human polyomaviruses (HPyVs), Merkel cell polyomavirus (MCPyV), and trichodysplasia spinulosa-associated polyomavirus (TSPyV), as well as HPyV-6, HPyV-7, HPyV-9, and HPyV-10, in epithelial proliferations occurring after BRAF inhibitor therapy to determine whether these oncogenic viruses may contribute to BRAF inhibitor-induced skin tumors.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective study at a university hospital in Austria of epithelial proliferations that developed in patients with melanoma after initiation of treatment with the BRAF inhibitor vemurafenib. Samples were analyzed for (1) presence of the most frequently observed RAS mutations by SNaPshot technology, (2) detection of the viruses by real-time polymerase chain reaction, and (3) presence of capsid proteins of the most abundantly detected virus by immunohistochemical analysis.

MAIN OUTCOMES AND MEASURES

RAS mutational status, as well as HPV and HPyV presence, in BRAF inhibitor-induced epithelial proliferations.

RESULTS

Eighteen biopsy samples from 6 patients were retrieved from our hospital's archive. We identified RAS mutations in 10 (62%) of the 16 samples with clear results. DNA of HPyV-9, HPyV-10, and TSPyV were virtually absent in the samples. MCPyV DNA was present in 13 of 18 samples, and HPV, HPyV-6, and HPyV-7 DNA were present in all samples. In general, the amount of DNA encoding the latter viruses was rather low, with the exception of HPyV-6 in several samples of 1 individual patient. Notably, the relevance of the presence of HPyV-6 in the epithelial proliferation was underlined by immunohistochemical detection of the core protein VP1 of HPyV-6.

CONCLUSIONS AND RELEVANCE

The presence of both high HPyV-6 DNA load and VP1 protein suggests that polyomaviruses may contribute to the epithelial proliferations observed in patients receiving BRAF inhibitor therapy, albeit the relative impact as compared with that of RAS mutations appears circumstantial.