The absence of BRAF, FGFR3, and PIK3CA mutations differentiates lentigo simplex from melanocytic nevus and solar lentigo

Seborrheic Keratosis With Malignant Transformation (Invasive or Noninvasive Squamous Cell Carcinoma Arising in Seborrheic Keratosis): A Clinicopathologic and Immunohistochemical Study of 11 Cases

ABSTRACT

Seborrheic keratosis is a common benign neoplasm composed of basaloid keratinocytes. However, little is known about the malignant transformation of the tumor. Eleven cases of seborrheic keratosis with malignant transformation were analyzed. The 11 patients included 5 male patients and 6 female patients with a median age of 75 years at diagnosis (68-90 years). The tumors arose at various sites from the scalp (n = 3) to the lower leg (n = 2). The median tumor size was 12 (10-32) and 40 (20-75) mm in 7 noninvasive and 4 invasive cases, respectively. One patient exhibited in-transit skin metastasis. Histopathology of the malignant components resembled porocarcinoma or inverted follicular keratosis. Bowenoid and pagetoid spreading was frequently observed. The malignant components expressed cytokeratin 5/6 (100%) and GATA3 (73%), but not cytokeratin 7 (0%), cytokeratin 19 (9%), BerEP4 (0%), c-kit (0%), and NUT (0%). No significant immunoreactivity of YAP1 was observed in any of the cases. Mutant-type immunostaining of p53 and PTEN was observed in 91% and 82% of the cases, respectively. An increase in p16 expression was seen in 6 (86%) of the 7 cases with noninvasive carcinoma, although a loss of p16 immunoexpression was seen in the invasive carcinoma component in 3 (75%) of the 4 cases. This study demonstrated that seborrheic keratosis can undergo malignant transformation, particularly in large-sized lesions in elderly patients. Malignant components mimic porocarcinoma or inverted follicular keratosis. Malignant transformation induced by TP53 and PTEN mutations and tumor invasion by CDKN2A inactivating mutations are suggested in this study.

Bacterial taxa predictive of hyperpigmented skins

Background and Aims

Dark spots, brown spots, or hyperpigmented spots (HPS) are oval or irregular brown areas of skin. Their emergence is associated with dysregulation of the immune system, and may also be caused by a deficiency in stromal cell‐derived factor‐1, leading to perturbed melanogenesis and accumulation of melanosomes within neighboring keratinocytes. The skin microbiota (living microorganisms present on the surface of the skin) is known to play essential roles in maintaining skin homeostasis and in regulating the immune system. Here, we investigated whether the microbiota could play a role in the emergence of HPS.

Methods

The clinical study involved 38 European women, selected from among 74 volunteers. Participants were divided into two groups depending on the spot areas measured on their faces. The study was designed to avoid conflicting factors: both groups presented similar skin pH, hydration, transepidermal water loss, and sebum levels. The two cohorts were also age‐matched, with a mean of 29‐years‐old for both.

Results

Alpha‐diversity of the microbiota was similar for the two groups. On skins with more HPS, seven bacterial genera were identified in significantly higher proportions and included opportunistic pathogens and inflammatory bacteria. Six bacterial genera, including bacteria showing antioxidant and anti‐UV properties, were identified in significantly higher proportions on less spotted skins. Cross‐domain association networks revealed distinct co‐occurrences of genera between the two groups, suggesting nonidentical community structures and exchanges, depending on the HPS status.

Conclusion

Our results reveal specific microbiota composition and networks on skins based on HPS status. Changes could alter communication with the immune system, leading to the emergence of dark spots. As an essential part of the overall skin ecosystem, and through its interaction with the skin matrix, the skin microbiota and its maintenance could be considered a new target for skincare applications.

Three-dimensional histological explanation of the dermoscopy patterns in acral melanocytic lesions

Dermoscopic images of pigmented lesions have distinct features on the sole where skin ridges and furrows exist. Pigmentation of benign nevus usually locates on the skin furrow, while the malignant melanoma is pigmented on the skin ridge. Correspondence between dermoscopy and pathology in the pigmented lesions on soles have been studied based on conventional vertical pathological images. However, for the full understanding of the correspondence, observation of horizontal histological images would be required, because the epidermis constructs unique horizontal structures, namely crista profunda limitans, crista profunda intermedia, and transverse ridge. In this study, we analyzed basic dermoscopic images of the representative acral melanocytic lesions (nevus, lentigo, and malignant melanoma) by horizonal histological images. We created serial horizontal pathological images by digital reconstruction of a hundred of serial vertical images. We could show that parallel furrow pattern is created by the pigmentation of crista profunda limitans, parallel ridge pattern by the pigmentation of both of crista profunda limitans and crista profunda intermediate, and lattice-like pattern by the pigmentation of transverse ridge. Our results would be useful for the intuitive histological understanding of dermoscopy.

Defining the Molecular Genetics of Dermoscopic Naevus Patterns

Melanocytic naevi are common melanocytic proliferations that may simulate the appearance of cutaneous melanoma. Naevi commonly harbour somatic mutations implicated in melanomagenesis but in most cases lack the necessary genomic alterations required for melanoma development. While the mitogen-activated protein kinase pathway and ultraviolet radiation strongly contribute to naevogenesis, the somatic mutational landscape of dermoscopic naevus subsets distinguishes some of the molecular hallmarks of naevi in relation to melanoma. We herein discuss the classification of naevi and theories of naevogenesis and review the current literature on the somatic alterations in naevi and melanoma. This review focusses on the clinical-dermoscopic-pathological and genomic correlation of naevi that shapes the current understanding of naevi.

Improving classification of melanocytic nevi: Association of BRAF V600E expression with distinct histomorphologic features

BACKGROUND

A subset of melanomas carrying a B-Raf proto-oncogene, serine/threonine kinase gene (BRAF) V600E mutation, which is the most common targetable mutation in melanoma, arise in association with a melanocytic nevus that is also harboring a BRAF V600E mutation. The detailed histomorphologic characteristics of nevi positive for BRAF V600E have not been systematically documented.

OBJECTIVE

To identify histomorphologic features correlating with BRAF V600E status in nevi.

METHODS

We retrospectively identified melanocytic nevi from our laboratory reporting system. We performed a histomorphologic analysis and analysis of BRAF V600E expression by immunohistochemistry.

RESULTS

Thirteen nevi (14.8%) were negative and 76 (86.4%) were positive for BRAF V600E. The nevi positive for BRAF V600E were predominantly dermal (predominantly dermal growth in 55.3% of nevi positive for BRAF V600E and 15.4% of nevi negative for BRAF V600E [P = .01]) and showed a congenital growth pattern (congenital growth pattern in 51.3% of nevi positive for BRAF V600E and 15.4% of nevi negative for BRAF V600E [P = .02]). Compared with nevi negative for BRAF V600E, those that were positive for BRAF V600E often exhibited predominantly nested intraepidermal melanocytes, larger junctional nests, abrupt lateral circumscription, and larger cell size. Architectural disorder and inflammatory infiltrates were seen more often in nevi negative for BRAF V600E. BRAF sequencing of a subset of nevi confirmed the immunohistochemical results.

LIMITATIONS

Limitations include the study's retrospective design and the small sample size of nevi negative for BRAF V600E.

CONCLUSIONS

BRAF V600E is associated with distinct histomorphologic features in nevi. These features may contribute to improving the accuracy of classification and diagnosis of melanocytic neoplasms.

Melanocytic nevi and melanoma: unraveling a complex relationship

Approximately 33% of melanomas are derived directly from benign, melanocytic nevi. Despite this, the vast majority of melanocytic nevi, which typically form as a result of BRAF^V600E-activating mutations, will never progress to melanoma. Herein, we synthesize basic scientific insights and data from mouse models with common observations from clinical practice to comprehensively review melanocytic nevus biology. In particular, we focus on the mechanisms by which growth arrest is established after BRAF^V600E mutation. Means by which growth arrest can be overcome and how melanocytic nevi relate to melanoma are also considered. Finally, we present a new conceptual paradigm for understanding the growth arrest of melanocytic nevi in vivo termed stable clonal expansion. This review builds upon the canonical hypothesis of oncogene-induced senescence in growth arrest and tumor suppression in melanocytic nevi and melanoma.

PI3K Signaling in Tissue Hyper-Proliferation: From Overgrowth Syndromes to Kidney Cysts

The members of the PhosphoInositide-3 Kinase (PI3K) protein family are well-known regulators of proliferative signals. By the generation of lipid second messengers, they mediate the activation of AKT/PKB (AKT) and mammalian Target Of Rapamycin (mTOR) pathways. Although mutations in the PI3K/AKT/mTOR pathway are highly characterized in cancer, recent evidence indicates that alterations in the proliferative signals are major drivers of other diseases such as overgrowth disorders and polycystic kidney disease. In this review, we briefly summarize the role of the PI3K/AKT/mTOR pathway in cell proliferation by comparing the effect of alterations in PI3K enzymes in different tissues. In particular, we discuss the most recent findings on how the same pathway may lead to different biological effects, due to the convergence and cooperation of different signaling cascades.

Genetics of melanocytic nevi

Melanocytic nevi are a benign clonal proliferation of cells expressing the melanocytic phenotype, with heterogeneous clinical and molecular characteristics. In this review, we discuss the genetics of nevi by salient nevi subtypes: congenital melanocytic nevi, acquired melanocytic nevi, blue nevi, and Spitz nevi. While the molecular etiology of nevi has been less thoroughly studied than melanoma, it is clear that nevi and melanoma share common driver mutations. Acquired melanocytic nevi harbor oncogenic mutations in BRAF, which is the predominant oncogene associated with melanoma. Congenital melanocytic nevi and blue nevi frequently harbor NRAS mutations and GNAQ mutations, respectively, while Spitz and atypical Spitz tumors often exhibit HRAS and kinase rearrangements. These initial 'driver' mutations are thought to trigger the establishment of benign nevi. After this initial phase of the cell proliferation, a senescence program is executed, causing termination of nevi growth. Only upon the emergence of additional tumorigenic alterations, which may provide an escape from oncogene-induced senescence, can malignant progression occur. Here, we review the current literature on the pathobiology and genetics of nevi in the hope that additional studies of nevi promise to inform our understanding of the transition from benign neoplasm to malignancy.

Melanocytic naevi with globular and reticular dermoscopic patterns display distinct BRAF V600E expression profiles and histopathological patterns

BACKGROUND

BRAF (v-raf murine sarcoma viral oncogene homologue B) V600E mutations have been detected with high frequency in melanocytic naevi. Few studies have stratified analyses by naevus dermoscopic pattern.

OBJECTIVES

To determine the frequency of BRAF V600E expression and histopathological pattern in acquired melanocytic naevi distinguished by a globular vs. reticular dermoscopic pattern.

METHODS

We retrospectively identified histologically proven melanocytic naevi with banal reticular or globular dermoscopic patterns and evaluated BRAF V600E expression using immunohistochemistry.

RESULTS

BRAF V600E expression was detected in 11 of 12 globular naevi vs. four of 13 reticular naevi (91·7% vs. 30·1%, P = 0·004). A predominantly dermal growth pattern (P < 0·001) and the presence of large junctional nests (P = 0·017) were each associated with a globular dermoscopic pattern. The presence of either a predominantly dermal growth pattern or large junctional nests was found in 13 of 15 naevi positive for BRAF V600E and in two of 10 naevi negative for BRAF V600E (86·7% vs. 20%, P = 0·002).

CONCLUSIONS

The frequency of BRAF V600E mutations differs in naevi distinguished by unique dermoscopic structures and microanatomical growth patterns. Globular naevi, which most often histologically correspond to a predominantly dermal growth pattern and/or the presence of large junctional nests, are significantly more likely to express BRAF V600E than reticular naevi. These preliminary results require validation, but may directly inform future studies of naevogenesis and melanoma genesis.