Distinct Regulation of EZH2 and its Repressive H3K27me3 Mark in Polyomavirus-Positive and -Negative Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an aggressive skin cancer for which Merkel cell polyomavirus integration and expression of viral oncogenes small T and Large T have been identified as major oncogenic determinants. Recently, a component of the PRC2 complex, the histone methyltransferase enhancer of zeste homolog 2 (EZH2) that induces H3K27 trimethylation as a repressive mark has been proposed as a potential therapeutic target in MCC. Because divergent results have been reported for the levels of EZH2 and trimethylation of lysine 27 on histone 3, we analyzed these factors in a large MCC cohort to identify the molecular determinants of EZH2 activity in MCC and to establish MCC cell lines' sensitivity to EZH2 inhibitors. Immunohistochemical expression of EZH2 was observed in 92% of MCC tumors (156 of 170), with higher expression levels in virus-positive than virus-negative tumors (P = 0.026). For the latter, we showed overexpression of EZHIP, a negative regulator of the PRC2 complex. In vitro, ectopic expression of the large T antigen in fibroblasts led to the induction of EZH2 expression, whereas the knockdown of T antigens in MCC cell lines resulted in decreased EZH2 expression. EZH2 inhibition led to selective cytotoxicity on virus-positive MCC cell lines. This study highlights the distinct mechanisms of EZH2 induction between virus-negative and -positive MCC.

Distinct regulations driving YAP1 expression loss in poroma, porocarcinoma and RB1-deficient skin carcinoma

AIMS

Recently, YAP1 fusion genes have been demonstrated in eccrine poroma and porocarcinoma, and the diagnostic use of YAP1 immunohistochemistry has been highlighted in this setting. In other organs, loss of YAP1 expression can reflect YAP1 rearrangement or transcriptional repression, notably through RB1 inactivation. In this context, our objective was to re-evaluate the performance of YAP1 immunohistochemistry for the diagnosis of poroma and porocarcinoma.

METHODS AND RESULTS

The expression of the C-terminal part of the YAP1 protein was evaluated by immunohistochemistry in 543 cutaneous epithelial tumours, including 27 poromas, 14 porocarcinomas and 502 other cutaneous tumours. Tumours that showed a lack of expression of YAP1 were further investigated for Rb by immunohistochemistry and for fusion transcripts by real-time PCR (YAP1::MAML2 and YAP1::NUTM1). The absence of YAP1 expression was observed in 24 cases of poroma (89%), 10 porocarcinoma (72%), 162 Merkel cell carcinoma (98%), 14 squamous cell carcinoma (SCC) (15%), one trichoblastoma and one sebaceoma. Fusions of YAP1 were detected in only 16 cases of poroma (n = 66%), 10 porocarcinoma (71%) all lacking YAP1 expression, and in one sebaceoma. The loss of Rb expression was detected in all cases except one of YAP1-deficient SCC (n = 14), such tumours showing significant morphological overlap with porocarcinoma. In-vitro experiments in HaCat cells showed that RB1 knockdown resulted in repression of YAP1 protein expression.

CONCLUSION

In addition to gene fusion, we report that transcriptional repression of YAP1 can be observed in skin tumours with RB1 inactivation, including MCC and a subset of SCC.

[Multifocal vulvar pigmentation: Don't ignore a rare diagnosis]

Vulvar melanoma is a rare tumour, of poorly known pathogenesis, which presents particularities compared to cutaneous melanoma: more frequently achromic and very often multifocal, it is of the lentiginous histological type (MLM), with in half of the cases lentiginous melanocytic hyperplasia at a distance.

Histopathologic Features of Chilblainlike Lesions Developing in the Setting of the Coronavirus Disease 2019 (COVID-19) Pandemic

CONTEXT.—

During the coronavirus disease 2019 pandemic, several studies have described a distinctive cutaneous manifestation with a clinical picture resembling chilblains or chilblain lupus in young patients.

OBJECTIVE.—

To report the histopathologic description of a series of chilblainlike lesions appearing in the context of the severe acute respiratory syndrome coronavirus 2 epidemic.

DESIGN.—

The study included 13 patients with cutaneous acral lesions resembling chilblains occurring in the setting of suspected severe acute respiratory syndrome coronavirus 2 infection with available skin biopsy.

RESULTS.—

Two main histopathologic patterns were observed: a chilblainlike histopathologic pattern (10 of 13 cases; 77%) and a thrombotic vasculopathy pattern (3 of 13 cases; 23%). The chilblainlike histopathologic pattern featured a superficial and deep perivascular infiltrate of lymphocytes of varying intensity. This infiltrate was sometimes peri-eccrine and alterations of eccrine glands were present in most cases. Vacuolar alteration of the basal layer of the epidermis was found in a majority of patients. Lichenoid interface dermatitis was rarely present. The thrombotic vasculopathy pattern featured an absent or mild inflammatory infiltrate, multiple intraluminal fibrin thrombi, and ischemic epidermal necrosis. In both patterns, no true vasculitis was observed. No patient tested positive for severe acute respiratory syndrome coronavirus 2 by polymerase chain reaction, possibly because these lesions may represent late cutaneous manifestations of the disease or are associated with an early effective immune response.

CONCLUSIONS.—

The relationship of chilblainlike lesions to severe acute respiratory syndrome coronavirus 2 requires further investigations. Histopathologic features mimic chilblains, chilblain lupus, and, less frequently, a thrombotic vasculopathy. Response to viral infection might trigger diverse mechanisms leading to the 2 histopathologic patterns described.

Successful Treatment of Generalized Eruptive Keratoacanthoma of Grzybowski with Acitretin

Introduction

Keratoacanthomas (KA) are common cutaneous skin tumors originating from the hair follicles. Unlike squamous cell carcinoma, KA can regress spontaneously and have a benign evolution. Solitary KA is the most common form but familial multiple KA (Ferguson–Smith type), genetically predisposed KA (such as in xeroderma pigmentosum, or Muir–Torre syndrome), or sporadic multiple eruptive KA (Grzybowski type) have been described. Generalized eruptive KA of Grzybowski (GEKA) is a rare condition (around 40 reported cases). The pathophysiology is still unclear. Human papillomavirus (HPV) has been detected in sporadic KA but the presence of HPV39 has never been reported, to our knowledge, in GEKA.

Case Report

GEKA in an 80-year-old woman was successfully treated with acitretin (0.5 mg/kg/day) combined with surgical removal of the largest lesions. Treatment was well tolerated and led to decreased pruritus and tumor regression within 6 months. The presence of HPV39 was detected in a lesion by polymerase chain reaction and Sanger sequencing. No genetic alteration was found, in particular in the genes usually altered in squamous cell carcinoma (including NOTCH1, NOTCH2, CDKN2A, TP53).

Conclusion

We report a case of GEKA associated with the presence of HPV39 and the successful use of acitretin combined with surgical removal of the larger lesions.

Neutrophilic eccrine hidradenitis in two patients treated with BRAF inhibitors: a new cutaneous adverse event

Neutrophilic eccrine hidradenitis (NEH) is a rare neutrophilic dermatosis, first described in patients undergoing chemotherapy for a malignant haemopathy. It has polymorphous clinical features and the association of both clinical and histological features is necessary to make a diagnosis. We report the first two cases of NEH in patients treated with a BRAF inhibitor (BRAFi), either dabrafenib or vemurafenib, for a stage IV metastatic melanoma. Disseminated erythematous plaques associated with fever and polyarthralgia occurred early after the initiation of treatment and were badly tolerated. Histological analyses confirmed the diagnosis of NEH. Symptoms disappeared a few days after the cessation of treatment and introduction of topical steroids. The replacement of one BRAFi with another is a therapeutic alternative as it is not necessarily associated with a relapse of NEH. NEH can be added to the spectrum of neutrophilic dermatoses induced by BRAFis. It occurs earlier (3-4 days) than previously described drug-induced NEH (9-12 days) and may be an earlier stage of eccrine squamous syringometaplasia, which has already been reported in the context of BRAFi-treated patients.

Sarcoidosis in Patients Treated with Vemurafenib for Metastatic Melanoma: A Paradoxical Autoimmune Activation

BACKGROUND

Vemurafenib, a BRAF inhibitor, is a first-line treatment for inoperable melanoma. Sarcoidosis has never been reported in patients on vemurafenib.

OBJECTIVES

We describe 5 cases of sarcoidosis in patients treated with vemurafenib.

METHODS

Seventy patients receiving vemurafenib for a BRAF-mutated inoperable stage III or IV melanoma were treated in our centre.

RESULTS

Five patients (7.1%) developed sarcoidosis or a sarcoid-like reaction on vemurafenib; 4 patients had cutaneous signs and 3 had extracutaneous disorders (bilateral hilar lymph nodes, uveitis). Histological analysis of skin lesions revealed epithelioid granulomas without necrosis, consistent with sarcoidosis. Angiotensin-converting enzyme levels were high in 2 patients. Cutaneous and ophthalmological lesions rapidly disappeared on topical corticosteroid treatment without the cessation of vemurafenib treatment. Complete remission of melanoma was observed in 3 patients and partial remission was observed in another.

CONCLUSION

BRAF inhibitors probably have immune system-enhancing effects and should therefore be recognized as potential inducers of sarcoidosis.

The Great Imitator in Endocrinology: A Painful Hypophysitis Mimicking a Pituitary Tumor

CONTEXT

The incidence of syphilis has been increasing in recent decades in Western countries. Pituitary involvement is very unusual in syphilis. This infectious disease is not often considered in the workup of a patient with hypophysitis.

CASE

We report the case of a 28-year-old man who was admitted for headaches worsening over 1 month that became resistant to paracetamol. A magnetic resonance imaging scan revealed a heterogeneous pituitary mass suggesting a pituitary tumor. Hormonal investigations showed partial corticotropic and thyrotropic deficiencies. Headaches required high doses of morphine. Transsphenoidal surgery was performed, and histological examination revealed an aspect of hypophysitis. One month later, clinical reexamination showed skin and tongue lesions very suggestive of a syphilis infection, which was serologically confirmed. Immunohistochemistry on paraffin sections of the resected pituitary revealed an abundant presence of Treponema pallidum, confirming the diagnosis of a syphilitic hypophysitis. Intravenous therapy by benzylpenicillin for 14 days was rapidly efficient. Headaches stopped within a few days, and the skin and tongue lesions disappeared during the following month. Thyrotropic deficiency resolved in 2 weeks, but partial corticotropic deficiency persisted at 3 months.

CONCLUSION

This is the first case of a pituitary involvement in acquired syphilis, pathologically proven, in a non-HIV-infected patient. In a context of the resurgence of syphilis, this diagnosis should be considered in the case of a pituitary lesion with unusually intense headaches.

Atypical fibrous histiocytoma of the skin with CD30 and p80/ALK1 positivity and ALK gene rearrangement

We report the case of a two patients who presented with a solitary, asymptomatic, angiomatoid nodule on the right thigh. Histopathological finding showed a poorly circumscribed lesion, located in the dermis. The morphological aspect strongly suggested the diagnosis of atypical fibrous histiocytoma (AFH), but surprisingly, the neoplastic cells were diffusely CD30+, with a membrane staining devoid of paranuclear dot. The lesions were tested for p80/ALK1 expression. Surprisingly, we found a diffuse cytoplasmic positivity. Interestingly, using break-apart fluorescent in situ hybridization (FISH), we evidenced an ALK rearrangement in nearly 50% of the neoplastic cells. The expression of CD30 and ALK1 with ALK gene rearrangement raised the possibility of three diagnoses: a primary cutaneous anaplastic large cell lymphoma (ALCL), a cutaneous inflammatory myofibroblastic tumor (IMT), an AFH of the skin associated with ALK gene rearrangement and CD30 positivity. The three hypotheses were discussed and finally, although p80/ALK1 expression and cytogenetic abnormalities in fibrous histiocytoma (FH) are not yet reported to the best of our knowledge, we favored the diagnosis of AFH.