The diagnostic utility of Merkel cell polyoma virus immunohistochemistry in cytology specimens

OBJECTIVE

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine neoplasm that predominantly affects elderly and immunocompromised patients. Merkel cell polyoma virus (MCPyV) is clonally integrated into the majority of MCCs and has been linked to patient outcomes, playing a central role in the pathogenesis of the disease. We aimed to assess the utility of MCPyV immunohistochemistry (IHC) in the diagnosis of MCC in cytology cell block specimens and correlating with clinicopathologic features.

METHODS

Fifty-three cytology samples of MCC with sufficient cell block material were stained for MCPyV by IHC and scored semi-quantitatively in extent and intensity. Morphologic mimics of MCC including small cell lung carcinoma (n = 10), non-Hodgkin lymphoma (n = 10), basaloid squamous cell carcinoma (n = 6) and other neuroendocrine carcinomas (n = 8) were stained in parallel. Positive staining was defined as >1% of the tumour cells showing at least moderate staining intensity.

RESULTS

The cytologic features of MCC were characterized by high nuclear-cytoplasmic ratios, hyperchromatic nuclei with 'salt and pepper' chromatin, and nuclear moulding. MCPyV was detected in 24 of 53 cases (45%). Staining was strong and diffuse in roughly half of the positive samples. Of the morphologic mimics, one follicular lymphoma showed strong and diffuse staining. In contrast to prior studies, we saw no association between MCPyV status and patient outcomes.

CONCLUSION

Merkel cell polyoma virus IHC is highly specific (97%) for the diagnosis of MCC in our cohort, and can serve as a useful diagnostic tool for distinguishing MCC for morphologic mimics.

Metastatic Merkel Cell Carcinoma After Simultaneous Pancreas-Kidney Transplantation: Fatal Outcomes

Merkel cell carcinoma (MCC) is a rare, highly aggressive cutaneous malignancy. Immunosuppression increases the risk of MCC and is associated with poor prognosis. Organ transplant recipients (OTR) have worse overall survival (OS) than patients with immunosuppression due to other causes. Treating MCC after organ transplantation is challenging, as checkpoint inhibitor immunotherapy, the standard of care for treating MCC, increases the risk of transplant rejection. This paper reviews the cases of two simultaneous pancreas-kidney transplant (SPKT) recipients with MCC and explores the role of immunosuppression in the development of MCC. Immunosuppression was discontinued and checkpoint inhibitor therapy was initiated in the first patient and considered by the second patient. In both cases, treatment failed, and the patients died shortly after developing metastatic MCC. These cases illustrate the need for improved multidisciplinary treatment regimens for MCC in OTRs. J Drugs Dermatol. 2024;23(5):376-377.     doi:10.36849/JDD.8234  .

Merkel cell carcinoma overlapping Bowen's disease: two cases report and literature review

PURPOSE

Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin, which mainly occurs in the sun exposed sites of white patients over 65 years, with a higher recurrence and metastasis rate. Clinically, MCC overlapping Bowen's disease (BD) is a very rare subtype of MCC. Few cases in the literature have been described and the management is not well defined. We summarize and update the epidemiology, clinical and histopathological features, metastasis characteristics, local recurrence rate and management of it by presenting two cases of MCC overlapping BD and reviewing the literature over the last 11 years.

DESIGN

We consulted databases from PubMed, ResearchGate and Google Scholar by MeSh "Merkel cell carcinoma" and "Bowen's disease", "Bowen disease" or "squamous cell carcinoma in situ", from January 2013 to December 2023 and reviewed the literatures. We reported two additional cases.

RESULTS

Total 13 cases of MCC overlapping BD were retrospectively analyzed, in whom mainly in elderly women over 70 years, the skin lesions were primarily located on the faces, followed by the extremities and trunk. Most of them were asymptomatic, firm, dark red nodules arising on rapidly growing red or dark brown patches, or presenting as isolated nodules. Dermoscopy evaluation was rarely performed in the pre-operative diagnostic setting. All cases were confirmed by histopathology and immunohistochemistry. The most definitive treatment was extended local excision, but local recurrences were common. Of the 13 cases, 4 cases experienced local or distant metastasis. One suffered from an in-transit recurrence of MCC on the ipsilateral leg after local excision and lymph node dissection, whose metastasis completely subsided after avelumab treatment and without recurrence or metastasis during 6 months of follow-up.

CONCLUSIONS

MCC overlapping BD is a very rare skin tumor mainly predisposed on the faces, with high misdiagnosis rate and recurrence rate. Advanced disease at diagnosis is a poor prognostic factor, suggesting that earlier detection may improve outcome. The acronym, AEIOUN, has been proposed to aid in clinical identification. Our reports and the literature review can provide a better awareness and management of it.

Systematic evaluation of Merkel cell carcinoma clinical practice guidelines using the AGREE II instrument

Merkel cell carcinoma (MCC) is a rare type of skin cancer that requires a multidisciplinary approach with a variety of specialists for management and treatment. Clinical practice guidelines (CPGs) have recently been established to standardize management algorithms. The objective of this study was to appraise such CPGs via the Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument. Eight CPGs were identified via systematic literature search following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. Four appraisers trained in AGREE II protocols evaluated each CPG and deemed two CPGs as high quality, five as moderate quality, and one as low quality. Intraclass correlation coefficients (ICCs) were calculated to verify reviewer consistency as excellent, good, and moderate across four, one, and one domain, respectively. The majority of MCC CPGs are lacking in specifying stakeholder involvement, applicability, and rigor of development. The two high quality CPGs are from the Alberta Health Services (AHS) and the collaboration between the European Dermatology Forum, the European Association of Dermato-Oncology, and the European Organization of Research and Treatment of Cancer (EDF/EADO/EORTC). The EDF/EADO/EORTC CPG had the highest overall score with no significant deficiencies across any domain. An important limitation is that the AGREE II instrument is not designed to evaluate the validity of each CPG's recommendations; conclusions therefore can only be drawn about each CPG's developmental quality. Future MCC CPGs may benefit from garnering public perspectives, inviting external expert review, and considering available resources and implementation barriers during their developmental stages.

Unusual Metastasis to Eyelid from Extraocular Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is an unusual skin tumor that has a significant rate of distant and local metastases. It is known that primary MCC of the eyelid usually occurs at the upper eyelid. Here we report an unusual case of MCC metastasis to the eyelid. A 63-year-old male was diagnosed with MCC three years earlier after initially presenting with a mass in his right thigh. After histopathological diagnosis, the patient received medical therapy. During treatment, he developed multiple distant metastases and a firm, purple, vascularized lesion on the upper eyelid. We confirmed the lesion was an eyelid metastasis of MCC by histopathological examination and imaging methods. This case shows that extraocular MCC can metastasize to the eyelids, particularly the upper eyelid, where primary periocular MCC usually appears.

SATB2, CKAE1/AE3, and synaptophysin as a sensitive immunohistochemical panel for the detection of lymph node metastases of Merkel cell carcinoma

Histopathological evaluation of lymph nodes in Merkel cell carcinoma has become crucial in progression estimation and treatment modification. This study was undertaken to determine the most sensitive immunohistochemical panel for detecting MCC nodal metastases. We included 56 patients with 102 metastatic MCC lymph nodes, which were tested with seven antibodies: cytokeratin (CKAE1/AE3), CK20, chromogranin A, synaptophysin, INSM1, SATB2, and neurofilament (NF). Tissue microarrays (TMA) composed of 2-mm tissue cores from each nodal metastasis were constructed. A semiquantitative 5-tier scoring system (0%, < 25%, 25-74%, 75-99%, 100% positive MCC cells with moderate to strong reactivity) was implemented. In the statistical assessment, we included Merkel cell polyomavirus (MCPyV) status and expression heterogeneity between lymph nodes from one patient. A cumulative percentage of moderate to strong expression ≥ 75% of tumoral cells was observed for single cell markers as follows: 91/102 (89.2%) SATB2, 85/102 (83%) CKAE1/AE3, 80/102 (78.4%) synaptophysin, 75/102 (75.5%) INSM1, 68/102 (66.7%) chromogranin A, 60/102 cases (58.8%) CK20, and 0/102 (0%) NF. Three markers presented a complete lack of immunoreactivity: 8/102 (7.8%) CK20, 7/102 (6.9%) chromogranin A, and 6/102 (5.9%) NF. All markers showed expression heterogeneity in lymph nodes from one patient; however, the most homogenous was INSM1. The probability of detecting nodal MCC metastases was the highest while using SATB2 as a first-line marker (89.2%) with subsequential adding CKAE1/AE3 (99%); these results were independent of MCPyV status. Synaptophysin showed a superior significance in confirming the neuroendocrine origin of metastatic cells. This comprehensive analysis allows us to recommend simultaneous evaluation of SATB2, CKAE1/AE3, and synaptophysin in the routine pathologic MCC lymph node protocol.

Merkel cell carcinoma recurrence risk estimation is improved by integrating factors beyond cancer stage: A multivariable model and web-based calculator

BACKGROUND

Merkel cell carcinoma (MCC) recurs in 40% of patients. In addition to stage, factors known to affect recurrence risk include: sex, immunosuppression, unknown primary status, age, site of primary tumor, and time since diagnosis.

PURPOSE

Create a multivariable model and web-based calculator to predict MCC recurrence risk more accurately than stage alone.

METHODS

Data from 618 patients in a prospective cohort were used in a competing risk regression model to estimate recurrence risk using stage and other factors.

RESULTS

In this multivariable model, the most impactful recurrence risk factors were: American Joint Committee on Cancer stage (P < .001), immunosuppression (hazard ratio 2.05; P < .001), male sex (1.59; P = .003) and unknown primary (0.65; P = .064). Compared to stage alone, the model improved prognostic accuracy (concordance index for 2-year risk, 0.66 vs 0.70; P < .001), and modified estimated recurrence risk by up to 4-fold (18% for low-risk stage IIIA vs 78% for high-risk IIIA over 5 years).

LIMITATIONS

Lack of an external data set for model validation.

CONCLUSION/RELEVANCE

As demonstrated by this multivariable model, accurate recurrence risk prediction requires integration of factors beyond stage. An online calculator based on this model (at merkelcell.org/recur) integrates time since diagnosis and provides new data for optimizing surveillance for MCC patients.

Neoadjuvant PD-1 Inhibitors: A Tale of Two Cases

Treatment responses for locally advanced cutaneous squamous cell carcinoma (cSCC) and Merkel cell carcinoma (MCC) are often short lived and are marred with recurrences. The introduction of adjuvant PD-1 inhibitors has demonstrated significant improvement in both, response rates, and duration of response. For patients with high-risk resectable disease, adjuvant treatments have not demonstrated an ability to reduce recurrence risk. However, there is an opportunity in the neoadjuvant setting to alter recurrence risk. Here we dem-onstrate two cases of neoadjuvant treatment of cSCC and MCC with impressive results.  J Drugs Dermatol. 2024;23(2):     doi:10.36849/JDD.7043e.

NCCN Guidelines® Insights: Merkel Cell Carcinoma, Version 1.2024

The NCCN Guidelines for Merkel Cell Carcinoma (MCC) provide recommendations for diagnostic workup, clinical stage, and treatment options for patients. The panel meets annually to discuss updates to the guidelines based on comments from expert review from panel members, institutional review, as well as submissions from within NCCN and external organizations. These NCCN Guidelines Insights focus on the introduction of a new page for locally advanced disease in the setting of clinical node negative status, entitled "Clinical N0 Disease, Locally Advanced MCC." This new algorithm page addresses locally advanced disease, and the panel clarifies the meaning behind the term "nonsurgical" by further defining locally advanced disease. In addition, the guideline includes the management of in-transit disease and updates to the systemic therapy options.

A Challenging Diagnosis of Merkel Cell Carcinoma Occurring in the Lymph Nodes and Skin of a Patient with Mantle Cell Lymphoma: A Case Report

Abstract is missing (Short communication)

Exploring diagnosis and therapeutic complexities of an aggressive Merkel cell carcinoma: A case report and review of the literature

Merkel cell carcinoma (MCC) is an aggressive and rare cutaneous neuroendocrine carcinoma that predominantly affects the sun-damaged skin of the head and neck region, extremities, and trunk of older white individuals. Microscopically, MCC is characterized by nests or sheets of uniform small round blue cells with scant cytoplasm, granular nuclei with a salt-and-pepper chromatin pattern, high proliferative activity, and occasional necrosis. They are usually positive for epithelial and neuroendocrine markers, particularly for cytokeratin 20 and AE1/AE3 in a paranuclear dot-like staining. We herein contribute by reporting a case of MCC affecting the auricular pavilion of a 66-year-old female patient from Campinas, Brazil. Additionally, a review of the current literature is also included to analyze all the cases that have been reported in the English-language literature, totalizing 27 cases of MCC on the external ear. The 5-year overall survival rate for individuals with localized MCC is 50% and the most common treatment choice is the combination of surgery with adjuvant radiotherapy and sentinel lymph node biopsy.

Merkel Cell Carcinoma of Unknown Primary Origin

Merkel cell carcinoma (MCC) is a rare and highly aggressive primary cutaneous neuroendocrine carcinoma most often occurring in the elderly. Risk factors include chronic sun exposure and immunosuppression (1). MCC is associated with frequent recurrences and a high metastatic potential and mortality rate (1). It is the second most common cause of skin-cancer-related death after melanoma. At primary diagnosis with an apparent cutaneous tumor, loco-regional metastases are present in up to 30% of patients, and 6-12% have distant metastatic disease (2-3). Up to 5% of cases present with unknown primary origin (4). Five-year overall survival for patients with advanced or metastatic disease is 13-18% (4). We report two cases of MCC presenting without primary cutaneous involvement; first at an unusual location in the adipose tissue of the right breast, and the second one with only a clinically positive left inguinal lymph node. In October 2018, a 78-year-old woman presented with a 15-week history of a painless solitary mass in the upper outer quadrant (UOQ) of the right breast with no visible cutaneous involvement. Her medical history included hypertension, dyslipidemia, and plaque psoriasis. She underwent ultrasound guided biopsy, and histopathology confirmed the diagnosis of metastatic MCC (mMCC). Positron emission tomography/computed tomography (PET/CT) scans showed increased standardized uptake values in the mass in the UOQ and an additional mass in the lower inner quadrant (Figure 1A). The patient underwent mastectomy and lymph node dissection of the right axilla. Histopathology confirmed mMCC and negative axillary lymph nodes. Regular follow-up (clinical examination, PET/CT scan, ultrasound, mammography) every 6 months revealed no disease recurrence during this 4-year period (Figure 1B). In September 2021, a 66-year-old man was referred to our Clinic with clinically detectable painful left inguinal lymphadenopathy. Excisional biopsy was performed, and histopathology confirmed the diagnosis of mMCC (Figure 2). After an extensive clinical and imaging evaluation (PET/CT scan), which confirmed disseminated disease (Figure 3A), initial treatment with the programmed cell death ligand 1 inhibitor (anti PD-L1) avelumab was proposed. The first cycle consisting of seven intravenous applications, and was applied in October 2021. After one year and completion of the third cycle of therapy, imaging assessment (PET-CT scan) detected a solitary lesion in the pancreas. Fine needle aspiration biopsy confirmed a distant metastasis of MCC that was later treated with stereotactic radiosurgery. The fourth cycle of immunotherapy was completed in March 2023. No treatment-related adverse events were noted during these 18 months of follow-up. Recent PET/CT scans demonstrated scaring tissue in the pancreas with no signs of locoregional or distant metastatic disease (Figure 3B). Management of MCC should be individualized based on the specific pattern of disease presentation. The presence of nodal disease is one of the most powerful predictors of overall survival and risk for developing distant metastatic disease (3-4). Multidisciplinary tumor board discussions are mandatory for the management of advanced MCC. New emerging treatment options have once again returned focus to this rare and highly-aggressive entity. Until recent years, mMCC was managed with extensive surgery, radiotherapy, or chemotherapy, but responses were not durable (1). Based on new clinical trials, immunotherapy has now become a rational and promising treatment option and is considered as first-line treatment in patients with advanced MCC (5). The management of patients with MCC of unknown primary origin should adhere to that for patients with an identifiable primary tumour (6). Although cutaneous manifestations are the hallmark of MCC, only a minority of cases have been reported in the literature without any cutaneous involvement (7-10). Our cases highlight this unusual presentation of MCC that could be misleading and contribute to delayed diagnosis. We therefore emphasize the importance of considering rare forms of malignancies such as MCC even in the absence of a primary cutaneous lesion.

Risk of Multiple Primary Cancers in Patients With Merkel Cell Carcinoma: A SEER-Based Analysis

Importance

The risk of subsequent primary cancers after a diagnosis of cutaneous Merkel cell carcinoma (MCC) is not well established.

Objective

To evaluate the risk of subsequent primary cancers after the diagnosis of a first primary cutaneous MCC.

Design, Setting, and Participants

This cohort study analyzed data from 17 registries of the Surveillance, Epidemiology, and End Results (SEER) Program from January 1, 2000, to December 31, 2019. In all, 6146 patients diagnosed with a first primary cutaneous MCC were identified.

Main Outcomes and Measures

The primary outcome was the relative and absolute risks of subsequent primary cancers after the diagnosis of a first primary MCC, which were calculated using the standardized incidence ratio (SIR; ratio of observed to expected cases of subsequent cancer) and the excess risk (difference between observed and expected cases of subsequent cancer divided by the person-years at risk), respectively. Data were analyzed between January 1, 2000, and December 31, 2019.

Results

Of 6146 patients with a first primary MCC diagnosed at a median (IQR) age of 76 (66-83) years, 3713 (60.4%) were men, and the predominant race and ethnicity was non-Hispanic White (5491 individuals [89.3%]). Of these patients, 725 (11.8%) developed subsequent primary cancers, with an SIR of 1.28 (95% CI, 1.19-1.38) and excess risk of 57.25 per 10 000 person-years. For solid tumors after MCC, risk was elevated for cutaneous melanoma (SIR, 2.36 [95% CI, 1.85-2.97]; excess risk, 15.27 per 10 000 person-years) and papillary thyroid carcinoma (SIR, 5.26 [95% CI, 3.25-8.04]; excess risk, 6.16 per 10 000 person-years). For hematologic cancers after MCC, risk was increased for non-Hodgkin lymphoma (SIR, 2.62 [95% CI, 2.04-3.32]; excess risk, 15.48 per 10 000 person-years).

Conclusions and Relevance

This cohort study found that patients with MCC had an increased risk of subsequently developing solid and hematologic cancers. This increased risk may be associated with increased surveillance, treatment-related factors, or shared etiologies of the other cancers with MCC. Further studies exploring possible common etiological factors shared between MCC and other primary cancers are warranted.

A review of Merkel cell carcinoma

ABSTRACT

Merkel cell carcinoma (MCC) is a rare and aggressive type of metastatic, nonmelanoma skin cancer derived from Merkel cells in the epidermis. MCC can be induced by sun exposure or via Merkel cell polyomavirus (MCV) gene expression. MCV is found in most patients with MCC and is associated with a lower recurrence rate of MCC. MCC has a wide range of clinical presentations that make diagnosis challenging. Histologic examination is performed using unique markers to differentiate it from other diagnoses. This article reviews the pathogenesis, clinical presentation, histopathology, differential diagnosis, and treatment of MCC.

Review of Merkel cell carcinoma with solitary pancreatic metastases mimicking primary neuroendocrine tumor of the pancreas

OBJECTIVE/BACKGROUND

Merkel cell carcinoma (MCC) but metastases to the pancreas are very rare. There are only a few cases of isolated metastases of MCC to the pancreas. Because of this rarity, it can be wrongly diagnosed as a neuroendocrine tumor of the pancreas(pNET), especially the poorly differentiated neuroendocrine carcinoma (PNEC) subtype, in which the treatment is vastly different than that of MCC with isolated metastases of the pancreas.

METHODS

An electronic search of the PubMed and google scholar databases was performed to obtain the literature on MCC with pancreatic metastases, using the following search terms: Merkel cell carcinoma, pancreas, and metastases. Results are limited to the following available article types: case reports and case series. We identified 45 cases of MCC with pancreatic metastases from the PubMed and Google Scholar database search and examined their potential relevance. Only 22 cases with isolated pancreatic metastases were taken for review including one case that we encountered.

RESULTS

The results from our review of cases of isolated pancreatic metastases of MCC were compared to the characteristics of the poorly differentiated pancreatic neuroendocrine tumor (PNEC). We found the following: (a) MCC with isolated pancreatic metastases occurred at an older age than PNEC and with male gender predominance (b) Most of the metastases occurred within 2 years of initial diagnosis of MCC (c) Resection of pancreatic mass was the first line treatment in case of resectable PNECs whereas resection of metastases was infrequently performed in MCC with pancreatic metastases.

The Evolving Treatment Landscape of Merkel Cell Carcinoma

OPINION STATEMENT

Merkel cell carcinoma (MCC) has a high risk of recurrence and requires unique treatment relative to other skin cancers. The patient population is generally older, with comorbidities. Multidisciplinary and personalized care is therefore paramount, based on patient preferences regarding risks and benefits. Positron emission tomography and computed tomography (PET-CT) is the most sensitive staging modality and reveals clinically occult disease in ~ 16% of patients. Discovery of occult disease spread markedly alters management. Newly diagnosed, localized disease is often managed with sentinel lymph node biopsy (SLNB), local excision, primary wound closure, and post-operative radiation therapy (PORT). In contrast, metastatic disease is usually treated systemically with an immune checkpoint inhibitor (ICI). However, one or more of these approaches may not be indicated. Criteria for such exceptions and alternative approaches will be discussed. Because MCC recurs in 40% of patients and early detection/treatment of advanced disease is advantageous, close surveillance is recommended. Given that over 90% of initial recurrences arise within 3 years, surveillance frequency can be rapidly decreased after this high-risk period. Patient-specific assessment of risk is important because recurrence risk varies widely (15 to > 80%: Merkelcell.org/recur) depending on baseline patient characteristics and time since treatment. Blood-based surveillance tests are now available (Merkel cell polyomavirus (MCPyV) antibodies and circulating tumor DNA (ctDNA)) with excellent sensitivity that can spare patients from contrast dye, radioactivity, and travel to a cancer imaging facility. If recurrent disease is locoregional, management with surgery and/or RT is typically indicated. ICIs are now the first line for systemic/advanced MCC, with objective response rates (ORRs) exceeding 50%. Cytotoxic chemotherapy is sometimes used for debulking disease or in patients who cannot tolerate ICI. ICI-refractory disease is the major problem faced by this field. Fortunately, numerous promising therapies are on the horizon to address this clinical need.

Brief Communication: Lambert-Eaton Myasthenic Paraneoplastic Syndrome Associated With Merkel Cell Carcinoma Successfully Treated by Immune Checkpoint Inhibitors: 2 Cases

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine cutaneous tumor with high metastatic potential. In rare cases, it can be associated with paraneoplastic syndromes (PNS), which result from an antitumor immunity against antigens produced by the tumor itself. Lambert-Eaton Myasthenic Syndrome (LEMS) is a neurological autoimmune PNS characterized by an impairment of the neuromuscular junction, leading to proximal muscle weakness and fatigability. Although the development of immune checkpoint inhibitors (ICI) is a breakthrough in the management of many cancers, onset or worsen of immune diseases has been described. Thereby, in patients with previous neurological PNS like LEMS, the ICI therapy for cancer may aggravate neurological symptoms and lead to irreversible impairment. We report here 2 cases of patients with metastatic MCC associated with a LEMS at the diagnosis. Both successfully received ICI therapies (anti-PDL1 avelumab and anti-PD1 pembrolizumab) without worsening of LEMS and any major immune-related adverse effects. Their neurological condition improved and disappeared concomitantly with the efficacy of immunotherapy, and we did not observe relapse of both MCC and LEMS after treatment discontinuation. Finally, we performed a complete review of the literature, which confirmed that ICI treatment could be discussed for patients with paraneoplastic LEMS, and emphasized the need for multidisciplinary management.

miRNAs driving diagnosis, prognosis and progression in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive form of skin malignancy with a high recurrence commonly within two to three years of initial diagnosis. The incidence of MCC has nearly doubled in the past few decades. Options for diagnosing, assessing, and treating MCC are limited. MicroRNAs (miRNAs) are a class of small, non-coding RNA molecules that play an important role in controlling many different aspects of cell biology. Many miRNAs are aberrantly expressed in distinct types of cancer, with some serving as tumor suppressors and others as oncomiRs. Therefore, the future holds great promise for the utilization of miRNAs in enhancing diagnostic, prognostic, and therapeutic approaches for MCC. Accordingly, the goal of this article is to compile, summarize, and discuss the latest research on miRNAs in MCC, highlighting their potential clinical utility as diagnostic and prognostic biomarkers.

SOX11 Is an Effective Discriminatory Marker, When Used in Conjunction With CK20 and TTF1, for Merkel Cell Carcinoma: Comparative Analysis of SOX11, CK20, PAX5, and TTF1 Expression in Merkel Cell Carcinoma and Pulmonary Small Cell Carcinoma

CONTEXT.—

Distinction between Merkel cell carcinoma (MCC) and pulmonary small cell carcinoma (PSmCC) can be challenging, even with the aid of immunohistochemistry (IHC) analysis of CK20 and TTF1, as these tumors occasionally lack classic immunophenotypes (CK20+/TTF1- in MCC and CK20-/TTF1+ in PSmCC).

OBJECTIVE.—

To evaluate the diagnostic utility of SOX11 and PAX5 IHC for distinguishing MCCs from PSmCCs and compare it with that of CK20 and TTF1 IHC.

DESIGN.—

SOX11, PAX5, CK20, and TTF1 expression (pattern, intensity, and proportion of tumor cells expressing protein) was assessed in 31 primary and 16 metastatic MCCs and 20 primary and 9 metastatic PSmCCs.

RESULTS.—

SOX11 expression was present in all MCCs and was predominantly strong and diffuse. Only 19% of primary and 38% of metastatic MCCs exhibited diffuse PAX5 expression; none exhibited strong immunoreactivity. Strong and diffuse SOX11 expression was seen in less than 25% of primary and metastatic PSmCCs. PAX5 expression was rare in PSmCCs and was mostly weak and focal/patchy. SOX11 expression in at least 26% of tumor cells, with at least moderate intensity, favored the diagnosis of MCC over PSmCC (P < .001). Furthermore, SOX11 expression was more likely than CK20 expression to be strong or diffuse in sentinel lymph node (SLN) metastases of MCC, indicating that SOX11 is superior to CK20 for detecting tumor deposits in SLNs in MCC.

CONCLUSIONS.—

Our findings indicate that SOX11 not only is a powerful marker for distinguishing MCCs from PSmCCs, especially when used in conjunction with CK20 and TTF1, but also has utility for screening SLNs in MCC.

Cytokeratin-20 negative nodal Merkel cell carcinoma with regressed primary: a potential pitfall in interpretation of nodal metastasis

Merkel cell carcinoma (MCC) is a rare, highly aggressive cutaneous neuroendocrine carcinoma that affects sun-damaged skin. Histologically, the tumor consists of round cells with fine chromatin positive for cytokeratin 20 in ~90% of cases. Rare cases of MCC can regress spontaneously and present as nodal metastasis. Nodal MCC of unknown primary can cause a potential pitfall as they can be misinterpreted as other neuroendocrine carcinomas such as small cell carcinoma. We report a case of nodal MCC with an atypical immunohistochemistry pattern presented as bilateral axillary lymphadenopathy in a 90-year-old man with a remote history of a skin lesion that healed spontaneously leaving a scar.

Epidemiology of Merkel cell carcinoma in Tuscany (Italy), 2006-2021

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer that still has a poor prognosis. MCC incidence has increased in recent years worldwide. The aim of our study was to perform an epidemiological retrospective study and to evaluate the impact of MCC clinical and pathological features on overall survival (OS) in a specific geographical area. We retrospectively collected 94 pathology reports from 2006 to 2021 that were present in the pathology archives of the University Hospital of Pisa and of the Hospital of Livorno. Laterality was different according to the site, and almost half of the lesions were T1 and nearly half of the patients had a clinical stage III. We reported a dramatic increase in MCC diagnoses in the last 5 years compared with the previous years, with a crude incidence rate of 1,15/100000 inhabitants, almost doubling the last reported data in Italy. Surgical margins status and ulceration were not related to OS. We have noticed some patients with a rapidly progressing disease and others showing a slow disease progression which should prompt the investigation of specific biomarkers or other features that could elucidate this striking difference in progression-free survival and could potentially identify different subtypes of MCC. Considering the generally low incidence of MCC worldwide, larger cohorts would be necessary to validate our data and to obtain a better prognostic stratification.

A rare involvement in skin cancer: Merkel cell carcinoma with bone marrow infiltration in a kidney transplant recipient

A 60-year-old man presented with a painless, rapidly growing, haemorrhagic pink nodule on the posterior of his thigh that had developed 1 month previously. He had a diagnosis of IgA nephropathy and had received a renal allograft 7 years before. An excisional biopsy was performed and the diagnosis of Merkel cell carcinoma (MCC) was made. No distant metastases was detected. 10 months after first presentation, due to the development of acute pancytopenia and concomitant FDG PET/CT findings compatible with disease progression, bone marrow biopsy was performed which revealed metastasis of MCC. Dermatologists and oncologists should be aware that MCC could potentially involve the bone marrow in organ transplant recipients. In the follow-up period, a complete blood count should be carried out; FDG PET/CT can be obtained to follow up the metabolic status of the disease and bone marrow biopsy should be performed if necessary.

S2k Guideline - Merkel cell carcinoma (MCC, neuroendocrine carcinoma of the skin) - Update 2022

Merkel cell carcinoma (MCC, ICD-O M8247/3) is a rare, malignant, primary skin tumor with epithelial and neuroendocrine differentiation. The tumor cells share many morphologic, immunohistochemical, and ultrastructural features with cutaneous Merkel cells. Nevertheless, the cell of origin of MCC is unclear. MCC appears clinically as a reddish to purple spherical tumor with a smooth, shiny surface and a soft to turgid, elastic consistency, usually showing rapid growth. Spontaneous and often complete regressions of the tumor are observed. These likely immunologically-mediated regressions explain the cases in which only lymph node or distant metastases are found at the time of initial diagnosis and why the tumor responds very well to immunomodulatory therapies even at advanced stages. Due to its aggressiveness, the usually given indication for sentinel lymph node biopsy, the indication of adjuvant therapies to be evaluated, as well as the complexity of the necessary diagnostics, clinical management should already be determined by an interdisciplinary tumor board at the time of initial diagnosis.

A Regional Survey on Merkel Cell Carcinoma: A Plea for Uniform Patient Journey Modeling and Diagnostic-Therapeutic Pathway

Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous neuroendocrine cancer that usually affects the elderly and immunosuppressed in sun-exposed areas. Due to its rarity, it is frequently unrecognized, and its management is not standardized across medical centers, despite the more recent availability of immunotherapy, with avelumab as first-line treatment improving the prognosis even in advanced stages of disease. We conducted a purpose-designed survey of a selected sample of physicians working in the Lazio region, in Italy, to assess their awareness and knowledge of MCC as well as their perspective on assisted diagnostic and therapeutic pathways. The Lazio region, and in particular Rome, is one of the most important academic and non- academic center in Italy dedicated to the diagnosis and treatment of skin cancer. A total of 368 doctors (including 100 general practitioners, 72 oncologists, 87 dermatologists, 59 surgeons, and 50 anatomopathologists) agreed to be part of this survey. Surgeons, oncologists, and dermatologists thought themselves significantly more updated on MCC than primary care physicians, but more than half of the interviewees are interested in CCM training courses and training with clearer and more standardized care pathways. Significant differences have been reported from survey participants in terms of multidisciplinary team set up for MCC management. The identification of specialized centers and the improvement of communication pathways among different specialties, as well as between patients and physicians, could be very beneficial in improving patients' journey modeling and starting a uniform diagnostic and therapeutic pathway for MCC patients in the new era of immunotherapies.

A Retrospective Study of Ipilimumab Plus Nivolumab in Anti-PD-L1/PD-1 Refractory Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a very rare but highly aggressive cutaneous neuroendocrine carcinoma and is associated with chronic exposure to ultraviolet light and the Merkel cell polyoma virus. The incidence rate of MCC is increasing and MCC is associated with high rates of recurrence and mortality. Immune checkpoint inhibitors (ICIs) offer durable responses and significant clinical benefit with 2 agents-avelumab (anti-PD-L1) and pembrolizumab (anti-PD-1)-currently approved by the U.S. Food and Drug Administration for the treatment of advanced MCC. Despite the advances in systemic therapy options for MCC, ~50% of patients with advanced MCC treated with ICI progress on therapy. There is a paucity of studies assessing second-line systemic therapy following primary/acquired resistance to ICIs. Current management in this setting remains a clinical challenge especially in trial ineligible patients. We evaluated objective response to ipilimumab plus nivolumab in metastatic MCC refractory to anti-PD-(L)1 therapy. Thirty-one percent of patients experienced a grade III or grade IV immune-related adverse event (irAE) due to ipilimumab plus nivolumab. No patients (0/13) achieved a complete or partial response via RECISTv1.1/irRECIST. Twenty-three percent (3/13) of patients achieved stable disease as the best overall response but progressed shortly thereafter. The median progression-free survival was 1.3 months (90% CI 1.1-1.5) from the initiation of ipi-nivo. The median overall survival was 4.7 months (95% CI 3-17). This study suggests limited, if any, clinical benefit of ipi-nivo in patients with advanced anti-PD-L1/anti-PD-1 refractory MCC.

Merkel Cell Carcinoma In Situ: No More Serendipity?

ABSTRACT

A 50-year-old man, with a history of extensive sun exposure and multiple previous non-melanoma skin cancers, presented with an asymptomatic 8-× 10-millimeter scaly, skin-colored papule on his right shoulder. Subsequent biopsy and excision revealed epidermal hyperplasia containing large atypical basaloid cells with pagetoid spread. Immunoperoxidase staining for cytokeratin-20 demonstrated a focal perinuclear dot-like pattern, and after excluding other in situ entities, a diagnosis of Merkel cell carcinoma In Situ (MCCIS) was rendered. MCCIS is a very rare entity. Although approximately 18% of Merkel cell carcinomas have epidermal involvement, currently only 17 cases of MCCIS have been reported, of which only 7 had no associated neoplasm. Previously, MCCIS was considered a serendipitous or incidental finding, as most cases co-existed with squamous cell carcinoma in situ. This case is unique in that it was not associated with a squamous lesion, and in addition, the pagetoid spread was unusual and has only occasionally been described. As such, MCCIS should be added to list of in situ epidermal lesions with pagetoid spread.

Extrafacial Merkel Cell Carcinoma Presenting as a Cyst

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine skin tumor that presents as an erythematous or violaceous nodule in elderly white males with an extensive history of sun exposure. Herein, we report two cases of extrafacial MCC. On exam, lesions presented as a cystic nodule and a firm plaque. We summarize tools from literature review that may aid in earlier diagnosis of MCC as well as implications of primary tumor location in prognosis. In addition, we provide an algorithm for diagnostic workup. MCC is an aggressive malignancy with a poor prognosis and a high risk of local recurrence and nodal metastasis. It is imperative to include MCC in differential diagnosis of cyst/nodule in order to facilitate early detection. J Drugs Dermatol. 2022;21(3):304-308. doi:10.36849/JDD.6248.

A Challenging Nodular Lesion of the Ear

Skin nodular lesion are really frequent, but rapidly growing ones needs to be quickly removed since they can hide really aggressive skin tumor. Among malignant lesion Merkel cell carcinoma arise. It is a rare neuroendocrine skin tumor highly aggressive, not easy to diagnose at first stage, since at first diagnosis it is already widespreading all over the body. In order to renew interest in this letal skin tumori is mandatory to remind high risk population which include elderly people, white skin, chronically exposed to UV immunocompromised. Our unhappy case was described to increase awareness on this kind of skin tumor, since new drug appeared in the market can give an hope to these patients.

Immunotherapy for Nonmelanoma skin cancer: Facts and Hopes

Non-melanoma skin cancer (NMSC) is the most frequently diagnosed malignancy in humans, representing a broad range of cutaneous tumors. Keratinocyte carcinomas, including basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (CSCC), are the most common NMSCs. The incidence of BCC and CSCC are steadily increasing due to a progressively aging population, chronic exposure to ultraviolet radiation, and increased awareness with earlier diagnosis. Rarer NMSCs such as Merkel cell carcinoma (MCC) and cutaneous adnexal carcinomas (CACs) are also on the rise. Although the majority of NMSC tumors are localized at diagnosis and managed effectively with curative surgery and radiation, in rare cases with nodal and distant metastases, systemic therapy is often required. As our understanding of the immunologic characteristics of NMSCs has improved, effective treatment options have expanded with the development of immunotherapy. The U.S. Food and Drug Administration (FDA) recently approved several immune checkpoint inhibitors for the treatment of locally advanced and metastatic MCC, CSCC, and BCC. We review the emerging role of immunotherapy as the standard of care for several advanced NMSCs not amenable to surgery and/or radiation and underscore the need for considering clinical trials of novel strategies in patients when immunotherapy does not provide durable benefit. Finally, we explore the potential of neoadjuvant and adjuvant immunotherapy.

Advances in Immunology: A Cornerstone in Diagnosis and Therapy of Merkel Cell Carcinoma

Merkel cell cancer (MCC) is a rare cutaneous malignancy arising from neuroendocrine cells. This rare but lethal malignancy (mortality greater than 30%) has also tripled in incidence over the last two decades. The role of immunodeficiency in pathogenesis of this rare malignancy is well established, with elucidation of viral pathogenesis by Merkel cell polyoma virus (MCPyV), a novel polyoma virus, in a majority of patients. Viral neoantigens while playing an important role in oncogenesis can also aid in early immunologic detection of recurrent disease. Viral neoantigens can also be targets for immunotherapy. Immune checkpoint inhibitors (ICI) have established role in frontline therapy in addition to recurrence of metastatic MCC. ICI therapy is being explored in adjuvant and neoadjuvant settings as well. We would like to illustrate curative potential of early diagnosis of recurrence and prompt use of ICI in treatment of oligometastatic disease in our case presentation.

Merkel Cell Carcinoma: A Bibliometric Analysis of the Top 100 Cited Publications

BACKGROUND

Bibliometric studies provide a quantitative statistical analysis of the published literature within a field of interest and allow for easy identification of the major contributing authors, funding sources, and publication trends within the field. To date, no bibliometric studies have been performed pertaining to Merkel cell carcinoma (MCC).

OBJECTIVE

To identify the 100 most frequently cited articles in MCC through a bibliometric analysis of the literature.

METHODS

Web of science was queried to determine the 100 most frequently cited MCC publications published between the years 1970 and 2019. Articles were listed by title, authors and their affiliated institutions, journal title and type, year of publication, country of origin, funding sources, and citation frequency.

RESULTS

Among the 100 most frequently cited MCC publications, articles were cited between 67 and 589 times with a mean of 136.3 times. Articles were cited between 2.0 and 98.2 times per year since publication with a mean of 11.3 times per year. 67% of the articles were published in oncology journals; 33% and 10% of the articles in dermatology and surgery journals, respectively. The most represented journal was Cancer (12%). Paul Nghiem was the most frequently identified author (18%). 36% of the top 100 articles were published out of the University of Washington. The most frequent funding agency was the National Institutes of Health (77%).

CONCLUSION

Through this bibliometric analysis, researchers can easily identify key publications pertaining to MCC, which may in turn enhance their approach to understanding and practicing evidence-based medicine regarding MCC.

Scientific and clinical developments in Merkel cell carcinoma: A polyomavirus-driven, often-lethal skin cancer

Merkel cell carcinoma (MCC) is a primary neuroendocrine skin cancer that recurs in ~40% of cases. Merkel cell polyomavirus (MCPyV) and ultraviolet (UV)-induced mutations are two major causative factors of MCC. Virus-positive MCCs express polyomavirus oncoproteins that are highly immunogenic yet are required for ongoing tumor growth. Virus-negative MCCs have a high burden of UV-DNA mutations that encode tumor-specific UV-neoantigens. Thus, both UV- and virus-induced MCCs are highly immunogenic, enabling diverse T-cell targeted therapies. Optimal MCC management is challenging given its rarity, aggressive nature, rapidly evolving care guidelines, and fundamental differences in management compared to other skin cancers. MCC is often managed aggressively with extensive surgery, radiotherapy or systemic therapy, frequently leading to toxicities that might have been avoidable while still achieving optimal disease control. Thus, multi-disciplinary care is crucial for providing patients with the best possible outcomes. The outlook for many patients with advanced MCC has progressed remarkably over the past decade due to PD-1 pathway blocking agents that provide durable benefit for a substantial subset of MCC patients. The management of early-stage MCC has also improved due to better approaches to integrate surgery and radiotherapy. Prognostic accuracy and ongoing surveillance have advanced due to stage-specific recurrence data and sophisticated "liquid biopsies" that allow early detection of disease recurrence. Here we summarize both recent striking progress and pressing challenges such as PD-(L)1-refractory MCC, and management of MCC patients with immune dysfunction. We also highlight diverse resources to allow providers to take advantage of recent progress in this fast-moving field.

Updates on the diagnosis, current and future therapeutic options in Merkel-cell carcinoma

Merkel-cell carcinoma (MCC) is a rare and extremely aggressive nonmelanocytic cutaneous neuroendocrine carcinoma. Historically, it has been associated with limited therapy options and poor prognosis. While its incidence has been rising over the last two decades, recent discoveries and a better understanding of its pathogenesis, viral association and immunologic features have allowed for the emergence of new therapies. Surgical excision with or without radiotherapy remains the first-line therapy for primary lesions without evidence of metastatic disease. The majority of MCC cases are regrettably diagnosed at advanced stages and oftentimes require systemic therapy. There have been several significant advances in the treatment of MCC in the last decade. Among these have been the development of immune checkpoint inhibitors targeting the programmed death protein-1 (PD-1)/programmed death ligand-1 (PDL-1). Despite recent success of immunotherapy, nearly 50% of patients diagnosed with MCC still succumb to the disease. Fortunately, there has been a number of new targeted therapies that hold great promise. Among them are phosphatidylinositide-3kinase (Pl3K) inhibitors, adoptive T-cell immunotherapy, activated NK-92 cells infusions and therapeutic vaccines. Additional emerging therapeutic targets include cellular ubiquitin-specific processing protease 7 (Usp7) that restricts viral replication and IFN genes (STING), activation of which promotes an antitumor inflammatory response.

Characterizing DNA methylation signatures and their potential functional roles in Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer with limited treatment possibilities. Merkel cell tumors display with neuroendocrine features and Merkel cell polyomavirus (MCPyV) infection in the majority (80%) of patients. Although loss of histone H3 lysine 27 trimethylation (H3K27me3) has been shown during MCC tumorigenesis, epigenetic dysregulation has largely been overlooked.

METHODS

We conducted global DNA methylation profiling of clinically annotated MCC primary tumors, metastatic skin tumors, metastatic lymph node tumors, paired normal tissues, and two human MCC cell lines using the Illumina Infinium EPIC DNA methylation BeadArray platform.

RESULTS

Significant differential DNA methylation patterns across the genome are revealed between the four tissue types, as well as based on MCPyV status. Furthermore, 964 genes directly regulated by promoter or gene body DNA methylation were identified with high enrichment in neuro-related pathways. Finally, our findings suggest that loss of H3K27me3 occupancy in MCC is attributed to KDM6B and EZHIP overexpression as a consequence of promoter DNA hypomethylation.

CONCLUSIONS

We have demonstrated specific DNA methylation patterns for primary MCC tumors, metastatic MCCs, and adjacent-normal tissues. We have also identified DNA methylation markers that not only show potential diagnostic or prognostic utility in MCC management, but also correlate with MCC tumorigenesis, MCPyV expression, neuroendocrine features, and H3K27me3 status. The identification of DNA methylation alterations in MCC supports the need for further studies to understand the clinical implications of epigenetic dysregulation and potential therapeutic targets in MCC.

[Merkel cell carcinoma]

Merkel cell carcinoma is a neuroendocrine skin carcinoma caused by the Merkel cell virus and ultraviolet radiation. Approximately 25 Danish patients are diagnosed each year. Merkel cell carcinoma is often located on the sun-exposed areas of the skin and definitive diagnosis is made by the pathologist. Patients are treated at the department of plastic surgery and oncology with treatment modalities including surgery, radiotherapy, immunotherapy and chemotherapy as summarised in this review.

Chronic lymphocytic leukemia and second primary nonlymphoid malignancies: cytopathologic study of 17 cases

INTRODUCTION

Second primary nonlymphoid malignancies (SPNLM) have long been recognized as a complication of chronic lymphocytic leukemia (CLL).

MATERIALS AND METHODS

A search was made of our cytopathology database for cases of CLL that also contained a SPNLM.

RESULTS

Seventeen cases from 13 known CLL patients [M:F = 2.3:1; age range: 47-77 years, x = 67 years] met criteria for this study. SPNLMs consisted of different forms of metastatic carcinoma (10 patients) and malignant melanoma (3). Of 16 FNA biopsies and 1 pleural fluid, 82% had ancillary testing; 35% had the specimen subdivided for both flow cytometry (FCM) and immunohistochemistry (IHC). Lymph node was the most common site for FNA biopsy (12), followed by face (2), and soft tissue (2). Squamous cell carcinoma was the most common SPNLM (6), followed by melanoma (3), and there were single cases of adenocarcinoma, large cell neuroendocrine carcinoma, Merkel cell carcinoma, and papillary thyroid carcinoma. A correct specific cytologic diagnosis was made in 15 (88%) cases.

CONCLUSIONS

Cytopathology is highly proficient in recognizing SPNLM in CLL patients. Utilization of cytologic material for FCM and IHC is feasible, and extremely helpful in achieving diagnostic accuracy.