Merkel cell carcinoma: pathologic findings and prognostic factors

Metastatic merkel cell carcinoma to the thyroid gland: Case report and review of the literature

BACKGROUND

Merkel cell carcinoma (MCC) is an aggressive and rare neuroendocrine tumor, accounting for less than 1% of skin cancers. Metastasis primarily manifests in the cervical lymph nodes but rarely affect the thyroid.

METHODS

We report a case of primary head and neck cutaneous MCC with metastasis to the thyroid gland. A review of the literature of MCC with thyroid metastasis was conducted.

RESULTS

We identified five cases of MCC with thyroid metastasis. Primary sites included the distal upper and lower extremities, axilla, buttock, and groin. Treatment courses varied including thyroidectomy, immunotherapy, and expectant palliative measures. Time from initial diagnosis to thyroid metastasis ranged from four months to four years. Tissue diagnosis was achieved in 5 of 6 cases.

CONCLUSIONS

MCC with thyroid metastasis is rare and likely represents aggressive disease. Despite advances in treatment and surveillance, outcomes for MCC remain poor. Ongoing research may establish predictors for treatment response.

Merkel cell carcinoma: an update

Merkel cell carcinoma (MCC) is an uncommon primary cutaneous neuroendocrine carcinoma associated with an adverse prognosis. In recent years, our understanding of MCC biology has markedly progressed. Since the discovery of the Merkel cell polyomavirus, it has become clear that MCC represents an ontogenetically dichotomous group of neoplasms with overlapping histopathology. Specifically, most MCCs arise secondary to viral oncogenesis, while a smaller subset is the direct result of UV-associated mutations. The distinction of these groups bears relevance in their immunohistochemical and molecular characterization, as well as in disease prognosis. Further recent developments relate to the landmark utilization of immunotherapeutics in MCC, providing optimistic options for the management of this aggressive disease. In this review, we discuss both fundamental and emerging concepts in MCC, with a particular focus on topics of practical relevance to the surgical or dermatopathologist.

YAP1 and WWTR1 expression inversely correlates with neuroendocrine markers in Merkel cell carcinoma

BackgroundMerkel cell carcinoma (MCC) is an aggressive neuroendocrine (NE) skin cancer caused by severe UV-induced mutations or expression of Merkel cell polyomavirus (MCPyV) large and small T antigens (LT and ST). Despite deep genetic differences between MCPyV-positive and -negative subtypes, current clinical diagnostic markers are indistinguishable, and the expression profile of MCC tumors is, to our knowledge, unexplored.MethodsHere, we leveraged bulk and single-cell RNA-Seq of patient-derived tumor biopsies and cell lines to explore the underlying transcriptional environment of MCC.ResultsStrikingly, MCC samples could be separated into transcriptional subtypes that were independent of MCPyV status. Instead, we observed an inverse correlation between a NE gene signature and the Hippo pathway transcription factors Yes1-associated transcriptional regulator (YAP1) and WW domain-containing transcriptional regulator 1 (WWTR1). This inverse correlation was broadly present at the transcript and protein levels in the tumor biopsies as well as in established and patient-derived cell lines. Mechanistically, expression of YAP1 or WWTR1 in a MCPyV-positive MCC cell line induced cell-cycle arrest at least in part through TEA domain-dependent (TEAD-dependent) transcriptional repression of MCPyV LT.ConclusionThese findings identify what we believe to be a previously unrecognized heterogeneity in NE gene expression within MCC and support a model of YAP1/WWTR1 silencing as essential for the development of MCPyV-positive MCC.FundingUS Public Health Service grants R35CA232128, P01CA203655, and P30CA06516.

Unique presentation of Merkel cell tumour affecting the hand

Merkel cell carcinoma (MCC) is a rare and highly aggressive skin cancer which most commonly occurs on the head and neck. A limited number of cases of MCC of the hand have been reported in the English literature. We describe a case of MCC of the hand in a man in his late 60s. The lesion presented on the dorsum of the left fifth digit, with metastasis to the left axillary lymph nodes. The primary lesion grew rapidly over a span of 3 months. The patient was treated with two courses of neoadjuvant nivolumab, amputation of the digit and left axillary lymph node resection followed by radiotherapy to the left hand and left axilla. He continues to follow-up for radiotherapy treatment 3 months postoperatively.

Merkel Cell Carcinoma: An updated review of pathogenesis, diagnosis, and treatment options

Merkel cell carcinoma is a rare neuroendocrine carcinoma that typically appears in sun-exposed areas of the elderly. It has a poor prognosis and with its incidence projected to increase, it is vital for dermatologists to remain up to date with recent updates in this malignancy's pathogenesis and treatment. In the past few decades Merkel cell carcinoma's pathogenesis, more specifically its relation to the Merkel cell polyomavirus, has sparked further interest in the study of this carcinoma. Most cases are attributed to malignant transformation secondary to the Merkel cell polyomavirus, with a minority derived from DNA damage resulting from ultraviolet radiation. Investigators have also determined that there are immunologic influences in the development and prognosis of Merkel cell carcinoma, as individuals with HIV, solid organ transplants, and lymphoproliferative malignancies are at a greater risk of developing this carcinoma. Also, this immunologic link carries treatment value, as immunologic therapies are currently being investigated. This article provides a comprehensive review of the epidemiology and pathogenesis of Merkel cell carcinoma as well as the current treatments available and clinical trials underway. We also touch upon the updated National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology in respect to its diagnosis and recommended treatment modalities.

Evidence of proliferative activity in human Merkel cells: implications in the histogenesis of Merkel cell carcinoma

The cellular origin of Merkel cell carcinoma (MCC) is controversial. We previously hypothesized that MCC originates from hair follicle stem cells or Merkel cell (MC) progenitors residing within the hair follicle bulge. Examination of three cases of combined MCC led to the unexpected discovery that numerous keratin 20 (CK20)-positive MCs within the squamous cell carcinoma (SCC) component of combined MCC appeared morphologically normal with dendritic and oval shapes. Moreover, one extremely rare case of combined SCC and MCC showed both intra-epidermal and dermal MCCs. These three cases represent the first documentation of MC hyperplasia in MCC, besides various benign follicular neoplasms associated with MC hyperplasia. Therefore, to elucidate the proliferating potential of MCs and their histogenetic relationship with MCCs, we further investigated these cases based on pathological observations. We identified numerous cells co-expressing CK20 and the proliferation marker Ki-67, identical to the morphological and immunohistochemical features of normal MCs. This finding indicated that MCs can no longer be considered as pure post-mitotic cells. Instead, they have proliferative potential under specific conditions in the diseased or wounded skin, or adjacent to various skin tumors, including MCC. Intimate co-existence of two malignant cell components composed of intradermal and intra-epidermal MCCs, with the proliferation of normal-appearing MCs in the same lesion, lends support to the hypothesis that MCs and MCC cells are derived from MC progenitors residing within the hair follicle bulge. Specifically, MCCs are derived from transformed MC progenitors with potential for dual-directional differentiation towards neuroendocrine and epithelial lineages.

Insulinoma-associated 1: A novel nuclear marker in Merkel cell carcinoma (cutaneous neuroendocrine carcinoma)

Merkel cell carcinoma (MCC) is a rare, clinically aggressive, cutaneous neuroendocrine (NE) neoplasm. As a tumor with small, round, blue cells, the histologic differential diagnosis for MCC can include melanoma, metastatic small cell carcinoma (SCC), nodular hematopoietic tumors, basal cell carcinoma (BCC), atypical variants of squamous carcinoma and the uncommon occurrence of primary cutaneous Ewing sarcoma. In cases with atypical histology or without the classic immunophenotype, the diagnosis can be challenging. Ultimately, immunohistochemistry (IHC) is essential to the definitive diagnosis of MCC and in difficult cases, the diagnosis may hinge entirely on the immunophenotype of the tumor cells. Insulinoma-associated 1 (INSM1) is a transcription factor expressed in tissues undergoing terminal NE differentiation. As a nuclear protein tied to both differentiation and the cell cycle, INSM1 may offer additional utility in comparison to traditional, cytoplasmic markers of NE differentiation.

Intraepidermal Merkel cell carcinoma: A case series of a rare entity with clinical follow up

BACKGROUND

Merkel cell carcinoma (MCC) is a rare but aggressive cutaneous carcinoma. MCC typically involves dermis and although epidermotropism has been reported, MCC strictly intraepidermal or in situ (MCCIS) is exceedingly rare. Most of the cases of MCCIS described so far have other associated lesions, such as squamous or basal cell carcinoma, actinic keratosis and so on. Herein, we describe 3 patients with MCC strictly in situ, without a dermal component.

METHODS

Our patients were elderly. 2 of the lesions involved the head and neck area and 1 was on a finger. All tumors were strictly intraepidermal in the diagnostic biopsies, and had histomorphologic features and an immunohistochemical profile supporting the diagnosis of MCC. Excisional biopsies were performed in 2 cases and failed to reveal dermal involvement by MCC or other associated malignancies.

RESULTS AND CONCLUSION

Our findings raise the awareness that MCC strictly in situ does exist and it should be included in the differential diagnosis of Paget's or extramammary Paget's disease, pagetoid squamous cell carcinoma, melanoma and other neoplasms that typically show histologically pagetoid extension of neoplastic cells. Considering the limited number of cases reported to date, the diagnosis of isolated MCCIS should not warrant a change in management from the typical MCC.

Shared Oncogenic Pathways Implicated in Both Virus-Positive and UV-Induced Merkel Cell Carcinomas

Merkel cell carcinoma (MCC) is a highly malignant neuroendocrine tumor of the skin whose molecular pathogenesis is not completely understood, despite the role that Merkel cell polyomavirus can play in 55-90% of cases. To study potential mechanisms driving this disease in clinically characterized cases, we searched for somatic mutations using whole-exome sequencing, and extrapolated our findings to study functional biomarkers reporting on the activity of the mutated pathways. Confirming previous results, Merkel cell polyomavirus-negative tumors had higher mutational loads with UV signatures and more frequent mutations in TP53 and RB compared with their Merkel cell polyomavirus-positive counterparts. Despite important genetic differences, the two Merkel cell carcinoma etiologies both exhibited nuclear accumulation of oncogenic transcription factors such as NFAT or nuclear factor of activated T cells (NFAT), P-CREB, and P-STAT3, indicating commonly deregulated pathogenic mechanisms with the potential to serve as targets for therapy. A multivariable analysis identified phosphorylated CRE-binding protein as an independent survival factor with respect to clinical variables and Merkel cell polyomavirus status in our cohort of Merkel cell carcinoma patients.

Immunoglobulin expressions are only associated with MCPyV-positive Merkel cell carcinomas but not with MCPyV-negative ones: comparison of prognosis

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer, often associated with Merkel cell polyomavirus (MCPyV). Recently, immunoglobulin (Ig) expression was reported in MCC, thereby suggesting that B cells might be their cellular ancestors. We tested 30 MCCs (20 MCPyV-positive and 10 MCPyV-negative) using immunohistochemistry for the expressions of IgG, IgA, IgM, Igκ, Igλ, terminal desoxynucleotidyl transferase, paired box gene 5 (PAX5), octamer transcription factor-2 (Oct-2), and sex-determining region Y-box 11 (SOX11). We performed in situ hybridization for Igκ-mRNA or Igλ-mRNA and Ig heavy chain (IgH) gene rearrangement (IgH-R) analyses. The expressions of PAX5, TdT, Oct-2, and SOX11 were not significantly different between MCPyV-positive and MCPyV-negative MCCs. At least 1 of IgG, IgA, IgM, or Igκ was expressed in MCPyV-positive (14/20, 70%) and none in MCPyV-negative MCCs (P=0.0003). There was a higher tendency for Igκ-mRNA expression (7/19, using in situ hybridization) and IgH-R (10/20, using polymerase chain reaction) in MCPyV-positive than in MCPyV-negative MCCs (0/10 and 2/10, respectively), thus suggesting a different Ig production pattern and pathogenesis between the 2 types of MCC. Ig expression or IgH-R in MCPyV-positive MCCs might be associated with MCPyV gene integration or expression in cancer cells but do not necessarily suggest a B-cell origin for MCCs. IgH expression or IgH-R nonsignificantly correlated with improved prognosis. However, these might be important factors that influence the survival of neoplastic cells and might allow the development of novel therapies for patients with MCPyV-positive MCCs.

Merkel cell carcinoma: a review and update on aetiopathogenesis, diagnosis and treatment approaches

Merkel cell carcinoma (MCC) or primary cutaneous neuroendocrine carcinoma is a relatively uncommon form of skin cancer. It is an aggressive neoplasm with high tendency for local recurrence and lymph node and distant metastasis, whose incidence has been rising in the last 2 decades.A novel polyomavirus (MCPyV) has been found in a significant proportion of MCCs, and this finding significantly contributed to the understanding of its pathogenesis.It is fairly consensual at the current state of know-ledge that appropriate staging, including sentinel lymph node biopsy, is very important in order to plan adequate treatment. Treatment includes aggressive surgery of the primary tumour and lymph node basin, commonly combined with adjuvant radiotherapy. Chemotherapy is usually reserved for distant metastasis.In the present article, the authors review the current knowledge about MCC with special emphasis on the new pathogenetic findings and current recommendations regarding management.

Early B-cell differentiation in Merkel cell carcinomas: clues to cellular ancestry

Merkel cell carcinoma (MCC) is a highly malignant neuroendocrine nonmelanoma skin cancer, which is associated with the Merkel cell polyoma virus (MCPyV). Recently, expression of the terminal deoxynucleotidyl transferase (TdT) and the paired box gene 5 (PAX 5) has been consistently reported in the majority of MCCs. We tested 21 MCCs for the expression of MCPyV, TdT, PAX5, IgG, IgM, IgA, kappa, and lambda by immunohistochemistry and assessed IgH and Igk rearrangement in all 21 MCCs. All of the MCCs revealed specific expression of PAX5 and 72.8% of the MCCs expressed TdT. In addition, most of the MCCs revealed specific expression of one or more Ig subclasses and kappa or lambda. One MCC did reveal monoclonal IgH and Igk rearrangement next to two other MCCs showing Igk rearrangement. As coexpression of TdT and PAX5 under physiologic circumstances is restricted to pro/pre- and pre-B cells we propose, on the basis of our results, that the cell of origin of MCCs is a pro/pre- or pre-B cell rather than the postmitotic Merkel cells. MCPyV infection and transformation of pro-/pre-B cells are likely to induce the expression of simple cytokeratins as has been shown for SV40 in other nonepithelial cells. This model of cellular ancestry of MCCs might impact therapy and possibly helps to understand why approximately 20% of MCCs are MCPyV-negative.

[A probable etiological role of Merkel cell polyomavirus in the development of Merkel cell carcinoma]

Approximately 20% of the tumours in humans are associated with contagious viral agents. Merkel cell carcinoma is a rare and highly aggressive tumour which may originate from the epidermal stratum basale, although the origin is still controversial. This tumour is most commonly found in elderly and immunocompromised patients in sun exposed areas, especially in the head and neck regions. Merkel cell carcinoma often causes a diagnostic challenge with a dramatically increasing incidence. In 2008, a DNA tumour virus, a polyomavirus (Merkel cell polyomavirus) was detected in Merkel cell carcinomas, and this finding helped to understand the etiological background of the disease. The infectious - probably viral - etiology resulted in a paradigm shift in pathogenesis and, hopefully, in therapy as well. This review summarizes the current knowledge related to Merkel cell carcinoma and the first oncogenic human polyomavirus, the Merkel cell polyomavirus, to promote the clinical adaptation of the information.

Which are the cells of origin in merkel cell carcinoma?

Merkel cell carcinoma (MCC), a highly aggressive skin tumour with increasing incidence, is associated with the newly discovered Merkel cell polyomavirus (MCPyV). Studies on MCC and MCPyV as well as other risk factors have significantly increased our knowledge of MCC pathogenesis, but the cells of origin, which could be important targets in future therapies, are still unknown. Merkel cells (MCs), the neuroendocrine cells of the skin, were believed to be at the origin of MCC due to their phenotypic similarities. However, for several reasons, for example, heterogeneous differentiation of MCCs and postmitotic character of MCs, it is not very likely that MCC develops from differentiated MCs. Skin stem cells, probably from the epidermal lineage, are more likely to be cells of origin in MCC. Future studies will have to address these questions more directly in order to identify the physiological cells which are transformed to MCC cells.

Uncommon cutaneous neoplasms of the head and neck

This article concentrates on the less-common cutaneous malignancies such as merkel cell, atypical fibroxanthoma, malignant fibrous histiocytoma, dermatofibrosarcoma protuberans, microcystic adnexal carcinoma, and sebaceous carcinoma. The clinical and histopathologic descriptions of each, most current and emerging etiologies, diagnosis, staging, treatment, and prognosis are discussed.

Dermatology clinics: what's new in dermatopathology: news in nonmelanocytic neoplasia

This article reviews the recent dermatopathology literature involving nonmelanocytic neoplasia, with a focus on important work done over the last 5 years. The discussion includes advances in the understanding of Merkel cell carcinoma pathogenesis and prognosis; changes in the seventh edition of the American Joint Committee of Cancer staging manual in reference to staging of squamous cell carcinoma and Merkel cell carcinoma; newly described or rare histopathologic patterns and entities including squamoid eccrine ductal carcinoma, rippled-pattern adnexal neoplasms, onychomatricoma, spindle cell predominant trichodiscoma/neurofollicular hamartoma, and myoepithelioma; and microsatellite instability in sebaceous neoplasms of Muir-Torre syndrome and other tumors.

Merkel cell carcinoma in a patient with noninvasive vulvar Paget's disease

We present the first case of inguinal Merkel cell carcinoma of unknown primary origin in a patient with vulvar Paget's disease. Correlation with immune suppression of both entities warrants further investigation. Additionally, this case highlights the value of ultrasound scanning in the detection of inguinal metastasis.

Histological, immunohistological, and clinical features of merkel cell carcinoma in correlation to merkel cell polyomavirus status

Merkel cell carcinoma is a rare, but highly malignant tumor of the skin with high rates of metastasis and poor survival. Its incidence rate rises and is currently about 0.6/100000/year. Clinical differential diagnoses include basal cell carcinoma, cyst, amelanotic melanoma, lymphoma and atypical fibroxanthoma. In this review article clinical, histopathological and immunhistochemical features of Merkel cell carcinoma are reported. In addition, the role of Merkel cell polyomavirus is discussed.

Merkel cell carcinoma of unknown primary origin

BACKGROUND

Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin. MCC from an unknown primary origin (MCCUP) can present a diagnostic and therapeutic challenge. We describe our single-institution experience with the diagnosis and management of MCCUP presenting as metastases to lymph nodes.

METHODS

After institutional review board approval, our institutional database spanning the years 1998-2010 was queried for patients with MCCUP. Clinicopathologic variables and outcomes were assessed.

RESULTS

From a database of 321 patients with MCC, 38 (12%) were identified as having nodal MCCUP. Median age was 67 years, and 79% were men. Nodal basins involved at presentation were cervical (58%), axillary/epitrochlear (21%), or inguinal/iliac (21%). CK20 staining was positive in 93% of tumors tested, and all were negative for thyroid transcription factor-1. Twenty-nine patients (76%) underwent complete regional lymph node dissection (LND): 3 had LND alone, ten had LND and adjuvant radiotherapy, and 16 underwent LND followed by chemoradiotherapy. Definitive chemoradiotherapy without surgery was provided to six patients (16%), while radiotherapy alone was provided to three (8%). Recurrence was observed in 34% of patients. Median recurrence-free survival was 35 months. Ten patients (26%) died, five of disease and five of other causes. The median overall survival was 104 months.

CONCLUSIONS

Nodal MCCUP is a rare disease affecting primarily elderly white men. Recurrence is observed in approximately one-third of patients, with a 104 month median overall survival after a multimodal treatment approach consisting of surgery along with adjuvant chemotherapy and radiotherapy in the majority of patients.

Advances in Merkel cell carcinoma pathogenesis and management: a recently discovered virus, a new international consensus staging system and new diagnostic codes

Merkel cell carcinoma is a rare but aggressive neuroendocrine carcinoma of the skin with a rising incidence and a high mortality rate. It occurs primarily in sun-exposed skin of older individuals. It is characterized by a high rate of local recurrence, regional lymph node metastases and distant metastases, occurring even after prompt treatment. Many controversies exist regarding its pathogenesis and optimal management. The discovery of Merkel cell polyomavirus has been a major breakthrough in understanding the aetiology of the disease. A recently adopted new international consensus staging system in combination with new international diagnostic codes are expected to facilitate future clinical trials and improve the management of patients. According to recent (2010) guidelines, most patients should be managed with a combination of surgery and radiotherapy.

Age-specific seroprevalence of Merkel cell polyomavirus, BK virus, and JC virus

We produced capsids of Merkel cell polyomavirus (MCPyV) in a baculovirus expression system and developed a virus-like particle (VLP) enzyme-linked immunosorbent assay (ELISA). To determine age-specific seroprevalence, serum samples were collected from 947 individuals attending hospital outpatient clinics and ranging in age from 1 to 93 years. To evaluate the association between exposure to MCPyV and Merkel cell cancer (MCC), plasma samples were obtained from 33 MCC patients and 37 controls. MCPyV seroprevalence was 45% in children under 10 years of age, increased to 60% in the next decade of life, and peaked at 81% among those 60 to 69 years of age. Levels of MCPyV capsid antibodies were positively correlated with age (P = 0.007). Virus specificity of MCPyV seroreactivity was supported by competitive inhibition of reactivity by MCPyV VLPs and not by BK polyomavirus (BKPyV) VLPs. MCPyV seroprevalence was greater among MCC patients (91%) than controls (68%; age-adjusted P value, 0.32); the mean level of MCPyV antibodies was also greater (P = 0.04). The age-specific seroprevalence of MCPyV shares with previously known polyomaviruses, BKPyV and JC polyomavirus (JCPyV), evidence of widespread exposure in human populations beginning early in life. MCPyV age-specific seroprevalence also has unique features. Seroprevalence among children is higher than that of JCPyV but lower than that of BKPyV. Among older adults, MCPyV seroprevalence remains high, while that of BKPyV declines and that of JCPyV continues to rise. In agreement with results from other studies, we found an association between MCPyV seropositivity and MCC, and higher levels of serum MCPyV capsid antibodies in MCC patients than in controls.