Case of probable spontaneous regression of Merkel cell carcinoma combined with squamous cell carcinoma without surgical intervention.

Merkel cell carcinoma (MCC) is a rare but more lethal cutaneous cancer than melanoma. However, spontaneous regression of a number of MCC has been reported, although the cause of this regression remains unclear. In most cases, MCC regresses after a surgical procedure, for example, biopsy. Herein, we report a case of Merkel cell polyomavirus-negative MCC coincident with squamous cell carcinoma (SCC) that underwent true spontaneous regression without biopsy. One month after the patient's first visit, clinical examination revealed that the tumor had not grown, but its surface showed changes in texture and color. Histopathologically, the excised specimen was indicative of MCC coincident with SCC and showed extensive necrosis in the upper portion of the tumor, numerous caspase-3-positive apoptotic cells, an accumulation of CD68-positive foam cells and vascular invasion. These findings suggested that the tumor had regressed. We hypothesize that extensive coagulative necrosis resulting from an insufficient local blood supply triggered the shedding of some products or components of MCC and SCC, which in turn induced antitumor immunity against both lesions.

Mutation Profile of B-Raf Gene Analyzed by fully Automated System and Clinical Features in Japanese Melanoma Patients.

BRAF gene mutations have been observed in 30-50 % of malignant melanoma patients. Recent development of therapeutic intervention using BRAF inhibitors requires an accurate and rapid detection system for BRAF mutations. In addition, the clinical characteristics of the melanoma associated with BRAF mutations in Japanese patients have not been investigated on a large scale evaluation. We recently established quenching probe system (QP) for detection of an activating BRAF mutation, V600E and evaluated 113 melanoma samples diagnosed in Saga University Hospital from 1982 to 2011. The QP system includes fully automated genotyping, based on analysis of the probe DNA melting curve, which binds the target mutated site using a fluorescent guanine quenched probe. BRAF mutations were detected in 54 of 115 (47 %) including 51 of V600E and 3 of V600 K in Japanese melanoma cases. Among clinical subtypes of melanoma, nodular melanoma showed high frequency (12 of 15; 80 %) of mutation followed by superficial spreading melanoma (13 of 26; 50 %). The QP system is a simple and sensitive method to determine BRAF V600E mutation, and will be useful tool for patient-oriented therapy with BRAF inhibitors.

Large-cell neuroendocrine carcinoma of the skin: ultrastructural and immunohistochemical findings.

Large-cell neuroendocrine carcinoma (LCNEC) is an uncommon and aggressive neuroendocrine tumor, found mainly in the lung. Although LCNEC has been reported in various organs, LCNEC of the skin is extremely rare, poorly recognized and probably underestimated. Here we report a case of LCNEC of the skin, focusing on the histopathological and ultrastructural findings in detail. The patient was an 85-year-old Japanese woman presented with a mass on her right upper eyelid. Biopsy specimen showed an infiltrative mass with extension into the subcutis. Tumor cells were arranged in organoid and trabecular patterns with sheets, nests and trabecular cords. Extensive necrotic areas were observed. Most of the tumor cells were characterized by large cell size, polygonal shape, low nuclear-cytoplasmic ratio, coarse nuclear chromatin and frequent nucleoli. They were positive for CD56, NSE, AE1/AE3, CK7, and negative for CK20, TTF-1, synaptophysin and chromogranin A. A systematic radiographic examination revealed no additional neoplastic lesions other than the right upper eyelid mass. These findings suggest that the present case is a LCNEC of the skin. The existence of LCNEC in the skin should be recognized, as it is a rare variant of carcinoma that can potentially be misconstrued as a metastasis or as Merkel cell carcinoma.

Merkel cell carcinoma associated with stable chronic hemodialysis: A report of two cases.

Merkel cell carcinoma (MCC) is a rare but aggressive cutaneous malignancy associated with the Merkel cell polyomavirus (MCPyV). Multiple studies have shown that the incidence of MCC is higher among immunocompromised individuals than among the general population. In fact, immunosuppressed individuals account for approximately 10% of the MCC patient population. In this report, we describe two cases of MCPyV-related MCC in Japanese patients on hemodialysis. In both the cases, MCC was present on the face. Both cellular and humoral immunities have been shown to be decreased in uremic patients, and dialysis patients have a high risk of viral-mediated cancers, including human papillomavirus-associated cancers. Immune dysfunction related to uremia and dialysis may be associated with a high risk of developing MCC.

Merkel cell carcinoma with glandular differentiation admixed with sweat gland carcinoma and spindle cell carcinoma: histogenesis of merkel cell carcinoma from hair follicle stem cells.

We describe a unique case of Merkel cell carcinoma (MCC) with a heterogeneous differentiation exhibiting distinct triphasic phenotypic differentiation features: small cells typical of MCC, sweat gland carcinoma (sweat gland Ca.) with possible decapitation secretion, and spindle cell carcinoma (spindle cell Ca.). The patient was an 84-year-old Japanese woman. We evaluated the present case immunohistochemically with various antibodies. The histological features showed a gradual transition from MCC to sweat gland Ca. and spindle cell Ca. For clarifying the histogenesis, immunophenotypic analysis of the 3 different components of the carcinoma was performed using hair follicle stem cell markers (eg, CK15, CK19, and CD200) that have been identified as biomarkers of human bulge cells. The triphasic components immunohistochemically shared the characteristic feature of CK19 and CD200 expression. We posit that the MCC arose from hair follicle stem cells residing within the bulge area where Merkel cells are preferentially situated. Based on our findings, we recommend adding this rare neoplasm to the expanding morphological spectrum of MCC.

Histogenesis of pure and combined Merkel cell carcinomas: An immunohistochemical study of 14 cases.

The histogenesis of Merkel cell carcinoma (MCC) has remained unresolved. Moreover, one of the questions is whether pure MCC and combined MCC represent the same histogenesis and entity. The existence of combined MCC suggests that MCC likely arise from pluripotent stem cells. Merkel cells (MC) localize within the bulge area, which is populated by hair follicle stem cells. We used hair follicle stem cell markers to investigate whether MCC share certain characteristics of these stem cells. Fourteen MCC specimens were examined histologically and immunohistochemically. There were six pure MCC and eight combined MCC. In six combined MCC, both MCC components and squamous components at least focally shared the expression of one or more of cytokeratin (CK)15, CK19 and CD200, which are hair follicle stem cell markers. On the other hand, four cases of pure MCC showed partially distinct CK19 expression, but did not show CK15 and/or CD200 expression. There was a distinct difference between pure MCC and combined MCC on the expression of hair follicle stem cell markers. The normal skin expressed CK15, CK19 and CD200 in the bulge area, whereas CK15 and CD200 were absent in the MC-rich glabrous skin and touch domes. The results led us to hypothesize that combined MCC originate from the hair follicle stem cells. We postulate that combined MCC undergo multidirectional differentiation into squamous, glandular, mesenchymal and Merkel cells. Further investigation is warranted to confirm the histogenesis of pure MCC and combined MCC.

Downregulation of MHC-I expression is prevalent but reversible in Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is an aggressive, polyomavirus-associated skin cancer. Robust cellular immune responses are associated with excellent outcomes in patients with MCC, but these responses are typically absent. We determined the prevalence and reversibility of major histocompatibility complex class I (MHC-I) downregulation in MCC, a potentially reversible immune-evasion mechanism. Cell-surface MHC-I expression was assessed on five MCC cell lines using flow cytometry as well as immunohistochemistry on tissue microarrays representing 114 patients. Three additional patients were included who had received intralesional IFN treatment and had evaluable specimens before and after treatment. mRNA expression analysis of antigen presentation pathway genes from 35 MCC tumors was used to examine the mechanisms of downregulation. Of note, 84% of MCCs (total n = 114) showed reduced MHC-I expression as compared with surrounding tissues, and 51% had poor or undetectable MHC-I expression. Expression of MHC-I was lower in polyomavirus-positive MCCs than in polyomavirus-negative MCCs (P < 0.01). The MHC-I downregulation mechanism was multifactorial and did not depend solely on HLA gene expression. Treatment of MCC cell lines with ionizing radiation, etoposide, or IFN resulted in MHC-I upregulation, with IFNs strongly upregulating MHC-I expression in vitro, and in 3 of 3 patients treated with intralesional IFNs. MCC tumors may be amenable to immunotherapy, but downregulation of MHC-I is frequently present in these tumors, particularly those that are positive for polyomavirus. This downregulation is reversible with any of several clinically available treatments that may thus promote the effectiveness of immune-stimulating therapies for MCC.

Ultrastructural studies of perichromatin granules with special references to Merkel cell carcinoma.

Since it has been convincingly demonstrated that Merkel cell polyomavirus (MCPyV), a new type of virus, isolated in 2008, induces some of Merkel cell carcinoma (MCC), we searched MCPyV in specimens taken from MCC patients by electron microscopy. The purpose of this communication is to report the presence of perichromatin granules (PCGs), which can be misinterpreted as virus-like particles (VLP). Tissues from several cutaneous tumors including MCC were examined by electron microscopy (EM). EM revealed intranuclear and spherical electron-dense particles with halo, approximately 55 nm in diameter suggesting possible VLP. However, granular structures were detected in MCPyV DNA positive and also negative MCC. Moreover, the same structures were detected in the tumor cells of SCC associated with MCC, those of malignant melanoma (MM), schwannoma, and also in the lesional melanocyte, fibroblast, apoptotic cell and mitotic cell. Since MCPyV DNA could not be detected in collision MCC with SCC, MM and schwannoma, this observation could mean that the granular structures we dealt with in this report represent PCGs, but not VLP and show an absence of viral particles in MCC.

Triphasic differentiations of Merkel cell carcinoma in primary and metastatic lesions.

We present a rare case of Merkel cell carcinoma (MCC) with heterologous differentiation. The patient was an 86-year-old female patient with MCC who presented with a forearm skin tumor and left axillary lymph node swelling. Histopathologically, the malignant components of the primary and metastatic lesions showed the intermingled features of triphasic phenotype differentiation, which had distinct cell populations; MCC, sweat gland carcinoma (SGC) and malignant poorly differentiated spindle cells with myogenic differentiation were immunohistochemically showed. Moreover, an electron microscopic observation of the tumor cells revealed intracytoplasmic canaliculi and junctional structures that indicated ductal differentiation. To our knowledge, this is the first case of MCC admixed with SGC and sarcomatous components in both the primary and metastatic lesions. An immunohistochemical study, using several stem cell markers, indicated that the MCC arose from pluripotent epidermal stem cells.

Keratoacanthoma and other types of squamous cell carcinoma with crateriform architecture: classification and identification.

The terminology and classification of keratoacanthoma (KA) and other types of squamous cell carcinoma (SCC) with crateriform architecture have not been clarified. The study evaluated the clinicopathological features of 41 nodular (exo-endophytic) SCC lesions with a central keratin-filled crater, including KA (well-developed stage). The lesions were histopathologically classified into six categories: (i) KA (well-developed stage) (27 lesions); (ii) KA-like SCC (three lesions); (iii) KA with malignant transformation (three lesions); (iv) infundibular SCC (crateriform) (four lesions); (v) crateriform SCC arisen from actinic keratosis (three lesions); and (vi) crateriform Bowen's disease (one lesion). The true characteristics of KA-like SCC remain unresolved, but there are three possibilities, namely, that it is one step in the evolution of KA, it is a borderline lesion between KA and invasive SCC, or it is one form of "KA with malignant transformation". KA, KA-like SCC, KA with malignant transformation and infundibular SCC (crater form) are considered to be hair follicle-related neoplasms. In contrast, crateriform SCC arisen from actinic keratosis and crateriform Bowen's disease are SCC, which are not related either to the hair follicles or KA. From an etiological standpoint, the presented lesions in these six categories are considered to be mixed up due to the similarity of crateriform architecture between the various types of lesions. However, the information provided in this report is intended to help physicians to make an accurate differential diagnosis of these conditions in clinical practice. The present study provides an opportunity to standardize the terminology for KA and related neoplasms.

Diagnostic biopsy does not commonly induce intratumoral CD8 T cell infiltration in Merkel cell carcinoma.

BACKGROUND: Merkel cell carcinoma is a polyomavirus-associated cancer that is strongly linked with T lymphocyte immune suppression in epidemiologic studies. CD8+ T cell infiltration into MCC tumors (intratumoral) has recently been shown to be strongly predictive of improved survival. In contrast, the presence of CD8+ T cells at the border of the tumor (peritumoral) had no independent prognostic value. Spontaneous regression has been reported for MCC approximately one thousand times more often than would be expected given the frequency of this cancer. Many of these events began shortly after biopsy, and in some cases lymphocytic infiltration was described. METHODOLOGY/PRINCIPAL FINDINGS: To determine whether CD8+ lymphocyte infiltration in MCC tumors is commonly altered by biopsy.33 MCC patients who had microscopic confirmation of MCC on both an initial biopsy and a re-excision specimen were included in this study. Intratumoral and peritumoral CD8 lymphocyte infiltration was quantitated using immunohistochemistry and compared using the paired t-test in biopsy versus re-excision samples. There was a trend toward increased CD8 infiltration after biopsy in a peritumoral ('stalled') pattern (p = 0.08), however, biopsy was not associated with a significant increase in CD8 T cells in the clinically more important intratumoral location (p = 0.58). CONCLUSIONS/SIGNIFICANCE: The initial diagnostic biopsy for MCC does not commonly alter intratumoral CD8+ T cell infiltration, suggesting it does not directly induce immunologic recognition of this cancer. Because CD8 infiltration is typically stable after biopsy, this parameter may be useful to assess the efficacy of future immune therapies for this virus-associated, immunogenic, often-lethal cancer.

Transcriptome-wide studies of merkel cell carcinoma and validation of intratumoral CD8+ lymphocyte invasion as an independent predictor of survival.

PURPOSE: Merkel cell carcinoma (MCC) is a polyomavirus-associated skin cancer that is frequently lethal and lacks established prognostic biomarkers. This study sought to identify biomarkers that improve prognostic accuracy and provide insight into MCC biology. PATIENTS AND METHODS: Gene expression profiles of 35 MCC tumors were clustered based on prognosis. The cluster of genes overexpressed in good-prognosis tumors was tested for biologic process enrichment. Relevant mRNA expression differences were confirmed by quantitative polymerase chain reaction and immunohistochemistry. An independent set of 146 nonoverlapping MCC tumors (median follow-up, 25 months among 116 living patients) was employed for biomarker validation. Univariate and multivariate Cox regression analyses were performed. RESULTS: Immune response gene signatures were prominent in patients with good prognoses. In particular, genes associated with cytotoxic CD8+ lymphocytes were overexpressed in tumors from patients with favorable prognoses. In the independent validation set, cases with robust intratumoral CD8+ lymphocyte infiltration had improved outcomes (100% MCC-specific survival, n = 26) compared with instances characterized by sparse infiltration (60% survival, n = 120). Only stage and intratumoral CD8 infiltration (but not age, sex, or CD8+ lymphocytes localized to the tumor-stroma interface) were significant in both univariate and multivariate Cox regression analyses. Notably, traditional histologic identification of tumor-infiltrating lymphocytes was not a significant independent predictor of survival. CONCLUSION: Intratumoral CD8+ lymphocyte infiltration can be readily assessed on paraffin-embedded tissue, is independently associated with improved MCC-specific survival, and therefore, may provide prognostic information that enhances established MCC staging protocols.