The Toker Tumor

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.

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.

Reproducible Histopathologic Features in Cases of Basal Cell Carcinoma With Neuroendocrine Expression: A Clinicopathologic Study of 24 Cases With a Potential Diagnostic Pitfall

ABSTRACT

Basal cell carcinomas (BCCs) are common malignancies that usually show clear histomorphologic features, but in certain instances, it can display different patterns of differentiation leading to potential diagnostic confusion. BCCs with neuroendocrine differentiation/expression have been mentioned only briefly in the literature. In this study, we present cases of BCCs with neuroendocrine differentiation/expression that demonstrate reproducible histopathological features. Twenty-four cases were included in the study. All tumors showed conventional histopathologic features that are seen in BCCs, but in addition, all the tumors showed large, hyperchromatic, pleomorphic, mononuclear, and multinucleate cells with intracytoplasmic inclusions and intranuclear cytoplasmic invaginations, with rare cases showing stippled nuclei (salt-and-pepper appearance). These histologic features were somewhat concerning for a neuroendocrine carcinoma; thus, immunohistochemistry studies were performed in all cases at the time of diagnosis. By immunohistochemistry, all tumors showed expression of neuroendocrine markers. CD56 was expressed in all cases 24/24, chromogranin was positive in 17/24 cases, and synaptophysin 8/24 was positive in cases. This study confirms a subset of histopathologic features that are present in cases of BCC that are associated with neuroendocrine expression that can potentially be interpreted differently and can create a diagnostic pitfall. Neuroendocrine expression in BCCs is yet uncertain, and further studies are required to fully understand this phenomenon. To avoid diagnostic pitfalls, dermatopathologists must be aware of these unusual histopathologic features and aberrant immunostaining in such tumors; hence, it is advised to perform a thorough histologic inspection.

Predictors of survival in neurometastatic Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is a rare cutaneous malignancy of neuroendocrine origin, with about 30 cases of brain metastasis (BM) reported in the literature. Historically, the treatment of neurometastatic MCC has largely included chemotherapy and radiotherapy. The aim was to investigate predictors of overall survival (OS) in neurometastatic MCC.

METHODS

In this retrospective study, we surveyed institutional databases and conducted a systematic review of the literature to identify cases reporting on management of distant MCC BM. A pooled survival analysis was performed on the institutional and literature cases to assess predictors of OS.

RESULTS

Forty cases were included for analysis, describing operative [14] and non-operative [26] management. Median time to central nervous system involvement was 17.0-mos (interquartile range 10.5-26.5), and most patients had a single BM (62.5%). Management of intracranial disease included radiotherapy (82.5%), systemic therapy (59.5%) and surgical resection (35%). Operative management was associated with a lower intracranial burden of disease (BoD), but similar systemic BoD. Both neurosurgery (hazard ratio [HR] 0.18, 95% confidence interval [CI]: 0.06-0.54, p = 0.002), having RT (HR 0.37, 95% CI: 0.14:0.93, p = 0.04) and having a single BM (extensive intracranial BoD: HR 2.51, 95% CI: 1.12-5.6, p = 0.03) conferred an OS benefit on risk-unadjusted analysis. Only, neurosurgical resection was an independent predictor of OS (HR 0.12, 95% CI: 0.03-0.49, p = 0.003), controlling for age, BoD and radiotherapy.

CONCLUSIONS

Resection of MCC BM may confer a survival benefit given appropriate patient selection. Prospective investigation of multimodal management of neurometastatic MCC is warranted, especially given the promise of new immunotherapy agents in treating MCC.

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.

Histologic Mimics of Basal Cell Carcinoma

CONTEXT

- Basal cell carcinoma (BCC) is the most common human malignant neoplasm and is a frequently encountered diagnosis in dermatopathology. Although BCC may be locally destructive, it rarely metastasizes. Many diagnostic entities display morphologic and immunophenotypic overlap with BCC, including nonneoplastic processes, such as follicular induction over dermatofibroma; benign follicular tumors, such as trichoblastoma, trichoepithelioma, or basaloid follicular hamartoma; and malignant tumors, such as sebaceous carcinoma or Merkel cell carcinoma. Thus, misdiagnosis has significant potential to result in overtreatment or undertreatment.

OBJECTIVE

- To review key features distinguishing BCC from histologic mimics, including current evidence regarding immunohistochemical markers useful for that distinction.

DATA SOURCES

- Review of pertinent literature on BCC immunohistochemistry and differential diagnosis.

CONCLUSIONS

- In most cases, BCC can be reliably diagnosed by histopathologic features. Immunohistochemistry may provide useful ancillary data in certain cases. Awareness of potential mimics is critical to avoid misdiagnosis and resulting inappropriate management.

Update on Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous neuroendocrine malignancy. Merkel cell polyomavirus, a tumorigenic DNA virus, is present in most MCC tumors, with implications for tumor biology, diagnosis, and management. Merkel cell polyomavirus-negative tumors have a high burden of UV-signature mutations, similar to melanoma. The histopathologic diagnosis of MCC requires immunohistochemistry to exclude morphologically similar entities. Therapies for advanced disease are currently lacking. Here, the features of MCC are reviewed, including recent molecular discoveries with implications for improved therapy for advanced disease.

Update on Merkel Cell Carcinoma: Epidemiology, Etiopathogenesis, Clinical Features, Diagnosis, and Staging

Merkel cell carcinoma (MCC) is a rare, highly aggressive tumor, and local or regional disease recurrence is common, as is metastasis. MCC usually develops in sun-exposed skin in patients of advanced age. Its incidence has risen 4-fold in recent decades as the population has aged and immunohistochemical techniques have led to more diagnoses. The pathogenesis of MCC remains unclear but UV radiation, immunosuppression, and the presence of Merkel cell polyomavirus in the tumor genome seem to play key roles. This review seeks to update our understanding of the epidemiology, etiology, pathogenesis, and clinical features of MCC. We also review histologic and immunohistochemical features required for diagnosis. MCC staging is discussed, given its great importance in establishing a prognosis for these patients.

Merkel cell carcinoma: case study and literature review

Merkel cell carcinoma is a rare, aggressive, highly metastatic, often fatal, primary neuroendocrine tumor typically located on sun-exposed skin. It is frequently found in white males aged 60 to 70 years. The somewhat typical benign clinical appearance of the lesion can result in a delayed diagnosis, leading to a less than optimal outcome.

Merkel cell carcinoma with divergent differentiation: histopathological and immunohistochemical study of 15 cases with PCR analysis for Merkel cell polyomavirus

AIMS

To report on 15 cases of Merkel cell carcinoma (MCC) with divergent differentiation, to characterize its clinicopathological spectrum and its relationship with Merkel cell polyomavirus (MCV).

METHODS AND RESULTS

Fifteen patients with a mean age of 81 years were included. Follow-up was available for 13 cases (range 12 days to 6 years; median 6 months). Recurrence, metastasis and mortality rates were 15.4%, 53.8% and 61.5%, respectively. All tumours showed the typical histological and immunohistochemical features of MCC, with at least one additional divergent component. Eight cases had a single aberrant component (squamous in six cases, follicular in one case, and porocarcinoma in one case), six cases had two aberrant components (squamous and sarcomatous in three cases, glandular and squamous in two cases, and sarcomatous and neuroblastic in one case), and one case had three aberrant components (glandular, squamous, and sarcomatous). All cases had dysplastic changes in the overlying epithelium, and four of 15 showed epidermotropism. PCR analysis for Merkel cell polyomavirus (MCV) gave negative results in all 12 cases tested.

CONCLUSIONS

Merkel cell carcinoma with divergent differentiation is a highly aggressive tumour that might be difficult to recognize, owing to its wide histological variability. Negativity for MCV suggests that the virus is not implicated in the development of this subtype of MCC.

Human Merkel cell polyomavirus: virological background and clinical implications

The Merkel cell polyomavirus (MCPyV), identified in humans in 2008, is associated with a relatively rare but aggressive neuroendocrine skin cancer, the Merkel cell carcinoma (MCC). MCC incidence is increasing due to the advancing age of the population, the increase in damaging sun exposure and in the number of immunocompromised individuals. MCPyV must be considered as the etiological agent of MCC and thus is the first example of a human oncogenic polyomavirus. MCPyV infection is common, and seroprevalence studies indicate that widespread exposure begins early in life. The majority of adults have anti-MCPyV antibodies and there is a growing body of evidence that healthy human skin harbors resident or transient MCPyV suggesting that MCPyV infection persists throughout life. However, the mode of transmission, the host cells, and the latency characteristics of this virus remain to be elucidated. In addition, it is still not clear whether MCPyV is associated with diseases or lesions other than Merkel cell carcinoma. The etiologic role of MCPyV in MCC opens up opportunities to improve the understanding of this cancer and to potentially improve its treatment.

Distinct gene expression profiles of viral- and nonviral-associated merkel cell carcinoma revealed by transcriptome analysis

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine tumor with high mortality rates. Merkel cell polyomavirus (MCPyV), identified in the majority of MCC, may drive tumorigenesis via viral T antigens. However, mechanisms underlying pathogenesis in MCPyV-negative MCC remain poorly understood. To nominate genes contributing to pathogenesis of MCPyV-negative MCC, we performed DNA microarray analysis on 30 MCCs. MCPyV status of MCCs was determined by PCR for viral DNA and RNA. 1593 probe-sets were differentially expressed between MCPyV-negative and -positive MCC, with significant differential expression defined as at least 2-fold change in either direction and p-value of ≤ 0.05. MCPyV-negative tumors showed decreased RB1 expression, whereas MCPyV-positive tumors were enriched for immune response genes. Validation studies included immunohistochemistry demonstration of decreased RB protein expression in MCPyV-negative tumors and increased peritumoral CD8+ T lymphocytes surrounding MCPyV-positive tumors. In conclusion, our data suggest that loss of RB1 expression may play an important role in tumorigenesis of MCPyV-negative MCC. Functional and clinical validation studies are needed to determine whether this tumor suppressor pathway represents an avenue for targeted therapy.

Merkel cell carcinoma--pathogenesis, clinical aspects and treatment

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine carcinoma of the skin demonstrating a high rate of recurrence and metastasis. Indeed, 5-year rates for MCC specific survival are only about 60%. Although MCCs' incidence is rapidly increasing, it is still a very rare tumour. In this regard, the American Cancer Society had estimated for 2008 almost 1500 new cases in the USA. Recently, the newly identified Merkel cell polyomavirus has been found associated with most of the MCC cases. Nevertheless, the pathogenesis of MCC is not yet fully understood. Here, we will summarize recent findings of the pathogenesis of MCC, present an overview of clinical aspects and discuss treatment options for MCCs.

Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine carcinoma of the skin. The incidence of this rare tumor is increasing rapidly; the American Cancer Society estimates for 2008 almost 1500 new cases in the USA. Thus, the incidence of MCC will exceed the incidence of cutaneous T-cell lymphoma. Moreover, the mortality rate of MCC at 33% is considerably higher than that of cutaneous melanoma. These clinical observations are especially disturbing as we are only recently beginning to understand the pathogenesis of MCC. For the same reason, the therapeutic approach is often unclear; reliable data are only available for the therapy of locoregional disease.

Expression of TdT in Merkel cell carcinoma and small cell lung carcinoma

Merkel cell carcinoma (MCC) is an uncommon tumor with indistinct clinical features. The differential diagnosis includes small cell lung carcinoma (SCLC). We characterized the expression of terminal deoxynucleotidyl transferase (TdT) and a panel of immunohistochemical markers in 40 MCC, 30 SCLC, and 6 pulmonary carcinoid tumor (PCT) cases. We used antibodies against TdT, thyroid transcription factor (TTF)-1, cytokeratins (CKs) 7 and 20, chromogranin, and synaptophysin. Immunostaining was recorded semiquantitatively. Of 40 MCC cases, 28 (70%) were positive for TdT, showing, on average, more than 25% of tumor cells reactive with moderate nuclear staining intensity. TTF-1 (1 [3%]), CK7 (2 [5%]), CK20 (35 [88%]), chromogranin (29 [73%]), and synaptophysin (39 [98%]) were expressed in the MCCs. Of the 5 CK20- MCC cases, 4 were positive for TdT. SCLC showed expression of TTF-1 (23/30 [77%]), CK7 (22/30 [73%]), chromogranin (16/30 [53%]), and synaptophysin (22 [73%]) and no CK20 (0%) expression. Of 30 SCLC cases, 2 (7%) were positive for TdT. TdT may be beneficial in rare cases of CK20- MCC and may assist in distinguishing between MCC and SCLC. There is significant immunohistochemical variability and overlap between these 2 tumors.

Updated Review of the Pathogenesis and Management of Merkel Cell Carcinoma

Background:

Merkel cell carcinoma is a rare, aggressive, malignant cutaneous tumor of the elderly or immunosuppressed individuals that usually appears on sun-exposed areas of the body. Its pathogenesis is still debated, and, currently, no standardized treatment exists.

Objective:

To provide a current updated review of the most relevant data concerning the pathogenesis and management of Merkel cell carcinoma.

Methods:

Using relevant MeSH terms, we performed a review of the literature on these subjects from 1980 to June 2009.

Results and Conclusion:

The current management of Merkel cell carcinoma is based on surgical excision as the majority of patients present with localized disease, whereas up to 30% have regional lymph node metastases. In these cases, the best outcome is achieved with multidisciplinary management that includes radiotherapy. Chemotherapy is part of the treatment in advanced cases and is mandatory for distant metastatis. Given that a recent work showed the presence of a previously unknown polyomavirus, which the authors called Merkel cell polyomavirus, the therapeutical approach to Merkel cell carcinoma could be reconsidered in the future.

Merkel cell polyomavirus: a specific marker for Merkel cell carcinoma in histologically similar tumors

The recently described Merkel cell polyomavirus (MCPyV) is reportedly present in 50% to 80% of Merkel cell carcinomas (MCC). Although the virus has been shown to be absent from other cutaneous neoplasms, its association with malignancies that are histologically similar to MCC, specifically small cell carcinoma of the lung and other high-grade neuroendocrine tumors, has yet to be thoroughly investigated. To address this issue, we identified a set of 74 cases of visceral high-grade neuroendocrine tumors from a variety of anatomic sites, including 32 cases from the lung, 16 cases from the gastrointestinal tract, 20 cases from the female reproductive system, 3 cases from soft tissue, 2 cases from the head and neck region, and 1 case from the bladder. Using a set of primers optimized to detect MCPyV in formalin-fixed tissue, polymerase chain reaction (PCR)-based testing showed evidence of MCPyV DNA in only 1 of the 74 tumors; however, clinicopathologic review of the positive case (a neuroendocrine tumor of the small intestine) disclosed that the patient had a history of primary MCC of the buttock. PCR-based testing also showed no evidence of the related WU and KI polyomaviruses in the set of 74 cases. We conclude that, when evaluated by PCR-based testing, MCPyV is a specific marker for MCC that can be helpful in distinguishing cases of metastatic MCC from other high-grade neuroendocrine tumors. Our results also suggest that MCPyV does not have a role in the oncogenesis of visceral high-grade neuroendocrine tumors.

Merkel cell polyomavirus expression in merkel cell carcinomas and its absence in combined tumors and pulmonary neuroendocrine carcinomas

Merkel cell carcinoma (MCC) is the eponym for primary cutaneous neuroendocrine carcinoma. Recently, a new polyoma virus has been identified that is clonally integrated in the genome of the majority of MCCs, with truncating mutations in the viral large T antigen gene. We examined the presence of Merkel cell polyomavirus (MCV) in a set of 17 frozen tumor samples by quantitative polymerase chain reaction; 15 of them (88%) were positive. Sections from corresponding archival material were analyzed by immunohistochemistry (IHC) with the novel monoclonal antibody CM2B4, generated against a predicted antigenic epitope on the MCV T antigen, and tested for the expression of cytokeratin 20 (CK20). Sufficient archival material for IHC was available in only 15 of the 17 cases whose frozen tissue samples had been studied by polymerase chain reaction. Of the 15 tumors analyzed immunohistochemically, 10 (67%) showed positive labeling with CM2B4, 14 (93%) expressed CK20. A tissue microarray of 36 MCCs, 7 combined squamous and neuroendocrine carcinomas of the skin, and 26 pulmonary neuroendocrine carcinomas were also examined by IHC. Of the 36 MCCs assembled on a microarray, 32 (89%) tumors expressed CK20, and 27 (75%) were immunoreactive with CM2B4. The skin tumors with a combined squamous and neuroendocrine phenotype and all pulmonary neuroendocrine carcinomas failed to react with CM2B4. Our study shows that CM2B4 is a useful reagent for the diagnosis of MCC. It labels the majority of MCCs, but fails to react with pulmonary neuroendocrine carcinomas. We also found that neuroendocrine carcinomas of the skin arising in association with a squamous cell carcinoma seem to be independent of MCV.

Merkel cell carcinoma: review

Merkel cell carcinoma (MCC) is synonymous with primary cutaneous neuroendocrine carcinoma. It tends to affects elderly whites, but there is also an increased incidence among immunosuppressed patients. The recent identification of a novel polyomavirus associated with the tumor has stimulated renewed interest in its pathogenesis. MCC tends to show classic histologic features of a neuroendocrine carcinoma and is often positive for CK20, but nonclassic cytologic findings and unusual immunophenotypes may be observed and can lead to a diagnostic confusion. MCC needs to be distinguished from other primary cutaneous tumors with a small cell appearance and metastatic tumors. Surgical excision is the treatment of choice, but radiation therapy has also found to be effective. Sentinel lymph node biopsy has become an integral part of the staging of patients with MCC.

Clinical course and prognostic factors of Merkel cell carcinoma of the skin

BACKGROUND

Merkel cell carcinoma (MCC) is a rare neuroendocrine malignancy of the skin first described by Toker as 'trabecular carcinoma of the skin' in 1972. To date, the origin of the tumour cells still remains unclear.

OBJECTIVES

The present study analyses prognostic factors of MCC.

PATIENTS AND METHODS

The medical records of 57 patients with MCC treated between 1988 and 2006 at the Department of Dermatology in Tübingen were reviewed.

RESULTS

We identified 26 (45.6%) male and 31 (54.4%) female patients with MCC; the age at diagnosis ranged from 26 to 97 years (median 71 years). Primary tumours were located mainly on the head and neck areas (27 cases, 47.4%) and upper extremities (14 cases, 24.6%); 11 tumours were found on the lower extremities (19.3%) and four lesions on the chest (7%); one patient had an unknown primary location. Forty-five (78.9%) patients were diagnosed at stage I of the disease, 11 (19.3%) at stage II, and one patient (1.8%) at stage III at initial presentation. Stage of the disease and age at initial presentation were statistically significant with regard to overall (P < 0.0001; P = 0.0327) and tumour-specific survival (P < 0.0001; P = 0.0156). Use of the Cox regression model revealed initial stage of the disease as the only significant factor in the multivariate analysis. Radiotherapy applied promptly after excision of the primary tumour extended the time to progression significantly (P = 0.0376) but did not prolong overall or tumour-specific survival. Other parameters such as sex, site of tumour, sentinel node biopsy, excision margins, skin and noncutaneous malignancies were found to be not significant.

CONCLUSIONS

Currently, early recognition of the disease seems to be the only method of ensuring overall survival. However, evidence-based treatment modalities are still urgently needed.

Prevalence of Merkel cell polyomavirus in Merkel cell carcinoma

It has recently been shown that Merkel cell carcinoma, a rare and often lethal cutaneous malignancy, frequently harbors a novel clonally integrated polyomavirus aptly named Merkel cell polyomavirus. We aimed to study the prevalence of Merkel cell polyomavirus in cases of Merkel cell carcinoma, using specimens from formalin-fixed, paraffin-embedded tissue blocks. In our archives we identified 41 cases of Merkel cell carcinoma (from 29 different patients). Of these, 20 cases were primary cutaneous tumors, 4 were local recurrences, and 17 were metastases. PCR using two previously published primer sets, LT1 (440 bp amplicon) and LT3 (308 bp amplicon), as well as a novel primer set MCVPS1 (109 bp amplicon), was performed on all cases. Selected PCR products were sequenced to confirm amplicon identity. In addition, the MCVPS1 products were digested with BamH1, yielding an 83 bp product. Amplifiable DNA was recovered in all 41 study cases. The detection rate of Merkel cell polyomavirus for each of the three primer sets was 22 of 29 patients (76%) for MCVPS1, 12 of 29 (41%) for LT3, and 8 of 29 (28%) for LT1. The variation between primer set detection rates was largely due to poor DNA quality, as supported by poor amplification of the higher molecular weight markers in size control ladder products and the fact that all cases that were positive by LT1 and LT3 were positive by MCVPS1. Our findings provide further evidence to link Merkel cell polyomavirus with a possible role in the oncogenesis of Merkel cell carcinoma. On a more practical level, our paraffin-optimized primer set may be used as an ancillary test to confirm the diagnosis of Merkel cell carcinoma in the clinical setting or for screening other rare tumor types for the causative virus, especially those tumor types that are underrepresented in frozen tissue repositories.

Merkel cell carcinoma: molecular pathogenesis, clinical features and therapy

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine carcinoma of the skin. The incidence of this rare tumor is increasing rapidly; the American Cancer Society estimates for 2008 almost 1500 new cases in the U.S. Thus, the incidence of MCC will exceed the incidence of cutaneous T-cell lymphoma. Moreover, the mortality rate of MCC with 33% is considerably higher than that of cutaneous melanoma. These clinical observations are especially disturbing as we are only recently beginning to understand the pathogenesis of MCC. For the same reason, the therapeutic approach is often unclear; reliable data are only available for the therapy of locoregional disease.

Vascular changes in merkel cell carcinoma based on a histopathological study of 92 cases

Although prominent vascular proliferation is a known feature of various neuroendocrine tumors, it has not been systematically studied in Merkel cell carcinoma (MCC) of the skin. The purpose of this study was to fully characterize the light microscopic, immunohistochemical, and ultrastructural features of vascular changes associated with MCC and to determine their frequency and differential diagnostic implications. Additionally, the presence of human herpesvirus 8 DNA in the lesional tissue was investigated. Of 92 studied cases of MCC, 18 cases (20%) were found to exhibit foci of prominent vascular changes which were classified into the following 6 patterns: pericyte hyperplasia, pyogenic granuloma-like, hemangioendothelioma-like, epithelioid hemangioma-like, peliosis-like, and follicular dendritic cell tumor-like pattern. In addition, Azzopardi phenomenon was observed. These changes occurred singly or in combination. Human herpesvirus 8 DNA was identified by polymerase chain reaction in none of the 18 cases. It is concluded that prominent vascular proliferations may be seen in 20% of MCC, and thereby, MCC resembles neuroendocrine tumors in other organs. When unduly prominent and encountered in a limited biopsy specimen, vascular alterations may represent a potential diagnostic pitfall, but, on the other hand, they themselves may serve as a clue to the correct diagnosis. Human herpesvirus 8 does not play a role in angiogenesis in MCC.

Application of immunohistochemistry to the diagnosis of primary and metastatic carcinoma to the lung

CONTEXT

Immunohistochemistry is a very valuable and often used tool in the differential diagnosis of lung carcinomas whether primary or secondary to the lung. The most useful application is in distinguishing primary lung tumors from metastatic tumors to the lung from common sites (colon, breast, prostate, pancreas, stomach, kidney, bladder, ovaries, and uterus). Immunohistochemistry also aids in the separation of small cell carcinoma from non-small cell carcinoma and carcinoids particularly in small biopsy specimens limited by artifact. Although there is no "lung-specific tumor marker," with the help of a relatively restricted marker, thyroid transcription factor 1, it is possible to separate a lung primary from a metastasis with a reasonable degree of certainty. Another lung-specific marker on the horizon is napsin A, which appears to complement thyroid transcription factor 1 in defining a lung primary.

OBJECTIVE

To present a practical review and to critique commonly used markers in the differential diagnosis of lung neoplasms and to list valuable immunohistochemical prognostic markers that the pathologist is called on to perform and interpret.

DATA SOURCES

A comprehensive PubMed data search and personal practical experience.

CONCLUSIONS

With a panel of immunohistochemical markers, it is possible to distinguish or narrow down most lung neoplasms and separate them into meaningful therapeutic categories. In the future as more proteomic and genomic data surface, immunohistochemical markers to newly discovered antigens may become a routine part of prognostication.

Large-cell neuroendocrine carcinoma of the skin, with lymphoid stroma

We report two cases of a large-cell neuroendocrine carcinoma of the skin as a distinct histological category. The patients are a 63-year-old woman with a 7-mm reddish round nodule on her nose for 4 months, and a 95-year-old man with several hemorrhagic nodules on the external ear for 28 months. The first patient had two positive sentinel lymph nodes. The tumors from both patients consisted of islands of pleomorphic large cells within a lymphoid stroma.

An unusual case of Merkel cell carcinoma

PURPOSE

Merkel cell carcinoma (MCC) is a rare aggressive neuroendocrine tumor of the skin mainly found in elderly white patients. Due to its poor prognosis with distant metastases in up to 33% and local recurrence in 25-33% and a 5 year disease-specific survival of 64% (1-2) its early diagnosis and appropriate treatment is mandatory.

METHODS

The study is an exceptional clinical case of a patient with a large inoperable MCC unable to be treated according to treatment guidelines due to her old age. We review the literature addressing treatment options.

RESULTS

The patient was treated with palliative definitive radiotherapy to her large MCC of the left lower leg. She showed a rapid clinical response to four palliative radiation doses of 7 Gy each, necrosis of tumor mass and persistent clearing at a follow-up of 32 weeks. Our patient was very unusual in terms of her extensive MCC and her rapid and complete response to palliative radiotherapy lasting for 6 months at present.

CONCLUSIONS

As MCC is an aggressive tumor, best survival is achieved with early diagnosis in a localized stage and prompt adequate surgery and further stage-adjusted treatment. Thus, the differential diagnosis of MCC should not be dismissed in a reddish nodule on the leg, and every excision should be submitted to pathology. In accordance with the literature we demonstrate here that definitive radiotherapy is an effective treatment option for inoperable MCC, which in this individual patient produced necrosis of the extensive tumor mass after only four palliative doses.