Merkel cell carcinoma. Histopathology, immunohistochemistry, and cytogenetic analysis

Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare and extremely aggressive neuroendocrine carcinoma of the skin, with increasing incidence worldwide. This review intends to propose a comprehensive evaluation of MCC epidemiology, clinical features, pathogenetic mechanisms, diagnosis, and therapies. A section is dedicated to immunological aspects and another to the involvement of angiogenesis and angiogenic growth factors in MCC progression, proposing novel diagnostic and therapeutic approaches. Advanced MCC tumors have been treated with immune checkpoint inhibitors with effective results. Therefore, the state of art of this immunotherapy is also examined, reporting on the most recent clinical trials in the field. We conclude by underlining the achievements in the understanding of MCC pathology and indicating the present needs for effective diagnosis and therapeutic management of the disease.

A short-term in vivo model for Merkel Cell Carcinoma

In vivo tumor models are essential for studying the biology of cancer, identifying tumor targets and evaluating antitumor drugs. Considering the request for the minimisation of animal experiments and following the "3R"-rule ("replacement," "refinement," "reduction"), it has become crucial to develop alternative experimental models in cancer biology. Several studies have already described the avian chorioallantoic membrane (CAM) model as an alternative to rodents, suitable to investigate growth, progression and metastasis of various types of cancer. In the present work, we grafted three Merkel cell carcinoma (MCC) cell lines onto the avian CAM and monitored tumor growth and development of solid tumor nodules. Morphology of xenograft was characterised histologically and immunohistochemically. Our results demonstrate CAM assay as a useful tool to study MCC pathophysiology.

The immunohistochemical characterization of devil facial tumor disease (DFTD) in the Tasmanian Devil (Sarcophilus harrisii)

Immunohistochemical techniques were used to characterize the disfiguring and debilitating fatal neoplastic disease, devil facial tumor disease (DFTD), which has recently affected a significant proportion of the wild population of Tasmanian Devils (Sarcophilus harrisii). The diagnostic values of a number of immunohistochemical stains were employed to further characterize 50 representative cases. The neoplasms were negative for cytokeratin (0/48), epithelial membrane antigen (0/42), von Willebrand factor (vWF) (0/11), smooth muscle actin (SMA) (0/26), desmin (0/47), glial fibrillary acid protein (0/13), CD16 (0/13), CD57 (0/43), CD3 (0/18), and LSP1 (0/16). DFTD cells were positive for vimentin (50/50), S-100 (41/48), melan A (11/39), neuron specific enolase (35/35), chromogranin A (12/12) and synaptophysin (29/30). The cells were negative for amyloid (0/30) and stained negatively with Singh's silver (0/34) but were weakly argyrophilic (3/40) using Grimelius histochemical stain. These staining characteristics are consistent with cells of neuroectodermal origin.

The Toker Tumor

Primary neuroendocrine carcinoma of the skin is a relatively rare tumor that was first described by Cyril Toker in 1972. Since the seminal paper by Toker based on simple morphologic observations and detailed clinical correlation, our understanding of the clinical, morphological, and biological attributes of these lesions has grown exponentially with their increased awareness by pathologists and clinicians as well as with the many contributions of modern diagnostic techniques. The present review focuses principally on the various morphologic appearance that these tumors are able to adopt, the role of modern special techniques for diagnosis, and the conditions that need to be considered in their differential diagnosis.

Immunohistochemical study of apoptosis markers and involvement of chemokine CXCR4 in skin Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is a rare, aggressive cancer of the skin that mainly affects elderly patients. Because of its rarity, there is no established treatment or proven markers to guide therapy or prognosis. Immunohistochemical expression of apoptosis proteins is considered a useful marker of both malignancy and tumour progression. Apoptosis plays a fundamental role in skin homeostasis, and apoptotic cells have been detected in normal and diseased skin. Chemokines possess a wide range of biological activities and CXCR4 is expressed in some cancer cells, where it plays an efficient role in metastasis formation.

OBJECTIVE

To identify immunohistochemical parameters that can help clinicians select the most suitable therapy for skin MCC.

DESIGN

Antibodies against ki67, bcl-2, p53, survivin, p16 and CXCR4 were tested to assess the usefulness of these antigens as indices of proliferation potential and predictors of prognosis.

METHODS

Immunohistochemical detection of apoptosis inhibitors and CXCR4 was performed on tissue from 12 patients with primary MCC. After excision of the primary lesion, five survived and had no metastases, and seven experienced local recurrence or lymph node metastases.

RESULTS

Expression of ki67 and survivin was increased in patients with local recurrence or metastasis (retrospectively classified as 'poor prognosis') compared with those with a 'good prognosis', and bcl-2 expression was significantly greater (P=0.003). P53 and p16 immunostaining was moderate in both groups. A positive correlation was observed between survivin and mutant p53 in the poor prognosis group (r=0.593, P=0.033; regression coefficient). High values of p53 were measured in patients with high levels of survivin and vice versa. CXCR4 was not detected at all.

CONCLUSIONS

Our results show strong MCC cell apoptosis inhibition and a high cell proliferation capacity. The positive correlation between survivin and p53 may be a predictor of MCC spread via the lymphatic network. Absent CXCR4 expression may reflect a less aggressive form, with less efficient development of distant and non-organ-selective metastasis formation.

Combined karyotyping, CGH and M-FISH analysis allows detailed characterization of unidentified chromosomal rearrangements in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a rare aggressive neuroendocrine tumor of the skin. Cytogenetic studies have indicated that deletions and unbalanced translocations involving chromosome 1 short arm material occur in 40% of the investigated cases. Recurrent chromosomal imbalances detected by comparative genomic hybridization (CGH) analysis were loss of 3p, 10q, 13q and 17p and gains of 1q, 3q, 5p and 8q. In order to study genomic aberrations occurring in MCC in further detail, we combined karyotyping, CGH and multiplex-fluorescence in situ hybridization (M-FISH), a strategy that proved to be successful in the analysis of other malignancies. Analysis of 6 MCC cell lines and 1 MCC tumor revealed mostly near-diploid karyotypes with an average of 5 chromosomal rearrangements. The observed karyotypic changes were heterogeneous, with 3-27 breakpoints per case, leading to imbalance of the involved chromosomal regions that was confirmed by CGH. Chromosomal rearrangements involving the short arm of chromosome 1, the long arm of chromosome 3 and gain of 5p material were the most frequently observed abnormalities in our study. In keeping with previous observations, this series of MCCs showed no evidence for high-level amplification. We provid a detailed description of chromosomal translocations occurring in MCC that could be useful to direct future intensive investigation of these chromosomal regions.

Clear cell atypical fibroxanthoma:a clinicopathologic study

INTRODUCTION

The atypical fibroxanthoma (AFX) is considered by most authorities to represent a superficial or minimally invasive variant of malignant fibrous histiocytoma that most often presents as a solitary nodule on the sun-exposed skin of the elderly. Among the rarest variants is the clear cell AFX, a lesion which raises consideration to a differential diagnosis encompassing a variety of neoplastic and non-neoplastic clear cell proliferations.

METHODS

We describe three cases of a distinctive cutaneous neoplasm arising in the sun-exposed skin of elderly patients. In all cases, formalin-fixed, paraffin-embedded tissue was available for analysis. The histology in concert with the immunophenotype was held to be diagnostic of the clear cell variant of AFX.

RESULTS

All tumors comprised sheets of large cells with foamy cytoplasms and hyperchromatic, polyploid nuclei manifesting frequent and atypical mitoses. The critical cells in our cases expressed CD68 but none of CD3, CD20, CD34, S-100 protein, muscle-specific actin, factor XIIIa, Melan-A, carcinoembryonic antigen, or cytokeratin.

CONCLUSION

Although typical examples of AFX provoke diagnostic consideration of spindle cell cancers of the skin (most often spindle cell melanoma, spindle cell squamous cell carcinoma, and leiomyosarcoma), the clear cell variant raises other differential diagnostic considerations instead. These include balloon cell melanoma, sebaceous carcinoma, pleomorphic liposarcoma, chordoma, parachordoma, tricholemmal carcinoma and clear cell squamous cell carcinoma. A diagnosis of AFX is one of exclusion; one must employ immunohistochemical markers to rule out the aforementioned differential diagnostic considerations. By reporting the fifth, sixth and seventh cases of clear cell AFX, we hope to alert dermatopathologists to this distinctive and unusual neoplasm, recognition of which is essential to avoid under- or over-diagnosis and inappropriate therapy.

The effect of aloe emodin on the proliferation of a new merkel carcinoma cell line

A free-floating cell line has been established from a metastatic lesion of a Merkel cell carcinoma (MCC) patient. The cell line was characterized by immunocytochemical reactions with antibodies against the epithelial and neuroendocrine antigens: cytokeratin 20, neuron-specific enolase, chromogranin A, neurofilament protein, synaptophysin, and calcitonin. Karyotype analysis of the MCC cells showed deletion in chromosomes 3 and 7, loss of chromosome 10, and several translocations in other chromosomes. No mutation was detected in the TP53 gene, after analyzing the complete coding region. Growth factors such as basic fibroblast growth factor, transforming growth factor-beta, and nerve and epidermal growth factors had no effect on the proliferation of the cells. The differentiation-inducing agents sodium butyrate and dimethyl sulfoxide, especially the former, markedly inhibited the proliferation of the MCC cells. Aloe emodin, a natural constituent of aloe vera leaves, significantly inhibited the growth of MCC cells. Aloe emodin has been reported to be nontoxic for normal cells but to possess specific toxicity for neuroectodermal tumor cells. Differentiation-inducing agents, and aloe emodin, merit further investigation as potential agents for treating MCC.

Cutaneous neuroendocrine (Merkel cell) carcinoma occurred after resection of malignant melanoma

An elderly man presented with a brown border nodule of the left upper lip that appeared to be clinically consistent with metastatic melanoma; he had previously undergone two surgical removals of melanoma in the right temporal region. Routine histologic examination was not sufficient for diagnosis, but Merkel cell carcinoma was diagnosed by immunohistochemical studies Neuroendocrine carcinoma of viscera was excluded. Because this case could not be differentiated from amelanotic melanoma and malignant lymphoma based on histologic appearances, immunohistochemical staining was helpful for diagnosis and differentiation.

Second neoplasms in patients with Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) has been associated with a high incidence of other skin tumors and hematological malignancies. The purpose of this study was to analyze data from the Israel Cancer Registry regarding the incidence of second neoplasms in patients with MCC and their impact on survival.

METHODS

Sixty-seven patients in whom MCC was diagnosed between 1983 and 1999 were included. Data were collected on age, gender and ethnic origin, dates of diagnosis of MCC and any other neoplasm, and date and cause of death, if applicable. Comparison of MCC-specific survival, estimated by the Kaplan-Meier product limit method, between patients with no other neoplasm and those with second primary tumors was performed by log rank test. Age-specific standardized incidence ratio (SIR) was calculated using 5751 age- and ethnic-matched malignant melanoma patients as a control group.

RESULTS

Seventeen patients (25%) had a second neoplasm before, concomitant with, or after the diagnosis of MCC; 2 of them also had a third primary tumor. The SIR was 2.8 (95% CI; range, 1.38-4.22), significantly higher than the control group. Almost half the tumors were squamous cell carcinomas, either skin or head and neck, and most of the remainder were hematological malignancies or breast and ovarian adenocarcinomas. On univariate analysis, the presence of another neoplasm, regardless of its chronology, was associated with higher MCC-specific mortality (65% vs. 40% for patients with MCC only; P = 0.022). Analysis of only those patients in whom a second neoplasm developed during follow-up after treatment for MCC yielded an estimated actuarial risk of developing a second primary of 2.1% for each year of observation.

CONCLUSIONS

There is a high incidence of second neoplasms, including noncutaneous solid tumors, in patients with MCC. The presence of these neoplasms, whether they appear before, after, or simultaneously with MCC, is associated with a higher MCC-specific mortality.

Mixed Merkel cell carcinoma and squamous cell carcinoma of the skin

Four mixed Merkel cell and squamous cell carcinomas of the skin are described. The patients ranged in age from 74 to 90 years and demonstrated or had a history of previous ultraviolet or infrared damage to the skin, manifested by basal cell carcinoma, squamous cell carcinoma, actinic keratoses, solar elastosis, and erythema ab igne. Light microscopic examination of all 4 cases revealed invasive neoplasms consisting of 2 distinct but admixed cell types. The predominant cell type was consistent with Merkel cell carcinoma and was characterized by scant cytoplasm, a small dark polygonal nucleus with granular chromatin, a high mitotic rate, and cytokeratin 20 positivity. In each case, the Merkel cell component merged with a cytokeratin 20 negative squamous component characterized by abundant eosinophilic cytoplasm, intercellular bridges, and keratinization with focal squamous pearl formation. Immunohistochemical staining patterns were consistent with the usual pattern for that cell type; transitional cells were not demonstrated. The intimate admixture of the 2 antigenically different neoplastic cell types, and common etiologic role of ultraviolet and possibly infrared damage, lend support to the theory that some Merkel cell carcinomas and squamous cell carcinomas may arise from a pluripotent epidermal stem cell.

Proliferation markers and prognosis in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a frequently aggressive primary cutaneous neuroendocrine malignancy. We investigated 3 cell proliferation markers which may be useful in predicting the aggressiveness of MCC: 1) p53, a tumor suppressor protein, 2) Ki-67, a marker of cell cycling, and 3) proliferating cell nuclear antigen (PCNA). Twenty patients with MCC were studied. The 3 cell proliferation markers were studied by immunoperoxidase. Clinical and immunoperoxidase results were tabulated according to recurrence or death from disease. Of the 20 patients, 10 experienced recurrence, and 10 did not. Seven tumors were positive for p53. We found correlations between recurrence and death in MCC patients, between p53 positivity and recurrence/death, and between p53 positivity and head/neck primary sites. We found no correlation with recurrence by gender or primary site. PCNA was positive in only 1 patient, while Ki-67 was positive in all patients, making these 2 markers unsuitable for predicting recurrence. Further clinical studies will be helpful to confirm and refine the application of this test. Prognostic information from such studies may be useful in planning observation and treatment for patients in the future.

Loss of heterozygosity on the short arm of chromosomes 1 and 3 in sporadic pheochromocytoma and extra-adrenal paraganglioma

Pheochromocytomas and extra-adrenal paragangliomas are tumors of the paraganglia with similar histological characteristics. We examined 12 sporadic pheochromocytomas and 5 extra-adrenal paragangliomas for loss of heterozygosity (LOH) in chromosomes 1p and 3p using a microdissection technique. Chromosomes 1p34-36, 3p21 and the von Hippel-Lindau (VHL) gene locus (3p25) were analyzed. LOH of a selected region on chromosome 1p was detected in 5 of 11 (45%) informative pheochromocytoma cases and in 0 of 5 (0%) informative extra-adrenal paraganglioma cases. LOH of the chromosome 3p25 VHL gene locus was detected in 5 of 9 (45%) informative pheochromocytoma cases and in 0 of 3 (0%) informative extra-adrenal paraganglioma cases. LOH of 3p21 was detected in 2 of 4 (50%) informative extra-adrenal paraganglioma cases. The allelic deletions in chromosomes 1p and 3p appear to be separate events. In conclusion, significant deletions were found at 1p34-36 and 3p25 in sporadic pheochromocytomas but not in extra-adrenal paragangliomas. These findings suggest (1) that multiple genetic factors may be involved in pheochromocytoma tumorigenesis, and (2) extra-adrenal paragangliomas may have a different genetic mechanism of tumorigenesis compared with pheochromocytomas.

Comparative genomic hybridization (CGH) discloses chromosomal and subchromosomal copy number changes in Merkel cell carcinomas

We analyzed three Merkel cell carcinomas (MCC), applying comparative genomic hybridization (CGH) with DNA from paraffin-embedded and cultured tumor material as the probes. By this method, numerous changes in chromosome copy numbers were observed in each tumor investigated. Recurrent gains of chromosomes 1, 6, 18q and 20 were detected in two tumors. A third tumor showed complex chromosomal copy number changes, including gain of chromosome 8 and 9. These gains, as well as gain of chromosome 1 in the first two tumors, were confirmed by fluorescence in situ hybridization to paraffin tissue sections. Our results support the view that important genes for MCC development may be located on chromosomes 1, 6, 18q and 20.

Histopathologic aspects of cutaneous metastatic disease

In cutaneous metastatic disease the histologic pattern may be specific or nonspecific. Carcinoma cutis most often shows only the nonspecific pattern of an adenocarcinoma, a squamous cell carcinoma, or an undifferentiated metastatic tumor. However, certain clinical and histologic characteristics may suggest a primary tumor site and type. In addition, special histologic stains and the use of immunohistochemical and electronmicroscopic techniques may also prove valuable in the diagnosis of carcinoma cutis and other cutaneous metastatic diseases.