Merkel cell carcinoma and multiple Bowen's disease: incidental association or possible relationship to inorganic arsenic exposure?

A cornucopia of human polyomaviruses

During the past 6 years, focused virus hunting has led to the discovery of nine new human polyomaviruses, including Merkel cell polyomavirus, which has been linked to Merkel cell carcinoma, a lethal skin cell cancer. The discovery of so many new and highly divergent human polyomaviruses raises key questions regarding their evolution, tropism, latency, reactivation, immune evasion and contribution to disease. This Review describes the similarities and differences among the new human polyomaviruses and discusses how these viruses might interact with their human host.

Pathological, immunological and biochemical markers of subchronic arsenic toxicity in rats

Subchronic exposure to arsenic in rats was investigated to identify sensitive indicators of subclinical toxicity in rats. Immunological, pathological, and biochemical bioindicators were examined in rats exposed to arsenic in their drinking water. Juvenile male Wistar rats were allocated to four treatment groups receiving 0, 0.4, 4, and 40 ppm of arsenite in drinking water for 18 wks. Besides daily monitoring for clinical signs of adverse health effects, clinical biochemistry, B-cell-mediated and innate immune responses, plus gross, and histopathology were examined. In vitro tests of oxidative damage to basic cellular constituents, lipids, proteins, and nucleic acids, were measured using thiobarbituric acid reacting substances (TBARS) assays, protein carbonyl formation, and 8-hydroxydeoxyguanosine (8-OHdG), respectively. Clinical changes in the rats were limited to decreased feed and water intake in the high- (40 ppm) dose group (P < 0.05), however, growth rate was not affected. Serum biochemical changes occurred in blood urea nitrogen, K(+) , Cl(-) , and alanine aminotransferase (ALT) from arsenic exposure. Immunotoxicity was evident through a dose-dependent suppression of the secondary antibody-mediated response to a T-cell-dependent antigen, keyhole limpet hemocyanin (KLH). Histopathology of the liver revealed marked fatty infiltration and vacuolization particularly evident in periacinar hepatocytes. This pattern of toxicopathology in the high-exposure group may be related to the significantly higher (P < 0.05) oxidative stress, demonstrated through lipid peroxidation (TBARS assay) in the rats exposed to 40 ppm arsenite. The present study revealed that young, growing rats exposed to arsenic for 18 wks tolerated exposures up to 4 ppm. At higher doses, there was evidence of hepatotoxicity, humoral immunity was compromised, and an adverse effect on hepatic organelle and cell membranes was evident through a dose dependent increased in oxidative stress.

Soft Tissue Tumors of the Hand. 2. Malignant

Soft tissue tumors of the hand arise from skin, subcutaneous tissue, tendons, nerve, and blood vessels. Many of these lesions occur on other parts of the body; however, the hand remains a unique site because these tumors have symptoms, appearances, treatments, and prognoses that may be quite different than when on other parts of the body. Their characteristics and the severity of symptoms vary markedly depending on the exact location, size, and type of tumor-and many of these tumors can have multiple forms of presentation. Two articles are intended to provide an overview of benign (previous article) and malignant tumors (this article) of the hand. The rarer and more deleterious tumors are discussed in detail while the common tumors and epidermal lesions with which practitioners are familiar are briefly overviewed. At the completion of these review articles, participants should be able to identify and diagnose various benign and malignant hand tumors as well as understand the accepted current treatment of these growths.

Merkel cell carcinoma in patients with long-term ingestion of arsenic

Merkel cell carcinoma (MCC) is a rare primary neuroendocrine carcinoma of the skin, mostly occurring late in life on sun-exposed body parts. Little is known about the specific etiological factors in the pathogenesis of MCC. A previous report indicated that arsenic exposure might cause MCC, which might be another specific type of skin cancer associated with arsenic exposure. On the southwest coast of Taiwan, high arsenic levels in artesian well water have been documented, and various diseases associated with arsenic exposure have been found to be prevalent in this area. We report two pathologically confirmed cases of MCC in patients who had histories of long-term ingestion of arsenic from drinking water. The tumors were on the anterior chest wall, an area less exposed to the sun, in both cases. The literature on the dose-response relationship between arsenic exposure and MCC is limited. We estimated that the total arsenic ingested by these two cases was around 14.7 and 2.6 gm, respectively. We also tried to assess the cancer risk on the basis of the estimated doses of arsenic exposure and the cancer risk model developed by the U.S. Environmental Protection Agency (EPA). The estimated lifetime target cancer risk was 1.3 x 10(-2) in Case 1 and 2.3 x 10(-3) in Case 2. Both are much higher than the 10(-6) upper limit on lifetime cancer risk put forth by the U.S. EPA health protection standard. We believe that arsenic intoxication played an important role in the carcinogenic process of MCC in our cases.

Epidemiology of primary Merkel cell carcinoma in the United States

BACKGROUND

Merkel cell carcinoma (MCC) is a rare, aggressive skin cancer.

OBJECTIVE

We sought to describe primary MCC incidence trends, epidemiology, and predictors of survival.

METHODS

The population covered by the Surveillance, Epidemiology, and End Results Program was analyzed as a prospective cohort. We measured age-adjusted incidence rates (per 100,000 person-years) and effect of age, anatomic site, and stage on survival.

RESULTS

Incidence was higher in males (0.34) than in females (0.17). Cases (n = 1034) occurred mostly in whites (94%), in people older than 65 years (76%), and at the head (48%). The 5-year relative survival was 75%, 59%, and 25% for localized, regional, and distant MCC, respectively. Female sex, limb presentation, localized disease, and younger age were positive predictors of survival.

CONCLUSION

The highest incidence of MCC was observed in whites, males, and in people older than 65 years. Only 49% of cases were reported as localized. Better survival was associated with limb localization, early-stage disease, younger age, and female sex.

Effects of arsenic on human keratinocytes: morphological, physiological, and precursor incorporation studies

Measurement of in vitro percutaneous absorption of As(III) and As(V) by artificial human skin shows a strong affinity of arsenic for the human keratinocytes, with 1-10% of the applied arsenic dose retained by the artificial skin per hour. The inordinate retention of arsenic by the skin is a risk factor for As toxicity. The calculated permeability constant (K(p)) averaged about 4.3 x 10(-5) cm/h for As(V) and 10.1 x 10(-5) cm/h for As(III). A facile calculation suggests that dermal absorption during showering and hand washing can be an important exposure route if the water contains more than 100 microg/L As(III) or As(V). The effects of the absorbed arsenic in artificial skin were evaluated in terms of morphological characteristics, integrity of the cell membrane (by means of lactate dehydrogenase and MTS assays), and rates of DNA, RNA, and protein synthesis estimated by incorporation of radioactive precursors. We found significant morphological changes, cytotoxicity associated with disruption of the cell membrane, and inhibition of DNA and protein syntheses at As(III) exposure doses as low as 10 microg/L.

Merkel cell carcinoma: report of 10 cases and review of the literature

BACKGROUND

Merkel cell carcinoma (MCC) is a rare primary neuroendocrine skin tumor that usually arises in the head and neck or the extremities of elderly patients. Because of the limitation of retrospective data, optimal treatment is not well defined.

OBJECTIVE

Our purpose was to present the clinical course and treatment of 10 patients with MCC and review the published literature on MCC.

METHOD

We conducted a retrospective analysis and obtained detailed clinical information for all 10 patients treated for MCC at our institution from 1986 through 1998. The medical literature was also reviewed for natural history and treatment recommendations using MEDLINE search.

RESULTS

Five men and 5 women received their treatment between 1986 and 1998 for MCC (5 had stage IA disease, 4 stage IB, 1 stage II). The mean age was 70.3 years (range, 47-86 years). Seven tumors were located on the head and neck and 3 on extremities. Five of 10 patients had a relapse (mean time before recurrence, 5.7 months) (range, 2 weeks-20 months); one patient had local recurrence, one had regional lymph node recurrence, and 3 had both local and regional lymph node recurrence. In 4 patients systemic metastases developed. Long survival is also noted (6 to > 164 months); 4 patients died of MCC. After initial surgery, 9 patients received radiotherapy at some point and 3 patients also received chemotherapy. Five of 10 patients had 13 previously treated or coexisting malignant neoplasms. In one patient MCC developed in a previously irradiated field. Review of 875 cases showed a male/female ratio of 1.5:1; location of tumors was as follows: head and neck, 47%; extremities, 40%; trunk, 8%; unknown primary site, 5%. Local recurrence was observed in 25%, regional lymph node involvement in 52%, distant metastasis in 34%, and MCC was a cause of death in 34%.

CONCLUSION

MCC has a high incidence of locoregional recurrence with distant metastases that is more common with higher stage lesions. Early local management of smaller lesions results in good long-term survival. It is not known whether prophylactic lymph node dissection and/or radiation and adjuvant radiation increases survival. Long survival can be achieved after treating locoregional recurrence. The role of chemotherapy is still controversial and should be considered in patients with advanced disease and those not thought to be candidates for surgery.

Merkel cell carcinoma: report of three cases

Three cases of Merkel cell carcinoma are reported: Case 1 on the upper eyelid with regional lymph node metastasis, Case 2 with spontaneous regression after repeated biopsies, and Case 3 presumably developing on the lesion of pre-existing Bowen's disease. In Case 2, the biopsy specimen was characterized by numerous apoptotic cells in the periphery of the tumor nests surrounded by lymphocytic infiltration. In Case 3, the tumor developed after injury to the pre-existing lesion of Bowen's disease.