Correlative polarizing light and scanning electron microscopy for the assessment of talc in pelvic region lymph nodes

Talc and human cancer: a systematic review of the experimental animal and mechanistic evidence

The potential carcinogenicity of talc has been evaluated in many studies in humans and experimental animals published in the scientific literature over the last several decades, with a number of these studies reporting no associations between talc exposure and any type of cancer. In order to fully understand the current state of the science regarding the potential for talc to induce human cancers, we conducted a comprehensive and systematic review of the available experimental animal and mechanistic evidence (in conjunction with a systematic review of the epidemiology evidence in a companion analysis) to evaluate whether it supports talc as being carcinogenic to humans. We considered study quality and its impact on the interpretation of results and evaluated all types of cancer and all exposure routes. We also evaluated the evidence on the potential for talc to migrate in the body to potential tumor sites. We identified seven experimental animal carcinogenicity studies and 11 mechanistic studies of talc to systematically review. We found that several of the experimental animal carcinogenicity studies of talc have limitations that preclude their sensitivity to detect increases in tumor incidence. Regardless, the studies cover multiple exposure routes, species, and exposure durations, and none indicate that talc is a carcinogen in experimental animals except in rats under conditions of extremely high exposure that likely resulted in lung particle overload, a nonspecific effect of high exposures to poorly soluble particles, and not from any carcinogenic properties of talc. Lung particle overload leading to lung tumor formation has only been observed in rats and not in any other species, including humans. The mechanistic studies indicate that talc is not genotoxic or mutagenic, but can induce some effects that could be events on a possible pathway to carcinogenicity, mainly at high exposures or in in vitro studies with exposures of unclear relevance in vivo, but these effects are not consistent across studies and cell types. This systematic review of the experimental animal carcinogenicity and mechanistic evidence for talc indicates that an association between talc exposure and cancer is not expected in humans. Talc carcinogenicity is not plausible in any species except rats, and only when the exposure conditions are high enough to induce lung particle overload, which is not relevant to human exposures.

Systematic review of the association between talc and female reproductive tract cancers

Talc is a hydrous magnesium sheet silicate used in cosmetic powders, ceramics, paints, rubber, and many other products. We conducted a systematic review of the potential carcinogenicity of genitally applied talc in humans. Our systematic review methods adhere to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and incorporated aspects from the US Institute of Medicine (IOM, now the National Academy of Medicine) and several US EPA frameworks for systematic reviews, evaluating and integrating the epidemiological, animal, and mechanistic literature on talc and cancer. We conducted a comprehensive literature search. Detailed data abstraction and study quality evaluation, adapting the Toxic Substances Control Act (TSCA) framework, were central to our analysis. The literature search and selection process identified 40 primary studies that assessed exposure to talc and female reproductive cancer risks in humans (n = 36) and animals (n = 4). The results of our evaluation emphasize the importance of considering biological plausibility and study quality in systematic review. Integrating all streams of evidence according to the IOM framework yielded classifications of suggestive evidence of no association between perineal application of talcum powders and risk of ovarian cancer at human-relevant exposure levels. We also concluded that there is suggestive evidence of no association between genital talc application and endometrial cancer, and insufficient evidence to determine whether a causal association exists between genital talc application and cervical cancer based on a smaller but largely null body of literature.

Primary Ovarian Mesothelioma: A Case Series with Electron Microscopy Examination and Review of the Literature

Primary ovarian mesothelioma is a rare, aggressive neoplastic disease with a poor prognosis. At onset, the tumor is only rarely limited to the ovaries and usually already widespread in the peritoneum. The rarity of this entity and the difficulties differentiating it from either ovarian carcinoma or peritoneal mesothelioma may lead to frequent misdiagnoses and may raise some concerns about its histogenesis. Thus, reporting such rare cases is fundamental to gain greater awareness of this neoplasm and try to answer unsolved questions. Herein, we described four cases of histological diagnoses of ovarian mesothelioma extrapolated by the regional mesothelioma register of Apulia (southern Italy). In all cases, a detailed medical history was collected according to national mesothelioma register guidelines. A broad panel of antibodies was used for immunohistochemistry to confirm the diagnoses. Moreover, ovarian tissue samples were also examined by transmission and scanning electron microscopy, detecting asbestos fibers and talc crystals in two cases. Because of the few cases described, we reviewed the English literature in the Medline database, focusing on articles about ovarian mesothelioma "misclassification", "misdiagnosis", "diagnostic challenge" or "diagnostic pitfall" and on unsolved questions about its histogenesis and possible risk factors.

Analytic comparison of talc in commercially available baby powder and in pelvic tissues resected from ovarian carcinoma patients

OBJECTIVE

Measure the size and shape of talc particles in talcum powder and compare this data to the size and shape of talc particles found in surgically resected tissues from patients with ovarian carcinoma.

METHODS

Using polarized light microscopy (PLM) and scanning electron microscopy (SEM), we measured the size and shape of talc particles in samples of talc-containing baby powder (TCBP) and surgically resected pelvic tissues (hysterectomies) from talc-exposed patients with ovarian carcinoma.

RESULTS

The most frequent class of particles in TCBP can be unequivocally identified as talc, using both polarized light microscopy and scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX). The talc particles found in resected tissues from ovarian carcinoma patients are similar in size and shape to the most abundant morphological class of particles in TCBP.

CONCLUSIONS

This finding, combined with previous epidemiological literature and tissue-based analytical studies, provides further evidence that the small, isodiametric particles that dominate TCBP can migrate from the perineum and become lodged in distal structures in the female reproductive tract, where they may lead to an increased risk of developing ovarian carcinoma.

A critical review of talc and ovarian cancer

The association between perineal talc use and ovarian cancer has been evaluated in several epidemiology studies. Some case-control studies reported weak positive associations, while other case-control and three large prospective cohort investigations found this association to be null. A weight-of-evidence evaluation was conducted of the epidemiology, toxicity, exposure, transport, in vitro, and mechanistic evidence to determine whether, collectively, these data support a causal association. Our review of the literature indicated that, while both case-control and cohort studies may be impacted by bias, the possibility of recall and other biases from the low participation rates and retrospective self-reporting of talc exposure cannot be ruled out for any of the case-control studies. The hypothesis that talc exposure induces ovarian cancer is only supported if one discounts the null results of the cohort studies and the fact that significant bias and/or confounding are likely reasons for the associations reported in some case-control investigations. In addition, one would need to ignore the evidence from animal experiments that show no marked association with cancer, in vitro and genotoxicity studies that did not indicate a carcinogenic mechanism of action for talc, and mechanistic and transport investigations that did not support the retrograde transport of talc to the ovaries. An alternative hypothesis that talc does not produce ovarian cancer, and that bias and confounding contribute the reported positive associations in case-control studies, is better supported by the evidence across all scientific disciplines. It is concluded that the evidence does not support a causal association between perineal talc use and ovarian cancer.

Analysis of particles from hamster lungs following pulmonary talc exposures: implications for pathogenicity

BACKGROUND

Talc, a hydrous magnesium silicate, often used for genital hygiene purposes, is associated with ovarian carcinoma in case-control studies. Its potential to cause inflammation, injury, and functional changes in cells has been described. A complication of such studies is that talc preparations may be contaminated with other materials. A previous study by (Beck et al. Toxicol Appl Pharmacol 87:222-34, 1987) used a hamster model to study talc and granite dust exposure effects on various biochemical and cellular inflammatory markers. Our current study accessed key materials used in that 1987 study; we re-analyzed the original talc dust with contemporary scanning electron microscopy and energy dispersive x-ray analysis (SEM/EDX) for contaminants. We also examined the original bronchoalveolar lavage (BAL) cells with polarized light microscopy to quantify cell-associated birefringent particles to gain insight into the talc used.

RESULTS

SEM/EDX analyses showed that asbestos fibers, quartz, and toxic metal particulates were below the limits of detection in the original talc powder. However, fibers with aspect ratios ≥3:1 accounted for 22% of instilled material, mostly as fibrous talc. Talc (based on Mg/Si atomic weight % ratio) was the most abundant chemical signature, and magnesium silicates with various other elements made up the remainder. BAL cell counts confirmed the presence of acute inflammation, which followed intratracheal instillation. Measurements of cell associated birefringent particles phagocytosis revealed significant differences among talc, granite, and control exposures with high initial uptake of talc compared to granite, but over the 14-day experiment, talc phagocytosis by lavaged cells was significantly less than that of granite. Phagocytosis of talc fibers by macrophages was observed, and birefringent particles were found in macrophages, neutrophils, and multinucleate giant cells in lavaged cells from talc-exposed animals.

CONCLUSION

Our data support the contention that talc, even without asbestos and other known toxic contaminants, may elicit inflammation and contribute to lung disease. Our findings support the conclusions of (Beck et al. Toxicol Appl Pharmacol 87:222-34, 1987) study. By analyzing particulate exposures with polarized light microscopy and SEM/EDX, fibrous talc was identified and a distinctive pattern of impaired particulate ingestion was demonstrated.

The effect of talc particles on phagocytes in co-culture with ovarian cancer cells

Talc and titanium dioxide are naturally occurring water-insoluble mined products usually available in the form of particulate matter. This study was prompted by epidemiological observations suggesting that perineal use of talc powder is associated with increased risk of ovarian cancer, particularly in a milieu with higher estrogen. We aimed to test the effects of talc vs. control particles on the ability of prototypical macrophage cell lines to curb the growth of ovarian cancer cells in culture in the presence of estrogen. We found that murine ovarian surface epithelial cells (MOSEC), a prototype of certain forms of ovarian cancer, were present in larger numbers after co-culture with macrophages treated to a combination of talc and estradiol than to either agent alone or vehicle. Control particles (titanium dioxide, concentrated urban air particulates or diesel exhaust particles) did not have this effect. Co-exposure of macrophages to talc and estradiol has led to increased production of reactive oxygen species and changes in expression of macrophage genes pertinent in cancer development and immunosurveillance. These findings suggest that in vitro exposure to talc, particularly in a high-estrogen environment, may compromise immunosurveillance functions of macrophages and prompt further studies to elucidate this mechanism.

Migration of Talc From the Perineum to Multiple Pelvic Organ Sites

OBJECTIVES

Genital talc use is associated with increased risk for ovarian carcinoma in epidemiologic studies. Finding talc in pelvic tissues in women with ovarian carcinoma who have used talc is important in documenting exposure and assessing talc's biologic potential, but tissue-based morphology studies have been rarely reported.

METHODS

We report five patient cases with documented perineal talc use, each of whom had talc (by both polarized light and scanning electron microscopy) in multiple pelvic sites distant from the perineum. Six negative-exposure control patients were also analyzed.

RESULTS

Talc particles were found in exposed patients, typically within two or more of the following locations: pelvic region lymph nodes, cervix, uterine corpus, fallopian tubes, and ovaries.

CONCLUSIONS

Our report adds new insights into the biologic potential of talc and suggests additional anatomic sites that should be closely examined for talc by oncologic surgical pathologists in the setting of perineal talc use.