Pathologic characterization and differential diagnosis of malignant peritoneal mesothelioma

Extraovarian Primary Peritoneal Carcinomatosis: A Case Report

BACKGROUND Extraovarian primary peritoneal carcinoma (EOPPC) is a rare malignant epithelial tumor with an age-adjusted incidence rate of 6.78 per million, which arises from the peritoneal lining with minimal or no ovarian involvement. EOPPC is a diagnosis of exclusion with the absence of other identifiable primary sites and after surgical assessment and consideration of the histological report to evaluate the extent of ovarian invasion. CASE REPORT A 66-year-old woman complained of mild postprandial epigastric pain. Physical exam revealed positive bowel sounds over all 4 quadrants, with a soft, non-tender abdomen. Distension and dullness to percussion were noted. A CT scan revealed peritoneal fluid, and evaluation of the peritoneal fluid showed an elevated white blood cell count, while fulfilling criteria for exudate. There was no bacterial growth from the peritoneal fluid. Serum tumor markers CEA were significantly elevated, suggestive of an underlying malignancy. An exploratory laparoscopy confirmed diffuse carcinomatosis in the omentum, the coloparietal region bilaterally, as well as surrounding small bowel loops, the transverse and sigmoid colon, and the rectum. A bilateral oophorectomy was performed and 2 biopsies from the thickened peritoneum were taken. The histomorphological features from the pathology examination concluded the patient had peritoneal serous carcinoma with uninvolved ovaries. CONCLUSIONS EOPPC may be misdiagnosed as epithelial ovarian cancer, and should be considered in patients with peritoneal carcinomatosis, normal-sized ovaries, and no identifiable primary lesion. Since the common therapeutic strategies achieve comparable survival rates, failed recognition may be without consequences. However, to further improve survival, optimal cytoreductive surgery is essential and should be made a priority in disease management.

Immunophenotypic and prognostic analysis of PAX8 and TTF-1 expressions in neuroendocrine carcinomas of thymic origin: A comparative study with their pulmonary counterparts

OBJECTIVES

To investigate the immunoreactivity of TTF-1 and PAX8 in neuroendocrine carcinoma of thymic (TNEC) and pulmonary origins (PNEC), and whether their immunophenotyping could be used to distinguish between NEC of the two sites, as well as prognosis of patients with TNEC.

METHODS

Twenty-two cases of TNEC and 20 cases of PNEC were selected for immunohistochemical analysis using PAX8 and TTF-1. Clinical data and follow-up information were obtained for survival analyses.

RESULTS

TTF-1 immunoreactivity was seen in 19 PNEC cases (95%) and 13 TNEC cases (59.1%). PAX8 was negative in all pulmonary tumors while positive in 19 thymic cases (86.4%). TTF-1 positivity was associated with high sensitivity but low specificity for PNEC, and adding PAX8 negativity significantly increased the specificity. PAX8 positivity alone showed essentially 100% specificity and 86.4% sensitivity for TNEC. Survival analysis showed lung metastasis as a significant prognostic factor in TNEC.

CONCLUSION

Our study demonstrated that TTF-1/PAX8 immunophenotyping may be helpful for differential diagnosis of NECs of pulmonary and thymic origins. TTF-1+/PAX8- immunophenotyping showed high specificity for PNECs, while PAX8+ alone showed a good diagnostic accuracy for TNEC. Lung metastasis was a predictive factor that associated with survival of TNEC patients. J. Surg. Oncol. 2016;114:697-702. © 2016 Wiley Periodicals, Inc.

Malignant mesothelioma: facts, myths, and hypotheses

Malignant mesothelioma (MM) is a neoplasm arising from mesothelial cells lining the pleural, peritoneal, and pericardial cavities. Over 20 million people in the US are at risk of developing MM due to asbestos exposure. MM mortality rates are estimated to increase by 5-10% per year in most industrialized countries until about 2020. The incidence of MM in men has continued to rise during the past 50 years, while the incidence in women appears largely unchanged. It is estimated that about 50-80% of pleural MM in men and 20-30% in women developed in individuals whose history indicates asbestos exposure(s) above that expected from most background settings. While rare for women, about 30% of peritoneal mesothelioma in men has been associated with exposure to asbestos. Erionite is a potent carcinogenic mineral fiber capable of causing both pleural and peritoneal MM. Since erionite is considerably less widespread than asbestos, the number of MM cases associated with erionite exposure is smaller. Asbestos induces DNA alterations mostly by inducing mesothelial cells and reactive macrophages to secrete mutagenic oxygen and nitrogen species. In addition, asbestos carcinogenesis is linked to the chronic inflammatory process caused by the deposition of a sufficient number of asbestos fibers and the consequent release of pro-inflammatory molecules, especially HMGB-1, the master switch that starts the inflammatory process, and TNF-alpha by macrophages and mesothelial cells. Genetic predisposition, radiation exposure and viral infection are co-factors that can alone or together with asbestos and erionite cause MM. J. Cell. Physiol. 227: 44-58, 2012. © 2011 Wiley Periodicals, Inc.