TMEM16A alternative splicing coordination in breast cancer.

BACKGROUND: TMEM16A, also known as Anoctamin-1, is a calcium-activated chloride channel gene overexpressed in many tumors. The role of TMEM16A in cancer is not completely understood and no data are available regarding the potential tumorigenic properties of the multiple isoforms generated by alternative splicing (AS). METHODS: We evaluated TMEM16A AS pattern, isoforms distribution and Splicing Coordination (SC), in normal tissues and breast cancers, through a semi-quantitative PCR-assay that amplifies transcripts across three AS exons, 6b, 13 and 15. RESULTS: In breast cancer, we did not observe an association either to AS of individual exons or to specific TMEM16A isoforms, and induced expression of the most common isoforms present in tumors in the HEK293 Flp-In Tet-ON system had no effect on cellular proliferation and migration. The analysis of splicing coordination, a mechanism that regulates AS of distant exons, showed a preferential association of exon 6b and 15 in several normal tissues and tumors: isoforms that predominantly include exon 6b tend to exclude exon 15 and vice versa. Interestingly, we found an increase in SC in breast tumors compared to matched normal tissues. CONCLUSIONS: As the different TMEM16A isoforms do not affect proliferation or migration and do not associate with tumors, our results suggest that the resulting channel activities are not directly involved in cell growth and motility. Conversely, the observed increase in SC in breast tumors suggests that the maintenance of the regulatory mechanism that coordinates distant alternative spliced exons in multiple genes other than TMEM16A is necessary for cancer cell viability.

Plasma cell myeloma presenting with diffuse pleural involvement: a hitherto unreported pattern of a new mesothelioma mimicker.

We described 2 cases of plasmacytoma presenting with a preponderant involvement of the pleural membranes simulating clinically, radiologically, and on gross pathologic inspection a primary mesothelioma. The patients were an 80-year-old man and a 45-year-old woman. In both cases, the clinical presentation was that of a serosal tumor, including effusions and pleural thickening. In the former, the serosal infiltration raised the suspicion of mesothelioma reinforced by history of occupational exposure to asbestos. Patient general condition deteriorated rapidly. Postmortem examination revealed unilateral encasing of the lung within a thick, irregular neoplastic rind. In addition, tumoral involvement was seen in the homolateral third rib and the clavicle. Histologic examination of pleural masses demonstrated diffuse infiltration by highly atypical, pleomorphic plasma cells with kappa chain restriction. In the second case, clinical presentation was also suspicious of mesothelioma. Nonetheless, a pleural biopsy specimen showed irregular sheets of plasma cells showing kappa light chain restriction. A bone marrow aspirate was also positive for abnormal plasma cell infiltrates. Despite chemotherapy, the patient died 4 months after presentation. Although rarely, it seems that plasmacytoma may present with an exclusive or preponderant pleural involvement; and it may therefore be added to the list of pseudomesotheliomatous tumors.

A tumor with composite pilo-folliculosebaceous differentiation harboring a recently described new entity--melanocytic matricoma.

We report on a case of a peculiar tumor of the pilosebaceous unit showing a composite histologic appearance. The case presented as a pigmented crusted lesion on the back of the nose of a 62-year-old woman with markedly sun-damaged skin. Histologically, the superficial portion of the neoplasm was composed of buds and nests of basaloid epithelium with varying degrees of pilar and sebaceous differentiation. Adjacent to this component, lobules of squamous cells with cytoplasmic glycogenation suggesting the mature outer root sheath were seen. In the underlying dermis, there was a well-defined nodular proliferation composed of variably pigmented basaloid matrical cells forming clusters of "shadow" or "ghost cells" admixed with numerous melanized dendritic melanocytes; this last component of the neoplasm was identical to a recently described entity, melanocytic matricoma. The small size, circumscription, and absence of necrosis favored benignity, although the cytologic atypia of matrical cells did not exclude malignancy. The case is interesting not only because it is the third reported case of a peculiar neoplasm imitating the epithelial-melanocytic interaction in the embryonal hair follicle or bulb of the anagen follicle but because the part resembling melanocytic matricoma presented as a component of a complex lesion. We believe that sunlight may have played a role in the development of this peculiar neoplasm.