L1CAM expression in cystic mesothelial lesions: a comparison with adenomatoid tumours, well-differentiated papillary mesothelial tumours and malignant mesotheliomas

New developments in mesothelial pathology

This review article examines some new and some problem areas in mesothelial pathology, four of which are discussed, as follows. (1) The concept of mesothelioma in situ: this lesion is defined as a single layer of bland mesothelial cells without evidence of invasion, but that have lost BAP1 and/or MTAP by immunohistochemistry. Benign reactions can exactly mimic mesothelioma in situ, but a hint to the correct diagnosis is a story of recurrent pleural effusions/ascites of unknown aetiology without radiological or direct visual evidence of tumour. (2) The nature of well-differentiated papillary mesothelial tumour (WDPMT): WDPMT has a long history of arguments regarding its behaviour, and this uncertainty can now be seen to arise, in part, from the observation that some forms of mesothelioma in situ microscopically look exactly like WDPMT. Hence, it is recommended to always run at least a BAP1 stain on any lesion that looks like WDPMT. Both flat and WDPMT-like mesothelioma in situ are strongly associated with eventual development of invasive mesothelioma, but this process is relatively slow. (3) New immunostains for separating mesothelioma from other tumours: here, it is proposed that in most cases, and particularly when the differential is epithelioid mesothelioma versus non-small cell lung cancer, one can make this separation with extremely high sensitivity and specificity using just two stains: HEG1 and claudin-4. (4) Markers for separating benign from malignant mesothelial proliferations: this topic is briefly reviewed, with an indication of which markers are generally accepted and the best utilisation and possible limitations of each marker.

Peritoneal Mesothelioma-An Update

A remarkable amount of new information has been generated on peritoneal mesothelioma (PeM), ranging from nomenclature changes, including the removal of "malignant" when referring to this neoplasm and the use of the term "tumor" rather than "mesothelioma" to designate the neoplasm formerly known as "well-differentiated papillary mesothelioma", to the acknowledgment that PeMs can be associated with tumor predisposition syndromes or germline mutations. Although the disease is still more frequently seen in caucasian males, PeM is not uncommon in women. In addition, it can represent a diagnostic challenge when it has an uncommon presentation (ie, paraneoplastic syndrome or incidental finding) or when it has confounding histologic features. Ancillary testing, including immunohistochemical stains, in situ hybridization for CDKN2A or NF2 , and molecular studies, in selected cases, allows its correct diagnosis. The molecular landscape of PeM is still a work in progress; however, some findings, such as ALK gene rearrangements and EWSR1/FUS-ATF1 fusions, are specifically seen in PeM of young patients. The biological behavior of PeM is variable; however, cytoreductive surgery and hyperthermic intraperitoneal chemotherapy have markedly improved the survival of patients affected by this disease.

Immunohistochemical analysis of L1 cell adhesion molecule and high endothelial venules in breast cancer brain metastasis

BACKGROUND

The vasculature is a crucial factor in tumor development. Vascular co-option achieved by the L1 cell adhesion molecule (L1CAM) and lymphocyte recruitment inside tumors by high endothelial venules (HEVs) are important prognostic factors in primary breast cancer. Their status in breast cancer brain metastasis is unknown.

AIM OF THE STUDY

To explore the status of L1CAMs and HEVs in this tumor compartment.

MATERIAL AND METHODS

Thirty resected breast cancer brain metastases were immunohistochemically studied for L1CAM and MECA-79, an HEV marker. Clinicopathological factors were recorded.

RESULTS

Age at brain metastasis diagnosis ranged from 37 to 80 years (median 55). The time to brain metastasis development after primary tumor diagnosis ranged from 12 to 187 months (median 57). Median overall survival after brain metastasis diagnosis was 29 months. None of the tumors expressed the factors studied.

CONCLUSION

L1CAM and high endothelial venules are not found in breast cancer brain metastasis.