Sarcomatoid mesothelioma: a clinical–pathologic correlation of 326 cases

Abstract

Sarcomatoid mesothelioma is the least common, but most aggressive of the three major histological types of mesotheliomas. This study comprises 326 cases of sarcomatoid mesotheliomas among 2000 consecutive malignant mesothelioma cases received in consultation (16%). Patients included 312 men (96%) and 14 women (4%), with a median age of 70 years (range 41-94 years). Most tumors were pleural (319; 98%), and 7 were peritoneal (2%). Some desmoplastic features were identified in 110 cases (34%), and 70 (21%) were classified as desmoplastic. Rare subtypes included two cases with a lymphohistiocytoid pattern (o1%) and eight heterologous mesotheliomas (2%). Labeling for cytokeratins (CKs) was observed in 261/280 cases (93%), and for calretinin and vimentin in 31 and 91%, respectively. Pleural plaques were present in 79% of cases for which information was available, and asbestosis was diagnosed in 34/127 cases (27%). Median survival was 3.5 months. Fiber analysis was performed in 61 cases. The median asbestos body count was 1640/g wet lung tissue (by light microscopy). Amosite fibers were the most commonly identified fibers using energy-dispersive X-ray analysis and were significantly higher in the sarcomatoid cases, as were uncoated fibers using scanning electron microscopy. This study represents the largest series of sarcomatoid and desmoplastic malignant mesotheliomas to date and confirms the diagnostic usefulness of CK immunohistochemistry. The relationship with asbestos exposure-particularly amosite-and an association with pleural plaques and less often asbestosis is confirmed.

BAP1 (BRCA1-associated protein 1) is a highly specific marker for differentiating mesothelioma from reactive mesothelial proliferations

“…It is known that epithelioid and sarcomatoid mesotheliomas show different antigen expression, with many mesothelial markers being frequently negative in sarcomatoid subtype. [67][68][69][70][71][72][73] A recent gene expression profile analysis applied to a large series of pleural mesothelioma cell lines and tissue samples identified two mesothelioma subgroups. Although sarcomatoid and desmoplastic mesotheliomas belonged to a single group associated with poorer prognosis, epithelioid mesotheliomas were either included in the sarcomatoid/desmoplastic group or fell in a distinct subgroup with a better prognosis.…”

Guidelines for Pathologic Diagnosis of Malignant Mesothelioma: 2012 Update of the Consensus Statement from the International Mesothelioma Interest Group

“…74,75 False positives can occur by the misinterpretation of positive D2-40 reactivity within benign entrapped lymphatics or reactive mesothelial elements. A recent study 61 reported the presence of usually focal calretinin immunoreactivity labeling fewer than 10% of tumor cells in 31% of sarcomatoid mesotheliomas.…”

Malignant (Diffuse) Mesothelioma in Patients With Hematologic Malignancies: A Clinicopathologic Study of 45 Cases

“…However, when we controlled for histologic type, the survival difference was no longer significant (Figure 2, B). This is likely due to the known poor survival in sarcomatoid mesotheliomas, 44 which were more common in the nonirradiated group. Nonetheless, there was still a trend toward longer survival in the postradiation group, and the lack of statistical significance may have been due to the few cases.…”