INCIDENCE AND LOCATION:
The diagnosis and treatment of malignant mesothelioma is a particular challenge. In very rare tumor diseases such as mesothelioma, the diagnosis as well as the treatment in specialized centers with corresponding experience must be striven for.
The prognosis for a patient with a malignant mesothelioma is bad in spite of new treatment approaches, the survival time is on the average one to one and a half a year, the 5 year survival rate is below 20%. Frequently, a malignant mesothelioma is recognized only in an advanced stage, so that in the case of diagnosis, a curative therapy approach is often no longer possible.
THE FOLLOWING PROGNOSTIC FACTORS WERE DESCRIBED:
The tumor stage at the time of diagnosis
The general state (performance index according to Karnofsky)
The histological tumor subtype
The lymph node status
Thus, patients with a malignant epithelial mesothelioma usually have a longer survival probability than patients with malignant biphasic or sarcomatoid mesothelioma.
The symptoms of malignant mesothelioma disease are dependent on the primary localization of the tumor.
Malignant pleural mesotheliomas are characterized by thoracic pain, dyspnoea, and possibly a coughing symptom. A pleural effusion is usually present. In rare cases pneumothorax is the first symptom.
In patients with malignant peritoneal mesotheliomas, ascites is often observed. There are abdominal complaints in the form of nonspecific pain, pressure, and altered bowel activity.
In rare malignant pericardial mesothelioma, pain occurs behind the sternum, cardiac arrhythmia, and heart palpation.
In malignant mesotheliomas of the tunica vaginalis testis, recurrent hydroceles (accumulations of serous fluid) are observed.
In addition to the symptoms mentioned, symptoms such as weight loss, performance impairment, fever and night sweats can occur, as with all tumor diseases.
In advanced stages, a lymphogenic or systemic metastasis may occur.
The diagnosis of mesothelioma is among the most difficult questions within the pathology. The German Mesothelioma Registry is available as a reference center for the histological diagnosis and / or for a second assessment of the tissue sample.
Malignant mesotheliomas show a very varied, fine-tissue image with a variety of papillary, tubular, adenomatoid, azinic, small-cell, spindle-cell, lymphohistiocytoids, deciduoid, clear-cell, ring-ring-cell or adenoid-cystic differentiations. The majority of the tumors contain combinations of the different patterns of differentiation. According to the WHO classification of 2004, epitheloids, biphasic, desmoplastic and sarcomatoid subtypes are distinguished.
Because of this variant-rich fine-web image – even within the smallest tumor biopsies – a large number of possible differential diagnoses arise during diagnostics. The demarcation of still benign changes occurs with the view that, if necessary, only biopsies of a few millimeters size are present, The very heterogeneous differentiation patterns of the malignant mesothelioma and the large number of tumors that can be metastasized or adjacent to the pleura are the reasons for the difficulties of mesothelioma diagnostics. Macroscopically, a pleural carcinoma is not distinguished from a malignant mesothelioma. A significantly increased error probability (false-positive and false-negative) must be expected.
Immunohistochemical investigations are a standard procedure in the differential diagnosis of a mesothelioma against the metastatic withdrawal of another primary tumor.
There is no single specific marker. Different marker panels must be used depending on the tumor type and the differential diagnosis. The following markers have proved to be particularly suitable for the diagnosis of mesotheliomas:
calretinin (positive marker), MOC31 (negative marker), BerEP4 (negative marker), D2-40 (positive marker), TTF-1 (negative marker), cytokeratins Positive markers) and WT-1 (positive marker).
MOLECULAR PATHOLOGICAL STUDIES:
Molecular pathological analyzes can also help in distinguishing malignant mesotheliomas from reactive changes, precursor lesions, pleural carcinomas or sarcomas. Thus, almost all malignant sarcomatoid mesotheliomas of the pleura have a p16 deletion. In the case of malignant epithelial pleural mesotheliomas, however, the deletion rate is only between 60 and 80% and for the peritoneal mesotheliomas, this deletion is even less frequent with less than 40%.
HIGHLY DIFFERENTIATED PAPILLARY MESOTHELIOMAS (WDPM):
An exception among the mesotheliomas are the well-differentiated papillary mesotheliomas (WDPM). These usually benign lesions are found as random findings in the case of an abdominal surgery of other indications, especially in (young) women. Since the WDPM only grows very slowly, usually occurs singularly, is very small and also does not form metastases and is not invasive, it can be completely removed and the prognosis for the patient is usually very favorable.