Primary tumors of the pleura can be categorized as diffuse or localized:
Diffuse malignant mesothelioma is more common,
is related to asbestos exposure,
and is associated with a poor prognosis.
Localized mesothelioma is called localized fibrous tumor of pleura (LFTP); this tumor is an uncommon neoplasm (accounting for less than 5% of all pleural tumors),
has a controversial histogenesis and is unrelated to asbestos exposure.
LFTPs exist in benign and malignant forms
Nowadays,
the origin is recognized widely as mesenchymal cells of submesothelial tissues of the pleura rather than mesothelial cells .
LOCALIZED FIBROUS TUMOR OF THE PLEURA (LFTP):
Synonyms:
Fibrous mesothelioma,
benign mesothelioma,
solitary fibrous tumour.
Incidence:
LFPT represents a rare,
slow-growing neoplasm (2.8/100,000 patient)
Although found in all age groups,
over 50% of cases are encountered in patients during the 6th and 7th decades of life.
LFTP affects male and female patients,
with a slight female predominance reported in some studies.
There is no apparent genetic predisposition and no relationship to exposure to asbestos,
tobacco,
or any other environmental agent.
Location:
LFTP may be a predilection towards the mid to lower zones of the chest.
These tumors usually arise from the visceral pleura (80%) and the remaining in the parietal pleura.
Clinical features:
This is a well circumscribed slow growing painless tumour.
Clinical symptoms depend on the size and location of the tumor,
where symptoms are usually related to compression rather than infiltration of the adjacent tissue.
Localized fibrous tumors of the pleura are usually asymptomatic in their early stage and are often discovered incidentally as an incidental finding on a routine chest radiograph or for evaluation of an unrelated disease.
In cases which are symptomatic,
patients present with cough,
dyspnea,
hemoptysis and chest pain.
Chest pain occurs more commonly in the patient whose tumor arises from the parietal pleura.
Paraneoplastic syndromes such as hypoglycemia,
digital clubbing and hypertrophic osteoarthropathy are uncommon,
but when they are asociated with an intrathoracic mass they may suggest the diagnosis of LFTP.
Digital clubbing and hypertrophic pulmonary osteoarthropathy (Pierre-Marie-Bamberg syndrome) have been described in 10% to 20% of patients with either benign or malignant SFTP.
Their causes are unknown.
The incidence of refractory hypoglycemia is low at 3% to 4%. The tumor secretes insulin-like growth factor II.
Although most such tumours occur in the pleura,
they have also been report from a large range of extra-pleural sites (meninges,
nose,
oral cavity,
subcutis,
deep soft tissues,
thyroid,
mediastinum,
lung,
pericardium,
heart,
peritoneum,
prostate..).
The benign tumors are slow growing and compress adjacent structures but usually do not invade.
Histologic Characteristics:
On microscopic sections,
the pattern has been described as a mixture of spindle cell patterns,
sometimes a patternless pattern.
Immunohistochemically,
LFTP commonly express CD34,
vimentin,
bcl-2 and CD99.
Although malignant tumors may occur,
benign tumors are far more common outnumbering the malignant tumors by a ratio of 7 to 1.
Gross features:
- Well circumscribed,
lobulated,
partially encapsulated tumour.
- The size of the tumour ranges from 1 to 25 cms in diameter.
- The tumour has a tan white,
firm,
homogenous cut surface.
- There may be focal haemorrhagic and myxoid areas.
Treatment and prognosis:
Solitary fibrous tumors of the pleura are rare neoplasms that fortunately are benign 80% of the time.
They are readily curable with careful,
complete resections.
Although the less common malignant variety of SFTP has a higher recurrence rate and higher tumor-related mortality,
aggressive surgery and careful postoperative surveillance may still permit long-term survivals in as many as 70% of these patients.
Recurrence after surgical resection is most often located in the same hemithorax and may occur up to 17 years after resection.
Intrathoracic recurrence may be fatal because of mediastinal compression and inferior vena cava obstruction.
Metastases,
if present,
are usually blood borne and are located,
by order of frequency,
in the liver,
central nervous system,
spleen,
peritoneum,
adrenal gland,
gastrointestinal tract,
kidney,and bone.