Saturday, 23 November 2013

Benign lung tumors - The Causes

Benign lung tumors, growth from many different structures in the lung, is defined as a conditions of abnormal  cell growth with no tendency of spreading or masses that push normal cells out of the way rather than invading surrounding tissue restricted to a limited area in the lung. Approximately one out of 500 chest radiographs shows the incidental finding of a solitary pulmonary nodule and almost one half of these pulmonary lesions are caused by a tumor. Unfortunately, only 2% to 5% of all lung tumors are of benign origin, e. g. lipoma, fibroma, hamartoma, and chondroma, and the majority are malignant neoplasms, most commonly primary lung cancer followed by metastases of extrapulmonary primary carcinomas. According to the study by Universitätsklinik für Pneumologie(a)
C. Causes
1. Infectious and inflammatory causes of benign lung tumors
a. An infectious fungus such as coccidioidomycosis
Coccidioidomycosis refers to the spectrum of disease caused by the dimorphic fungi Coccidioides immitis and Coccidioides posadasii. Clinical manifestations vary depending upon both the extent of infection and the immune status of the host. Coccidioidomycosis has been reported to involve almost all organ systems; however, pulmonary disease is the most common clinical manifestation. The incidence of coccidioidomycosis continues to rise, and primary coccidioidal pneumonia accounts for 17 to 29% of all cases of community-acquired pneumonia in endemic regions. The majority of patients with coccidioidomycosis resolve their initial infection without sequelae; however, several patients develop complications of disease ranging in severity from complicated pulmonary coccidioidomycosis to widely disseminated disease with immediately life-threatening manifestations, according to the study by the University of California-Davis(5).
Other study report a case of a 61-year-old gentleman presented with shortness of breath, cough, weight loss, but no fever or hemoptysis. His physical exam was unremarkable except for decreased air entry on both lung fields, and axillary and inguinal lymphadenopathies. Computed tomography of the chest showed bilateral cavitary lung lesions, biopsy of which showed non caseating granulomas, and tissue culture showing Histoplasma capsulatum(6).
b. Tuberculosis (TB)
Chordoma is an uncommon tumor initially believed to be benign due to the rarity of its metastasis. Cytological, morphological, and immunohistochemical features of chordoma, relating to its origin from notochordal remnants, allows for its accurate diagnosis. According to the study by University of Saskatchewan, there is a report of a 75-year-old man with a known history of tuberculosis (TB) presented with shortness of breath and a dry cough. A chest X-ray demonstrated a diffuse, infiltrative miliary pattern in both lungs. Bronchial washings submitted for culture and cytological examination did not identify any tuberculous bacilli. Fine needle aspiration cytology (FNAC) showed focal areas of myxoid regions with small, round, uniform mononuclear cells. There was a documented past history of chordoma arising from the L2 vertebrae. Because of the rarity of this lesion in the lung and the limited diagnostic material available with a clinical history of TB and lumbar chordoma, the pathological report rendered on the FNAC was “atypical cells suspicious for metastatic chordoma(7).
c. A lung abscess
Capnocytophaga species are known commensals of the oral cavity of humans and animals (mainly dogs and cats) and are a rare cause of respiratory tract infections. There is a report of a case of cavitary lung abscess caused by a Capnocytophaga species in a patient with a metastatic neuroendocrine tumor, according to the study by Memorial Sloan-Kettering Cancer Center(8).
d. Round pneumonia
The differential diagnose between round pneumonia and a neoplastic process is difficult to make. In this report, all of cases of round pneumonia have resolved clinically and radiographically with antibiotic therapy, according to the study by (9).
e. Parasitic infections
According to the study by Department of Surgery, Mayo Clinic, Multiple benign pulmonary nodules are rare and are from a variety of etiologies. Infectious causes, such as histoplasmosis, tuberculosis, or parasitic infections, usually require biopsy for confirmation(9a).

2. Diseases casues of benign lung tumors
d. Rheumatoid arthritis
In the study to examine the role of lung disease in rheumatoid arthritis from a clinical, epidemiologic, pathophysiologic, and therapeutic perspective, showed that lung disease in rheumatoid arthritis is a heterogeneous and oftentimes serious condition, with a profound impact on patient wellbeing and survival. Advances in the understanding of its etiology and targeted application of available, as well as development of new, more specific therapeutics will be of benefit to patients with rheumatoid arthritis who are suffering from lung disease(10).
e. Wegener granulomatosis
Wegener’s granulomatosis is a type of vasculitis, or inflammation of the blood vessels. Wegener’s granulomatosis is a systemic vasculitis that primarily involves the upper and lower respiratory tracts and kidneys. Pulmonary Wegener’s granulomatosis can present with multifocal lung involvement or solitary lung lesions with no evidence of extrapulmonary disease, according to the study by the research team of Dr. S Uppal.(11).
f. Sarcoidosis
There is a report of a case of a 65-year-old woman with a high initial index of suspicion for lung malignancy. Clinicians should always be aware that sarcoidosis enters the differential diagnosis of patients presenting with a lung mass that encases and narrows bronchial and vascular structures with associated pericardial effusion. Rarely, pleural effusion can be the presenting symptom of disease relapse despite maintenance treatment(12).
g. Leiomyoma
Benign metastasizing leiomyoma, is rare but occurs from a low-grade leiomyoma that most commonly spreads from the uterus(13).
h. Meningiomas
Meningiomas are generally benign tumors, but rarely metastasize outside of the central nervous system. There is a report of a 25-year-old female was admitted to our institute because of an abnormal shadow on her chest x-ray. A computed tomography (CT) scan showed a 3-cm, well- circumscribed mass in the right lower lobe of the lung. We performed thoracotomy and resected three pulmonary tumors at the right lung and diaphragm. Histological examination revealed a benign meningothelial meningioma. Six months later, she complained of heaviness of her head and a head CT scan revealed an intracranial mass(13a).

3. Birth defected causes of benign lung tumors
The relationship between congenital cystic adenomatoid malformation (CCAM) and pleuropulmonary blastoma (PPB), whether causal, correlational, or coincidental, remains controversial. In the study of Seventy-four CCAMs resected over the study period in 129 children diagnosed with CCAM. Five PPBs were diagnosed during the study period. Three of the 5 PPB cases were initially diagnosed as CCAMs. These PPBs were not clinically or radiologically distinguishable from CCAMs, found that asymptomatic cystic lung malformations represent a therapeutic dilemma. In this cohort, the incidence of PPB among apparently benign lung lesions was 4%. No clinical or radiological markers differentiated benign CCAMs from PPBs. Our experience provides further justification for resection of all CCAMs(14).


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