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|Year : 2012 | Volume
| Issue : 4 | Page : 328-330
Pulmonary nodules with cavitary mass in a flour mill worker
JM Joshi1, KS Barve2, S Basu3
1 Department of Pulmonary Medicine, TATA Memorial Hospital, Mumbai, Maharashtra, India
2 B Y L Nair Hospital, Mumbai, Maharashtra, India
3 Radiation Medicine Centre, TATA Memorial Hospital, Mumbai, Maharashtra, India
|Date of Web Publication||4-Jan-2013|
K S Barve
B Y L Nair Hospital, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Joshi J M, Barve K S, Basu S. Pulmonary nodules with cavitary mass in a flour mill worker. J Postgrad Med 2012;58:328-30
We present a case of silicosis with a long standing unusual occupational exposure to silica dust in a flour mill worker presenting with a cavitary progressive massive fibrosis (PMF). The lesion showed an increased uptake of fluorodeoxygenase (FDG) on positron emission tomography (PET) suggesting metabolic activity, which raised the possibility of malignancy or active tuberculosis.
A 50-year-old man, chronic smoker, working in a flour mill for last 30 years, presented with 3 year history of dry cough and progressive dyspnea. He had received empirical tuberculosis therapy multiple times without any relief in symptoms. His vital parameters were normal with pulse oximetry showing exercise oxygen saturation of 98%, which decreased to 90% after an exercise. Chest auscultation revealed bilateral crackles. Laboratory investigations - hemogram, renal function test, liver function test were within normal limits. Mantoux test was negative. Chest radiograph showed bilateral nodular opacities with cavitary mass lesion in left middle zone [Figure 1]. High resolution computed tomography (HRCT) [Figure 2]a and b showed discrete nodules throughout lung parenchyma bilaterally, mediastinal, and hilar lymph nodes showing egg shell calcification and cavitary mass in left upper lobe. Spirometry showed a restrictive abnormality and reduced diffusion capacity of the lung for carbon monoxide (DLCO). FDG PET scan [Figure 3] revealed a conglomerated mass of intense FDG uptake in middle zone of left lung and focal area of uptake in mediastinum. The patient used a red colored high silica containing stone commonly known as "Agra stone" in the flour mill grinder, which generated significant dust during chiseling [Figure 4]. Sputum cytology and bronchial washings were negative for malignant cells. Sputum smear was negative for acid fast bacilli, and culture revealed no growth of Mycobacterium tuberculosis. The patient was, therefore, diagnosed as case of chronic silicosis with cavitary PMF.
|Figure 1: Chest radiograph showed bilateral nodular opacities with cavitary lesion in left middle zone|
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|Figure 2 (a and b): High resolution computed tomography (HRCT) showing discrete nodules throughout lung parenchyma bilaterally with mediastinal and hilar lymph nodes showing egg shell calcification and cavity in left upper lobe with surrounding centrilobular nodules|
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|Figure 3: Fluorodeoxygenase (FDG) positron emission tomography scan showing a conglomerated mass of intense FDG uptake in middle zone of left lung|
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Silicosis is a fibrosing disease of lungs caused by inhalation, retention, and pulmonary reaction to crystalline silica due to an occupational exposure to silica particles of respirable aerodynamic size.  3 forms of the disease are well characterized- chronic (classic), accelerated, and acute. Radiologically, it is characterized by nodular lesions in upper zone and mid zone, coalescence of the lesions to large masses called progressive massive fibrosis (PMF). Silicosis is seen commonly in occupations like mining, quarrying, drilling, tunneling, sandblasting, construction work, and foundries. However, a significant exposure to silica dust can also occur in unusual occupation like working in flour mill  due to an exposure to "Agra stone"- a high silica stone dust. These uncommon occupational exposures usually go unrecognized as in our patient.
Positive FDG-PET uptake in lung as well as mediastinum in PMF with cavitation raised suspicion of malignancy or tuberculosis.  Also, as a positive mediastinal uptake may be confused with a primary complex in tuberculosis or an N1/2 lymph node in lung cancer, both these conditions were excluded by negative sputum culture for mycobacterium and negative bronchial washing cytology for malignant cells. Not all radiographic nodal and intrapulmonary lesions are FDG avid, thus showing that PET identifies "disease activity." Even non-infectious inflammatory process associated with pulmonary reaction to crystalline silica may result in vasculitis,  ischemic necrosis, and FDG uptake in the areas of cavitary PMF.  However, it has been noted that in contrast to malignancies, not all non-malignant radiographic lesions (>1 cm) show FDG uptake [Table 1].
In conclusion, a high index of suspicion for occupational lung diseases is required, particularly in small scale industries. Positive FDG-PET in patients of silicosis, even in the presence of PMF and cavitation, should not be considered diagnostic of malignancy or tuberculosis.
| :: References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]