Miliary mesothelioma
Michael Huncharek
Metastases in pleural mesothelioma usually occur late in the disease process. Diffuse involvement of the lung parenchyma is rare. A patient with miliary pulmonary parenchymal involvement with malignant mesothelioma is described. To our knowledge, this represents the first such case reported.
Malignant pleural mesothelioma is a relatively rare tumor that is becoming increasingly common. The tumor is characterized as a highly malignant neoplasm, with a mean survival time from diagnosis of approximately 12 months. Metastases occur late in the disease process, with common sites of spread being the contralateral lung, liver, kidneys, and adrenal glands.[1] Involvement of the contralateral lung is usually in the form of large nodules or pleural based lesions. Bilateral diffuse pulmonary involvement is unusual, and a miliary pulmonary parenchymal pattern of spread has not been previously reported to our knowledge. A case of pleural mesothelioma with a miliary radiographic presentation is described.
Case Report
The patient is a 61-year-old white woman who presented complaining of 3 months of increasing pleuritic left lower chest pain, dyspnea on exertion, and fatigue. She had had no change in her chronic cough or production of white sputum. One week prior to admission, the patient had presented to the emergency ward, where a chest x-ray film (Fig 1) showed a left-sided pleural effusion, which was found to be exudative. The findings from physical examination were remarkable for decreased breath sounds at the lung bases bilaterally, with some dullness to percussion of the left base.
A tuberculin skin test was positive. A workup in the hospital included thoracentesis (X4) and two pleural biopsies, all negative for granulomata, acid-fast organisms, or tumor. A liver-spleen scan and mammograms were normal. A chest x-ray film (Fig 2) and chest computed tomogram (Fig 3) obtained 1 week following admission showed a miliary pattern believed to represent miliary tuberculosis. The patient was started on therapy with isoniazid, rifampin, and ethambutol. She was discharged from the hospital in stable condition.
The patient’s medical history included a total abdominal hysterectomy with bilateral salpingo-oopherectomy 15 years earlier for menorrhagia. She had a 40-pack-year smoking history and remote exposure to a brother with active tuberculosis. She denied any toxic exposures or exposure to asbestos.
Over the subsequent 3 weeks, the patient’s weight decreased by 2.7 kg (6 lb), and she complained of anorexia, morning nausea, dyspnea on exertion, and continued left-sided pleuritic chest pain. A repeat chest x-ray film showed the miliary pattern previously described, as well as a persistent moderate left-sided pleural effusion. The patient was admitted to the hospital shortly thereafter for bronchoscopy, which was not performed due to poor pulmonary function. The forced vital capacity was 1.06 L, and the forced expiratory volume in 1 s was 0.74 L. Arterial blood gas analysis with the patient breathing room air showed a pH of 7.43, Pa[O.sub.2] of 63 mm Hg and Pa[CO.sub.2] of 44 mm Hg.
A bone marrow biopsy and liver biopsy were performed and were negative for acid-fast organisms; pathologic findings was negative. Streptomycin and pyrazinamide were added to her drug regimen, but the patient continued to show little improvement in her symptoms or chest x-ray findings. She was subsequently admitted to the hospital for open lung biopsy for definitive tissue diagnosis.
The findings from flexible bronchoscopy under anesthesia were unremarkable and showed no endobronchial lesions. Brushings and washings were taken, which proved negative. Open lung biopsy was performed, with pleural biopsy. The parietal and visceral pleura were found to be thickened and fibrosed. A frozen section was suggestive of mesothelioma. Microscopic sections showed malignant mesothelioma, with special staining indicating that the tissue was negative for carcinoembryonic antigen, and staining for keratin was positive. These findings were consistent with a diagnosis of pleural mesothelioma.
Discussion
Pleural mesothelioma is becoming an increasingly common tumor. Data from the United States Surveillance, Epidemiology, and End Results (SEER) program show that the age-adjusted incidence f or the years 1973 through 1987 increased two to three times,[2] ie, 0.6 cases per 100,000 to 1.7 cases per 100,000. During the same period, the rates among white male subjects alone more than doubled, rising from 0.7 cases per 100,000 in 1973 to 1.8 cases per 100,000 in 1984. Data derived from the Los Angeles County and New York State Cancer Registries further support the data provided by SEER.[3] The etiologic association between asbestos and mesothelioma is well documented. The increase in incidence of this tumor closely parallels the widespread commercialization of asbestos, which is responsible for the majority of cases.
Pleural mesothelioma is characterized as an aggressive tumor that spreads widely in the pleural space. Direct invasion of thoracic structures occurs, with eventual encasement of the affected hemithorax. Metastatic spread is seen late in the disease course and has been well documented in postmortem studies.[1]
Diffuse pulmonary parenchymal involvement in pleural mesothelioma is unusual. Although Uri et al[4] described a case of diffuse pulmonary metastases in pleural mesothelioma, the case presented herein is, to our knowledge, the first with a radiographic miliary pattern. Of importance is the histologic confirmation of the radiographic findings. Diffuse pulmonary metastases in a miliary pattern should be recognized as a possible presentation of pleural mesothelioma.
References
[1] Huncharek M, Muscat J. Metastases in diffuse pleural mesothelioma: influence of histological type. Thorax 1987; 42: 897-98 [2] Ries LAG, Hankey BF, Miller BA, Hartman AM, Edwards BK. Cancer statistics review, 1973-1988 (NIH publication 91-2789). Bethesda, Md: National Cancer Institute, 1991. [3] Spirtas R, Beebe GW, Connelly RR, Wright WE, Peters JM, Sherwin RP, et al. Recent trends in mesothelioma incidence in the United States. Am J Ind Med 1986; 9: 397-407 [4] Uri AJ, Schulman ES, Steiner RM, Scott RD, Rose LJ. Diffuse contralateral pulmonary metastases in malignant mesothelioma: an unusual radiographic presentation. Chest 1988; 93: 433-34
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