INTRODUCTION: Mesenchymal cystic hamartoma of the lung was first described in 1986. It is a rare disease and the prevalence remains unknown. The characteristic clinical and radiographic features are a combination of small nodules and multiple bilateral thin-walled cystic lesions.
CASE PRESENTATION: A 54-year-old African American female presented for suspected sacral osteomyelitis. Her medical history was significant for a hysterectomy, and transverse myelitis of 8 years. Her medications included baclofen and amitriptyline. She denied ever smoking, illicit drug use, or alcohol abuse. She was born in New York City and worked as a seamstress. She denied any cough, sputum, or hemoptysis, and never had chest pain, dyspnea, paroxysmal nocturnal dyspnea, or orthopnea. On physical exam she was not in acute respiratory distress. Her vital signs were significant for a temperature of 102.4° F; her oxygen saturation was 98% on room air. She had temporal wasting. There were clear breath sounds bilaterally. She was noted to have a stage IV sacral decubitus with a purulent exudate. The rest of her physical exam was unremarkable. Laboratory data revealed a normal white blood cell count and differential. Serum chemistry was unremarkable. Chest radiograph showed multiple to innumerable thin-walled cystic structures replacing the mid and lower lung zones bilaterally. A few nodular densities were identified in the upper lobes bilaterally. This prompted a CT chest which revealed numerous bilateral noncalcified subpleural nodules 0.5 centimeters, and thin-walled bilateral lung cysts with various sizes ranging from 2-7 centimeters in diameter. She could not recall when she had her last chest radiograph and was never told she had an abnormal film.
DISCUSSIONS: The differential diagnosis for cystic lung disease includes lymphangiomyomatosis, Langerhan's histiocytosis, mesenchymal cystic hamartoma, cystic adenomatoid malformation, bronchogenic cyst, placental transmogrification, metastatic endometrial stromal sarcoma, cystic bronchiectasis, and bullous emphysema. The best test to confirm a diagnosis is a lung biopsy, however our patient was unstable and died from septic shock secondary to osteomyelitis. Nonetheless, our working diagnosis was mesenchymal cystic hamartoma based on the classic radiographic findings. In mesenchymal cystic hamartoma there is a propagation of new nodules and enlargement of cysts in the absence of fever, weight loss, cough, sputum production, and severe dyspnea. In other words the clinical course is indolent. The nodules are thought to occur first and when they reach 0.5 to 1 centimeter, small cysts form. During the natural history of the disease, transformation of a nodule into a cyst may be due to destruction of the structural integrity of the walls of bronchioles or alveolar ducts by the proliferating cells. The nodules and cysts increase very slowly over a period of many years and represent different stages of the disease. New nodules continue to appear when the cysts are already developed. The cysts become lined with normal or metaplastic bronchiolar epithelium. Bronchial, phrenic, or intercostal arteries supply the cysts and become hypertrophied as the cysts enlarge and destroy the normal architecture of the lung. Therefore, serious complications of this disease include pulmonary hemorrhage into a cyst from a large systemic artery, pneumothorax or hemothorax, and malignant transformation. Since the disease has a benign course in most patients, resection of asymptomatic nodules and cysts are not routinely recommended. A confirmatory biopsy is needed to rule out metastatic endometrial stromal carcinoma, however our patient had a hysterectomy.
CONCLUSION: Mesenchymal cystic hamartoma of the lung is thought to be a low-grade sarcoma of the lung. This unusual entity is often diagnosed as an incidental finding on chest radiograph and may have a potentially fatal complication. Therefore, patients should be aware of their diagnosis, and be prepared to contact a physician immediately in case they experience hemoptysis.
DISCLOSURE: Sonali Sethi, None.