Thoracic actinomycosis simulating neoplastic disease in Pediatrics

Instituição: Departamento de Pediatria da Faculdade de Ciências Médicas da Universidade Estadual de Campinas (Unicamp), Campinas, SP, Brasil 1Doutor em Saúde da Criança e do Adolescente pela Unicamp; Professor Doutor da Faculdade de Ciências Médicas da Unicamp, Campinas, SP, Brasil 2Doutora em Ciências Médicas pela Unicamp; Professora-Associada da Faculdade de Ciências Médicas da Unicamp, Campinas, SP, Brasil ABSTRACT


Introduction
Chest wall lesions in childhood include a wide range of pathologies; among the benign lesions, lipoma, neurofibroma, hemangioma, lynphangioma, and mesenchymal hamartoma stand out.Malignant lesions can be related to rhabdomyosarcoma and neuroblastoma.Manifestations of systemic diseases, such as leukemia, lymphoma, Langerhans cell histocytosis, and infections like tuberculosis and actinomycosis, may also cause chest wall lesions (1) .
Thoracic actinomycosis is much more common in adults than in children and in male patients.Risk factors in children include dental caries, trauma, severe malnutrition, and uncontrolled diabetes mellitus (2,3) .We present the case of a ten-year old with pulmonary actinomycosis initially simulating malignant disease.

Case report
ten-year-old female patient, previously healthy, was admitted with a history of continuous chest pain during the past three months, with a mass in the left anterior chest wall.In the last two months, she sought several health services, with no diagnosis, and was initially referred to a Pediatric Oncology Center with the hypothesis of malignant disease.
Physical examination showed a mass of nearly 8.0cm of diameter in the left inframammary region, hardened and with no signs of infection, as well as absence of caries or lymph node megaly and weight and height appropriate for age and sex.Laboratory tests showed: hemoglobin of 10.1g/ dL, leukocyte count of 12,350/mm 3 (66% of which were polymorphonuclear, 30% lymphocytes, and 4% monocytes), platelet count of 345,000/mm 3 , and high C-reactive protein (10.5mg/dL).Assessment of liver and kidney functions was normal.Tuberculin test was negative, and chest radiograph revealed a homogenous opacity in the upper left hemithorax, with increase in adjacent soft tissues (Figure 1).The contrast computed tomography scan showed a soft tissue mass in the left pulmonary lobe expanding to the left anterior mediastinum and the left anterior chest wall (Figure 2).
The anatomohistologic study revealed an inflammatory process with no evidence of malignancy.Hematoxylineosin (HE) staining revealed sulfur granules, suggesting Actinomyces.Investigation for alcohol-acid resistant bacilli was negative.Actinomyces israelii was identified in the culture of biopsy fragments (5% sheep's blood agar for anaerobic culture, Center for Disease Control).
The patient received crystalline penicillin (200,000units/ kg/day) during three weeks, followed by six months of amoxicillin (40mg/kg/day).During the first week of treatment, she showed clinical and radiograph improvement.She was followed up every two weeks until completing oral antibiotic therapy and remained asymptomatic two years after the end of the treatment.
Thoracic actinomycosis is a rare disease in childhood (3)(4)(5)(6) .Bartlett et al (2) , in a literature review of studies conducted after computed tomography became available in 1975, identified 55 cases of thoracic actinomycosis in children and adolescents under 18 years old, mainly in boys (64%).
The most common findings in patients with thoracic actinomycosis are: chest wall mass (49%); pain (36%), generally located at the back of the elbow or at the axillary region; weight loss (35%); fever (35%); fistulas (15%); and hemoptysis (9%) (2,3) .Although some risk factors for infection have been described, such as the presence of dental caries, local trauma, foreign bodies, and uncontrolled diabetes (2,4) , their absence does not rule out the diagnosis of actinomycosis, as can be seen in the case described.Thoracic actinomycosis may be explained as a result of aspiration of Actinomyces and is also associated with tooth extractions.
The diagnosis of actinomycosis is frequently delayed because it is not considered in the differential diagnosis for chest wall mass (2,4) ; moreover, it is based on histology (sulfur granules).In the tissues, the bacteria develop into dense granules or microcolonies, called 'sulfur granules' due to its yellowish color, and may be observed on gross examination.In the series reported by Bartlett et al (2) , the diagnosis of actinomycosis was confirmed on histopathology in only 38% of patients.
Microorganisms of the Actinomyces genus are uniformly sensitive to penicillin, and the treatment is generally a combination of prolonged antibiotic therapy with surgical drainage.Despite the absence of available data to justify the optimal duration of treatment, most authors recommend that antibiotic treatment should last between six and 12 months, being administered intravenously at the beginning and then orally (2,3,(8)(9)(10)(11) .The evolution is satisfactory, rarely leading to death in children (2,12) .
The hypothesis of actinomycosis should always be considered in the differential diagnosis of chest masses, even in the absence of risk factors, which is important to guide microbiological and histological studies.

Figure 2 -Figure 1 -
Figure 2 -Contrast computed tomography scan showing the image of a large mass of soft tissue at the left upper lobe, expanding to the anterior mediastinum and the left anterior chest wall.The eighth rib is displaced anterolaterally (arrow)