A 75-year-old Japanese female was admitted to our hospital with a painful mass on the left anterior chest wall for eight days without any other symptoms. She presented at another hospital with left chest pain 3 days previously without any features suggestive of pneumonia including cough, sputum or dyspnea. Chest computed tomography (CT) obtained at the other hospital showed a mass in the left upper pulmonary lobe without any chest wall abnormalities (Fig. 1). As a result, lung cancer was suspected. She had no significant past medical history, nor did she have any history of smoking or alcohol consumption. She had no known tuberculosis exposure, and had not traveled outside Japan. She had not previously received a pneumococcal vaccine. Her vital signs were within the normal limits. A physical examination revealed a palpable, pink erythematous, warm and tender mass measuring 8 cm in size located close to the sternum overlying the left first to third intercostal spaces (Fig. 2). Her breath sounds were slightly decreased over the left upper zone, but there were no rales. A laboratory test revealed a high white blood cell count (14,310 cells/mm3 with 87.9% of neutrophils) and an elevated C-reactive protein level (33.35 mg/dL). Moreover, she was diagnosed with diabetes mellitus because of her elevated HbA1c level (7.5%). A chest X-ray obtained on admission demonstrated a 7x5 cm mass in the left upper lung field (Fig. 3). Chest contrast-enhanced CT showed a gas-containing lung abscess in the left upper lobe and a chest wall abscess (Fig. 4). There was some air in the first sternocostal joint and no pleural effusion. These findings were thought to indicate that lung abscess had directly extended into the chest wall through the sternocostal joint. Chest ultrasonography showed almost the same findings as those obtained from CT. Surgical debridement of the subcutaneous and intramuscular fluid collection was carried out under local anesthesia (Fig. 5). Then, under ultrasonographic guidance, an 8-Fr aspiration catheter (Argyle  Aspiration Catheter; Covidien, Japan) was percutaneously inserted into the lung abscess, and odorless pus was drained (Fig. 6). Gram staining of the pus revealed numerous Gram-positive cocci, and empiric antimicrobial therapy with intravenous meropenem and clindamycin was initiated. On the 5th day, the culture specimens obtained from the lung and subcutaneous abscess grew S. pneumoniae. Mycobacterial and anaerobic cultures of the same specimens and two sets of blood cultures were all negative. Antibiotic susceptibility testing was performed by lung and subcutaneous drainage cultures. The isolate was susceptible to penicillin, ceftriaxone, and vancomycin, and resistant to erythromycin. The patient was considered to have a lung abscess attributable to S. pneumoniae which had directly extended into the chest wall. The antibiotic therapy was changed to intravenous ampicillin/sulbactam according to the results of antimicrobial susceptibility testing. After 16 days of antimicrobial therapy, the catheter was removed because the drainage had become serous and chest CT showed a remarkable improvement (Fig. 7A and B). Oral amoxicillin/clavulanic acid was used for 1 week after 3 weeks of intravenous antibiotic therapy, and the patient was discharged on the 25th day of hospitalization. At a follow-up examination at 1 month after the patient's discharge, she was asymptomatic and demonstrated normal chest radiography findings (Fig. 7C).
Three days before admission, chest CT showed a mass in the left upper pulmonary lobe without any chest wall abnormalities (arrows).