Five months later, the mass began to enlarge and drain copious amounts of purulent material. He then experienced weakness in the lower right leg and right-sided seizures. A three-dimensional CT scan of the head found a large, ringed lesion in the left occipital lobe (Fig 4). He was treated with corticosteroids and phenytoin, then referred for further evaluation.

Past medical history found no pulmonary disease and was significant for tobacco use and tuberculosis exposure in the 1950s without development of active disease. Physical examination revealed a fever of 101°F and an oval-shaped, erythematous mass measuring 3 X 5-cm in his right upper back with a nondraining fistulous tract at its center. The lungs were clear to auscultation, but there was a II/VI systolic murmur in the lower left sternal border. Neurologic examination was nonfocal. The hemoglobin was 10.5 g/dL with a white blood cell count of 7.45 X 10^9/L and a platelet count of 345 X 10^9/L. The electrolytes and the liver function tests were normal.

On hospitalization, a CT-guided biopsy of the paraspinal mass was negative for nocardia, acid fast bacilli, and malignancy. An echocardiogram showed no evidence of vegetative lesions. Bronchoscopy was negative for histopathology but was remarkable for the presence of sulfur granules. Magnetic resonance imaging of the brain showed decreasing edema and increased hemosiderin deposition around the lesion. Cultures of the paraspinous fistula tract grew Actinobacillus actinomycetemcomitans that was positive for B-lactamase.

Treatment consisted of 2 g of intravenous ceftriaxone twice daily for an A actinomycetemcomitans infection, 600 mg of rifampin daily for synergy, and penicillin G four million units intravenously every six hours for a presumed Actinomyces sp infection. After eight weeks of this therapy, one year of 500 mg of penicillin VK every six hours was completed. Currently, two and one-half years after initial diagnosis, the patient remains asymptomatic with no clinical or radiologic evidence of infection or cancer.

Discussion

Q fever, due to infection with C burnetii, is rare in the United States with fewer than 30 cases annually reported between 1978 and 1986.[1] Animal reservoirs include cattle, sheep, and goats, with parturient cats being implicated in the northeast and Canada.[1,2] Humans are infected by inhalation of shed organisms, and symptoms include headaches, fevers, chills, and myalgias. Diagnosis is confirmed serologically.[1] Q fever pneumonia is usually benign with the presence of multiple or single round segmental densities on chest roentgenogram.[3] Resolution may require up to 70 days. Pathologic features can resemble inflammatory pseudotumors with mixed alveolar and interstitial pneumonic consolidation.[3] Relapse of Q fever has been demonstrated in animal models receiving radiation and corticosteroids.[4] Chronic Q fever is noted for the presence of endocarditis that occurs most frequently in previously damaged heart valves.[1,4]

Histoplasmosis is another chronic infection that can present as a pseudotumor. Pulmonary disease may result in an intense granulomatous reaction with caseation necrosis that may lead to either an acute or chronic process or disseminated histoplasmosis.[5,6] The inflammatory process frequently spreads to the mediastinal lymph nodes adjacent to the main stem bronchi. When collagen production occurs, it may progress to entrap vital structures such as the superior vena cava.[6] Collagen production can lead to fibrosing mediastinitis, which may progress to superior vena cava syndrome.

A actinomycetemcomitans is named for its association with Actinomyces sp[7,8] and is part of the endogenous mouth flora.[9-11] Pulmonary infections are rare, and spread to the lungs has been postulated either by a hematogenous route or by aspiration.[12] Infection can be necrotizing as in our case with chest wall and rib destruction.[7,8,12] Like A actinomycetemcomitans, Actinomyces sp infection can progress to tissue destruction and abscess formation as well as formation of draining sinuses with sulfur granules.13 Central nervous system involvement also is rare with hematogenous spread or direct extension as the suspected routes.[13,14] A pulmonary lesion with neurologic symptoms suggests lung carcinoma with cerebral metastasis. Brain abscesses generally are contrast-enhancing and frequently occur in the frontal and temporal lobes.[13]

The diagnostic approach to a radiographically demonstrated solitary pulmonary nodule should consider the patient's age and social history, the nodule's size and character, the presence of calcifications, and doubling time.[15,16] A CT scan may be useful when analyzing indeterminate lesions, since benign lesions are often more dense than malignant lesions.[17] A patient's age is important, with one study showing that 65% of nodules in men over the age of 60 years were malignant.[16] Patients from endemic areas might benefit from skin testing for tuberculosis, histoplasmosis, or coccidioidosis.[15]

A nodule is defined as a round and well-circumscribed lesion. Shaggy-bordered nodules are more commonly malignant.[17] The presence of calcifications frequently excludes malignancy, except "scar" carcinomas and pulmonary masses larger than 3 cm in diameter.[15,17] Finally, doubling time (by volume) is a useful indicator, with nodule doubling times of fewer than 11 days and greater than 465 days often being benign.[16] Although there are many causes of a solitary nodule, the differential diagnosis and subsequent treatment can be simplified when a systematic approach is employed. Common causes of nonmalignant solitary lesions are listed in the Table.

Although congenital, arteriovenous malformations can be present for years prior to vessel dilation. They are subpleural-based, circumscribed, and noncalcified.[16,18] The rare rheumatoid nodules usually are peripheral and well circumscribed. Hamartomas occur most often in the fourth decade and are round, lobulated, and subpleural masses.[18]

Fibromas are collections of fibrous mesothelia that occur in the fourth to seventh decades. They measure a few centimeters in diameter and are well circumscribed with a capsular layer of visceral pleura.[19] Their appearance is a whorled due to the presence of spindle cells admixed with collagen, and the lesions often are associated with hypertrophic pulmonary osteoarthropathy.[19]

Spindle cell carcinoid has no sex predilection and is peripherally located, unencapsulated, and well circumscribed.[19] Sclerosing hemangiomas are seen most often in middle-aged women and are frequently found in the lower lobes. The lesion is well circumscribed, is usually smaller than 5 cm in diameter, and is subpleural with multiple foci of calcification.

Use of the term pseudolymphoma remains controversial; some consider this lesion to be a well-differentiated lymphoblastic lymphoma.[19] The lesions are well circumscribed and noncalcified, and they frequently occur in middle age. Polymorphic lymphoid infiltrates are seen with numerous germinal centers and present a polyclonal pattern on immunohistochemical staining.[19]

Inflammatory pseudotumors, also known as plasma cell granuloma, histiocytoma, and fibroxanthoma, are the most common benign growth in children.[16] There is a slight predominance for the left upper lobe and a loose association with increased sedimentation rate, thrombocytosis, and polyclonal gammopathy.[18] One third have had a preceding infection and are culture-positive for Bacteroides species, Corynebacterium equi, C burnetii, intracellular mycobacteria, or Mycoplasma pneumoniae.[18] Lesions are solid, well circumscribed, and unencapsulated collections of fibrous tissue, predominantly spindle and plasma cells.[19] Treatment often includes surgery, but radiation, corticosteroids, and antibiotics have been successful options.[18]

Mycetomas compose a solid, rounded mass with a spherical acuity separated by air-space. The size varies from 3.5 to 5.5 cm with occasional calcification.[15] Coccidiomycosis often involves the lower lobes with rare cavitation, and is frequently asymptomatic. Blastomycosis produces a solid mass and can mimic malignancy with hilar and mediastinal lymphadenopathy.[16] Cryptococcosis occurs in the middle-aged and in those with underlying processes such as chronic obstructive pulmonary disease, systemic lupus erythematosus, hematologic malignancies, and chronic corticosteroid use.[15] It forms a solitary lesion 2 to 10 cm in diameter that is pleural-based, confined to a single lobe, and rarely calcified.[15] It is not usually associated with mediastinal or hilar lymphadenopathy but is frequently mistaken for carcinoma of the lung.

Finally, loculated pleural effusions can occasionally produce a pseudotumor that disappears when the effusion is treated effectively.

Appreciation is expressed to Thane Smith for photographic assistance with the images.

References

1. Mandell GL, Gordon RG Jr, Bennett JE, eds. Coxiella burnetii. Principles and Practice of Infectious Diseases. 3rd ed. Churchill Livingstone, Inc; 1990:1472-1476.
2. Pinsky RL, Fishbein DB, Greene CR, et al. An outbreak of cat-associated Q fever in the United States. J Infect Dis. 1991;164:202-204.
3. Janigan DT, Marrie TJ. An inflammatory pseudotumor of the lung in Q fever pneumonia. New Engl J Med. 1993;308:86-88.
4. Raoult D, Brouqui P, Marchou B, et al. Acute and chronic Q fever inpatients with cancer. Clin Infect Dis. 1992;14:127-130.
5. Wilson J, Braunwald E, Isselbacker K, et al. Principles of Internal Medicine. 17th ed. McGraw Hill, Inc; 1991:745-746.
6. Levitt R, Glazer H, Gutierrez F, et al. Magnetic resonance imaging of spiral vein graft bypass of superior vena cava in fibrosing mediastinitis. Chest. 1986;90:676-680.
7. Bowker CM, Connellan SJ, Freeth MG. A case of thoracic actinobacillus infection. Resp Med. 1992;86:53-54.
8. Morris JF, Sewell DL. Necrotizing pneumonia caused by mixed infection with Actinobacillus actinomycetemcomitans and Actinomyces israelii: case report and review. Clin Infect Dis. 1994;18:450-452.
9. van Winkelhoff AJ, Overbeek BP, et al. Long-standing bacteremia caused by oral Actinobacillus actinomycetemcomitans in a patient with a pacemaker. Clin Infect Dis. 1993;16:216-218.
10. Loesche WJ. Bacterial mediators in periodontal disease. Clin Infect Dis. 1993;16(Suppl 4):S203-S210.
11. Kaplan AH, Weber DJ, Oddone EZ, et al. Infection due to Actinobacillus actinomycetemcomitans: 15 cases and review. Rev Infect Dis. 1989;11:46-63.
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13. Smego RA Jr. Actinomycosis of the central nervous system. Rev Infect Dis. 1987;9:855-865.
14. Pavicic MJAMP, van Winkelhoff AJ, de Graaff J. In vitro susceptibilities of Actinobacillus actinomycetemcomitans to a number of antimicrobial combinations. Antimicrob Agents Chemother. 1992;36:2634-2638.
15. Fraser RR, et al. Diagnosis of Diseases of the Chest. 3rd ed. WB Saunders Co; 1989;2:793-1077.
16. Fishman AP, et al. Pulmonary Diseases and Disorders. 2nd ed. McGraw-Hill; 1988;2:1383-1431.
17. Viggiano RW, Swensen SJ, Rosenau EC. Evaluation and management of solitary and multiple pulmonary nodules. Clin Chest Med. 1992;13:83-95.
18. Scully RE, et al., eds. Weekly clinicopathological exercises. New Engl J Med. 1994;330:1439-1446.
19. Kobzik L. Benign pulmonary lesions that may be misdiagnosed as malignant. Semin Diagn Pathol. 1990;7:129-138.

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