Pulmonary dirofilariasis and transitional cell carcinoma. Benign lung nodules mimicking metastatic malignant neoplasms

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Human pulmonary dirofilariasis in a patient whose clinical condition altered during follow-up

Pulmonary dirofilariasis is a rare disease. We have experienced a case which developed pleural effusion while being followed, rendering it difficult to establish the diagnosis. The patient, a 53-year-old woman, had previously undergone two operations; one for uterine cancer and another for breast cancer. She developed a cough in February 2002, and chest computed tomography (CT) scans disclosed a nodular mass in the right lung. A biopsy revealed a fibrous nodule with macrophage aggregation. Pleural effusion was demonstrated on chest CT scans performed in May. As the possibility of malignant tumor could not be ruled out, an operation was undertaken. The nodular lesion showed marked coagulation necrosis, and dead parasites were noted in the vascular lumen. The parasites had the characteristic morphological features of Dirofilaria immitis. Immunological studies produced a positive test result for the anti-dirofilaria immitis antibody; hence a diagnosis of pulmonary dirofilariasis was made.

Human pulmonary dirofilariasis: report of six cases

We report six cases of pulmonary dirofilariasis diagnosed at our laboratory with clinical and pathological features. The nodules of dirofilariasis were round in three cases as previously reported, however dumbbell-shaped in two cases. The nodule did not attach to the pleura in four cases. Microscopically, the nodules were granulomas composed of central coagulation necrosis and peripheral fibrosis with round cell infiltration, histiocytes, and multinucleated giant cells. Necrotic pulmonary artery with single or multiple sections of degenerated nematode was observed in the center of the nodule. Dilated bronchioles with inflammation were observed in the nodule in four cases. Collapse of the alveoli, organizing pneumonia, hemosiderin-laden macrophages were observed around the nodule. We suppose that the nodule is not an infarction but a granuloma caused by antigen released from the nematode. Because the pulmonary dirofilariasis is difficult to be differentiated from primary or metastatic lung carcinoma, and the inflammation exists around the nodule, the nodule should be removed surgically.

Human pulmonary dirofilariasis: analysis of 24 cases from São Paulo, Brazil

STUDY OBJECTIVE

To present the clinical, radiologic, and pathologic aspects of 24 cases of human pulmonary dirofilariasis (HPD) from São Paulo, Brazil.

DESIGN

Retrospective study of 24 patients with a confirmed diagnosis of HPD over a 14-year period (from February 1982 to June 1996).

SETTING

Thoracic Surgery and Pulmonary Division, University of São Paulo and Hospital Albert Einstein, São Paulo, Brazil.

RESULTS

Seventeen patients were male (70.1%) and seven were female (29.9%). Their mean age was 51.4 years. Fifty-four percent of the patients were asymptomatic and 75% had a well-circumscribed noncalcified peripheral subpleural pulmonary nodule on the chest radiograph and thoracic CT scan, located preferentially in the lower lobes. The diagnosis was made after thoracotomy and wedge resections in 16 patients, by videothoracoscopy in six, after a pleural biopsy in one, and after necropsy in one. The pathologic examination of all the nodules revealed a central zone of necrosis, surrounded by a narrow granulomatous zone and peripherally by fibrous tissue. Pulmonary vessels exhibit varying degrees of endarteritis. In all cases, a dead worm, usually necrotic and fragmented, was found.

CONCLUSIONS

A subpleural, noncalcified pulmonary nodule in the appropriate clinical and epidemiologic setting should alert the clinician, radiologist, or pathologist to the possibility of Dirofilaria. HPD should be considered in the differential diagnosis of pulmonary nodules.

Pulmonary infections mimicking cancer: a retrospective, three-year review

Pulmonary infections can mimic or occasionally co-exist with pulmonary neoplasms. In order to determine the frequency and nature of these infections, we conducted a retrospective analysis, covering a 3-year period, of patients who were referred to our center with presumed lung cancer but turned out to have pulmonary infection instead. The overwhelming majority of patients (93.3%) referred to "rule out" lung cancer were documented as having a neoplastic process, and only 1.3% had an infection. Fungal infections (histoplasmosis, cryptococcosis, coccidiomycosis) accounted for 46%, mycobacteria for 27%, bacteria for 22%, and parasitic lesions (dirofilariasis) for 5% of these infections. The most common clinical manifestations were cough and chest pain, and the most common radiographic finding was a solitary pulmonary nodule. There were no specific clinical or radiographic features predictive of either infection or neoplastic disease. All patients responded to specific anti-infective therapy with or without surgical excision. Our data indicate that pulmonary infections mimic neoplasms very infrequently. However, establishing a specific diagnosis is critical, since the management and outcome of these two processes are entirely different.

Human pulmonary dirofilariasis: a review

The authors presented a detailed summary of the geographical distribution, clinical and pathological aspects of human pulmonary dirofilariasis. Although benign, this zoonosis, of which Dirofilaria immitis is the major etiological agent, represents a medical problem since it produces symptoms which may be confused with neoplasia and thus may subject patients to unnecessary thoracic surgery. Of 229 cases cited in the literature, only 17 were reported in Brazil, despite the existence of highly favorable conditions for the transmission of this infection in man. Thus it may well be that this parasitic infection remains underdiagnosed. Finally, the importance of a differential diagnosis between dirofilariasis and pulmonary neoplasia is emphasized in cases where there is a solitary subpleural nodule ("coin lesion") present. In addition, the development and improvement of modern immunological diagnostic techniques are essential to distinguish this benign disease from other pathological conditions and thus avoid unnecessary surgery. These techniques may reveal the true prevalence of this parasitic infection in our environment.

Dirofilaria immitis: a rare, increasing cause of pulmonary nodules

Dirofilariasis is an unusual but increasing cause of solitary pulmonary nodules. In this study, we reviewed the entire experience with dirofilariasis at our institution. Five such patients were identified. In all patients, the Dirofilaria immitis infection manifested as a solitary pulmonary nodule, and all patients underwent thoracotomy for diagnosis. None required systemic treatment. D. immitis is found in dog, cat, wolf, coyote, and fox populations throughout the United States, but the highest concentrations have been noted in the eastern, southeastern, and southern coastal states. The distribution of human cases of D. immitis infection has a similar pattern. Pulmonary dirofilariasis should be included in the differential diagnosis of peripheral noncalcified pulmonary nodules, especially in endemic areas.

Pulmonary coin lesions caused by Dirofilaria immitis

The dog heartworm Dirofilaria immitis has been diagnosed by thoracotomy as the etiology of neoplastic-appearing nodules in two patients in the Peoria, Illinois area. This brings the total number of reported cases of human pulmonary dirofilariasis to approximately 81 in the United States. The major concern of this benign disease is that in making the diagnosis the patients undergo the risk of surgery because of the presumed preoperative diagnosis of cancer. Greater awareness of this disease is needed as the geographic distribution of human pulmonary dirofilariasis expands in this country.

Human dirofilariasis with reactive arthritis--case report and review of the literature

A 43-year-old German man suffered from an insect bite, which was followed by a severe local inflammation and lymphadenitis. A year later, he developed dry cough, chest pain, and an oligoarthritis of the ankle and knee joints. While other causes of the symptoms could be excluded, serologic findings suggested a dirofilarial infection with reactive arthritis due to the parasite. The observation points out, that in cases of unclassifiable mono- or oligoarthritis, reactive arthritis due to parasites should be considered in the spectrum of differential diagnoses. The disease is rare at present, but its frequency might be underestimated because of the diagnostic difficulties. Dirofilarial infection should be borne in mind after a stay abroad. The present case, however, shows, that the disease also occurs in patients who had not travelled to regions of risk in recent years.

Serologic diagnosis of zoonotic pulmonary dirofilariasis

Four symptomatic and four asymptomatic patients with histologically confirmed zoonotic pulmonary dirofilariasis caused by Dirofilaria immitis (dog heartworm) were evaluated serologically. Five patients had diagnostic indirect hemagglutination titers to D. immitis and six had positive findings by enzyme-linked immunosorbent assay. Of the two patients that had nondiagnostic titers by both enzyme-linked immunosorbent assay and indirect hemagglutination, one had an encapsulated necrotic adult worm that appeared to have been dead for some time, and the serum specimen for the second patient had been obtained five months following surgical removal of the granuloma. These findings suggest good sensitivity for these serologic methods in active cases, but declining antibody titers and decreased sensitivity following worm death. In general, cross-reactivity of the enzyme-linked immunosorbent assay with serum from patients with other nonfilarial parasitic infections or neoplasms was not observed.