Pseudotumour of the lung caused by Mycobacterium malmoense infection in an HIV positive patient

Mycobacterium Spindle Cell Pseudotumor Caused by Mycobacterium xenopi: A First Described Association of a Rare Entity Presenting in the Lung

Mycobacterial spindle cell pseudotumor (MSP) is a rare benign lesion characterized by a proliferation of bland spindle-shaped histiocytes with vague granulomatous formation, positive for acid-fast bacilli staining. This lesion is usually reported in the lymph nodes and skin of immunocompromised patients; only 6 cases primary in the lung have been reported in the English literature to this date. In this article, we present the case of a 42-year-old female status post failed kidney-pancreas transplant with subsequent multiple kidney transplants, on chronic immunosuppression, who developed a mass in the left lower lobe consistent with MSP. Mycobacterium xenopi was identified in lung tissue culture, an association never previously described in literature. This case report alerts for the possible association of this rare form of non-tuberculous mycobacteria in the pathogenesis of MSP and highlights the importance of this differential diagnosis in lung masses of immunocompromised patients.

Pulmonary Mycobacterial Spindle Cell Pseudotumor: A Report of 3 Cases Including a Practical Approach to Histopathologic Recognition of This Unusual Entity

Mycobacterial spindle cell pseudotumor (MSP) is a rare benign spindle cell lesion containing acid-fact mycobacteria. These lesions are most commonly identified in the lymph nodes, skin, spleen, or bone marrow of immunocompromised patients and only rarely involve the lungs. We report 3 cases of pulmonary MSP, which include 2 patients who are known to be HIV-positive. The histopathological diagnosis of MSP in the lung lends itself to many challenges due to its rare incidence and its spindled tumor-like appearance. The differential diagnosis is broad and includes both benign and malignant entities. We highlight the importance of the clinical context in which these lesions typically present and the morphologic spectrum of features seen, and we offer a practical approach to the workup of pulmonary mycobacterial pseudotumor. Appropriate recognition of this entity should lead to an accurate diagnosis of a treatable benign condition despite the clinical presentation often favoring malignancy.

Pulmonary histoplasmosis producing a spindle cell "pseudotumor"

Pulmonary spindle cell proliferations have been reported in association with a limited group of infectious agents. These lesions are rare and identified most often in the setting of immunosuppression. Because their appearance can simulate a spindle cell neoplasm, they are diagnostically treacherous, sometimes delaying antimicrobial therapy or resulting in unnecessary surgery. We report a case of a spindle pseudotumor of the lung resulting from Histoplasma capsulatum infection, a previously unreported cause of a spindle cell lesion in the lung. The patient was a 67-year-old woman in whom positron emission tomography-positive nodules developed in the left lung and left mediastinum. The patient had undergone renal transplantation and was receiving immunosuppressive therapy with mycophenolate, tacrolimus, and low-dose prednisone. Infection with H capsulatum was confirmed by culture of pleural effusion fluid, DNA probe analysis of the pleural fluid culture isolate, urinary Histoplasma antigen detection, and Grocott methenamine silver stains of tissue sections. To our knowledge, this is the first case of a spindle cell "pseudotumor" of the lung resulting from histoplasmosis. It highlights the importance of performing special stains for organisms when evaluating pulmonary spindle cell lesions in an immunocompromised host.

Pseudotumor of the tracheal-laryngeal junction with unusual morphologic features caused by Rhodococcus equi infection

Infectious pseudotumors are unusual proliferations of histiocytes in response to certain microbial organisms. Occasionally this process may involve large airways, producing a mass lesion that may cause respiratory obstruction. Infectious pseudotumors can be confused with malignancy in their radiologic appearance and clinical presentation. We present a case of an aggressive endotracheal pseudotumor associated with Rhodococcus equi infection in a patient with advanced HIV disease. Microscopically, the lesion was composed of sheets of epithelioid histiocytes with large, strongly eosinophilic intra-cytoplasmic granules and features of malakoplakia. In this report, we review the literature of these unusual lesions and compare them to cases of conventional malakoplakia involving the large airways. We also explore the pathogenetic mechanisms that may contribute to the distinctive histologic appearance of Rhodococcus-associated pseudotumors.

Cryptococcal Inflammatory Pseudotumors

"Inflammatory pseudotumors" (IPTs) embrace a heterogeneous spectrum of reactive, infective, and neoplastic entities, that are characterized by a clinical mass composed of a histologic proliferation of spindle cells in a background of inflammatory cells and collagen fibers. Although a spectrum of microorganisms have been identified in infective IPTs, mycobacterial infective IPTs are reported most commonly. We document 5 solitary cryptococcal IPTs, in 2 males and 3 females, aged 19 to 43 years, in the soft tissues of the anterior chest wall, thigh, and arm. All were HIV-positive and had been treated for disseminated cutaneous and/or meningeal cryptococcosis with antifungal therapy, 6 to 12 months earlier. The specimens demonstrated a storiform arrangement of plump spindle cells, in addition to spindle and polygonal cells that were arranged in a haphazard manner. Background lymphocytes, plasma cells, and fibrosis were noted, in addition to scattered giant cells and focal necrosis. On high-power examination, Cryptococcus neoformans yeasts were identified within and between vacuolated spindle and polygonal cells on routine and special stains, confirming cryptococcal IPTs. Immunophenotyping of the spindle cells confirmed a mixed histiocytic and myofibroblastic lineage, with a predominance of the former. In documenting 5, hitherto unreported, pseudotumoral spindle cell reactions to C. neoformans, we not only highlight the need for intense appraisal of all IPTs for infective agents on routine and special stains and investigations, but also postulate that a complex host-fungus interaction, coupled with an exuberant, myofibroblastic response to incomplete therapy, are the pathogenetic drive for the pseudotumoral presentation.

Plasma cell granuloma associated with pulmonary actinomycosis: a case report

Plasma cell granuloma (PCG) of the lung is a rare disease that usually presents as a pulmonary nodule or mass on incidental radiographic examination without symptoms. Although the etiology of PCG is still controversial, many findings have lent support to the lesion being a reactive inflammatory process rather than a neoplastic one. We describe a 53-yr-old male who presented with a hemoptysis and have a lung mass at the left upper lobe on chest radiograph. The lung mass was primarily diagnosed as PCG by percutaneous needle aspiration and biopsy, and the patient was treated with oral steroid because he and relatives refused the operation. However, the size of the lung mass did not change and open thoracotomy and lobectomy were done therefore. He was confirmed as having pulmonary actinomycosis with PCG after surgery. To our knowledge, this is the first report of PCG associated with actinomycosis in Korea.

Mycobacterium malmoense in Italy: the modern Norman invasion?

The isolation of Mycobacterium malmoense has for a long time been restricted to few countries of Northern Europe; reports from countries other than Sweden, Great Britain and Finland are rare and the first Italian case report has been published in 1995. Since 1988, however, fifteen strains of M. malmoense have been isolated in Italy, eleven of which in the last two years; of these, ten appeared clinically significant on the basis of medical records. The susceptibility of the strains and the role of high performance liquid chromatography of cell wall mycolic acids for a reliable identification are discussed.

[Diagnostic and therapeutic approach to plasma cell granuloma of the lung. Apropos of a case of favourable course under antibiotics]

Plasma cell granulomas are more often solitary benign tumoral lesions, which need early surgery both for diagnostic and therapeutic reasons. The authors report a case of multiple plasma cell granuloma, diagnosed on biopsies obtained by thoracoscopy, and with a good response to a long-term antibiotic treatment. A review of the literature shows that this behaviour may represent an interesting alternative to systematical surgery in some cases.

Mycobacterium malmoense bacteremia in two AIDS patients

We report two cases of Mycobacterium malmoense bacteremia in two patients with AIDS. These are the first reported cases of disseminated M. malmoense in human immunodeficiency virus patients occurring in the United States. This slow-growing organism can cause invasive disease mimicking Mycobacterium avium complex infection; recognition and identification of this organism by mycobacteriology laboratories are essential for appropriate diagnosis and therapy of disseminated disease.