Pseudotumor of the Tracheal-Laryngeal Junction with Unusual Morphologic Features Caused by Rhodococcus equi Infection

Abstract

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.

Malakoplakia of Larynx: A Case Report and Literature Review of Localized Malakoplakia of Larynx

“…With the results of previous case reports of laryngeal malakoplakia, single surgery had achieved good results in a short time follow-up, of course, except for patients with immunodeficiency. 26 Our case had shown a satisfactory curative effect. In this case, malakoplakia recurrence was not found in a one-year follow-up.…”

Pleural empyema with endobronchial mass due to Rhodococcus equi infection after renal transplantation: A case report and review of literature

“…Of note, when our patient underwent fiberoptic bronchoscopy, a nascent mass was found at the mouth of the middle and lower lobes of the right lung, which was diagnosed as an inflammatory granulomatous hyperplasia on histopathologic biopsy. We hypothesized that the endobronchial mass was associated with R. equi infection, which has been previously reported as an associated endobronchial mass in addition to pulmonary manifestations in HIV patients infected with R. equi [ 10 - 12 ]. To our knowledge, this is the first reported case about a renal transplant recipient who developed pleural empyema combined with endobronchial mass after infection with R. equi .…”

Infectious Pseudotumors: Red Herrings in Head and Neck Pathology

“…Cultures, serologic studies, and PCR assays for Bartonella, Mycobacteria, Histoplasma and Blastomyces were all negative. The patient was started on HAART therapy in addition to an antibiotic regimen including vancomycin, meropenem, and azithromycin, based on known susceptibility of R. equi [1].…”

“…As a result, the bacterium is able to survive and proliferate within an almost neutral phagolysosomal environment [4,5]. The high pH in these organelles may also explain their strong eosinophilia [1]. Some cases of R. equi pseudotumors show Michaelis-Gutmann bodies analogous to those that are diagnostic of malakoplakia [6] [ Fig.…”