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

Abstract

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.

Nodal mycobacterial spindle cell pseudotumor: A diagnostic pitfall

“…The most common etiological agent is Mycobacterium avium complex, while Mycobacterium tuberculosis complex is the second most common organism. Other rare non-tubercular mycobacteria that have been reported to be associated with spindle cell pseudotumors include: M chelonae, [9] M microti, [10] M haemophilum, M simiae, [11] M kansasii, M gordonae, M xenopi, [12,13] M szulgai, [14] M genavense. [15] There are also rare case reports of Bacillus Calmette-Guérin induced MSP.…”

“…McGoldrick et al 2010 [10] 44M Lymph node (mediastinum) M. microti Steroid and azathioprine treated oral lichen planus Ilyas et al 2011 [45] 63M Nasal cavity MAC** Treated DLBCL☨ Yeh et al 2011 [9] 55M Skin M. chelonae Steroid treated scleroderma Alves et al 2012 [46] 28M Liver MTB*** AIDS Philip et al 2012 [7] 51F Lung MAI* AIDS Sideras et al 2013 [47] 42M Plantar fascia No culture HIV Ohara et al 2013 [6] 83M Nasal cavity MAI* HIV (Table 1 continued on page 37.) Rahmani et al 2013 [4] 79M Skin MAC** Solid organ transplant, Immunosuppressive therapy Holmes et al 2014 [48] 58M Skin M. chelonae None Ismail et al 2015 [49] 69M Brain MAI* Steroid treated sarcoidosis Franco et al 2015 [50] 69F Lung MAC** Solid organ transplant (lung), immunosuppressive therapy Lim et al 2016 [51] 66M Brain MAC** Steroid treated sarcoidosis Coelho et al 2017 [15] 13M Lymph node M. genavense Stem cell transplant, immunosuppressive therapy Thwaites et al 2018 [52] 88M Bone M. chelonae Diabetes Fonda-pascual et al 2018 [53] 50M Skin (penis) MAI* Combined immunodeficiency Dhibar et al 2018 [54] 38M Lymph node MTB*** AIDS Boylan et al 2018 [55] 33M Lung No culture AIDS Boylan et al 2018 [55] 45M Lung MAC** HIV Boylan et al 2018 [55] 69F Lung No culture None Taneja et al 2020 [56] 34M Lymph node MAC** AIDS Furlan et al 2020 [13] 42F Mycobacterial pseudotumors not only cause clinical and diagnostic confusion but can also confound the clinical picture as seen in the second case. This case showed hepatic diffuse large B-cell lymphoma as well as nodal MSP.…”