Tissue PCR-detected musculoskeletal nontuberculous mycobacterial infection: Clinicopathologic features and granuloma formation.

BACKGROUND

Musculoskeletal nontuberculous mycobacterial (NTM) infection is an uncommon lesion that often poses substantial diagnostic difficulty because its clinical, radiologic, and histopathologic findings are nonspecific. This study investigated the clinicopathologic features of polymerase chain reaction (PCR)-detected musculoskeletal NTM infection, with particular emphasis on granuloma formation.

METHODS

We retrospectively reviewed 30 patients with musculoskeletal NTM infection detected by tissue PCR performed on surgically obtained specimens. Clinical, radiologic, histopathologic, treatment, and outcome data were analyzed, and factors associated with granuloma formation were assessed.

RESULTS

All cases had initially been interpreted as alternative neoplastic or infectious conditions before PCR confirmation. Granulomatous inflammation and necrosis were each identified in 20 of 30 cases (66.7%), although both findings co-occurred in only 14 cases (46.7%). Tissue acid-fast bacilli staining was positive in only one case (3.3%). Bone involvement was significantly associated with absence of granuloma (50.0% vs. 5.0%, p = 0.009). A tumor-like radiologic pattern, observed exclusively on magnetic resonance imaging (MRI), was also more frequent in granuloma-absent cases (40.0% vs. 5.6%, p = 0.041).

CONCLUSIONS

Musculoskeletal NTM infection shows variable histopathologic findings and frequently mimics other lesions. Bone involvement and tumor-like MRI findings may be associated with absence of granuloma, underscoring the diagnostic value of tissue PCR in histologically and clinicoradiologically challenging cases. Infectious disease specialist consultation was strongly associated with appropriate antibiotic administration, highlighting the importance of multidisciplinary involvement in treatment decision-making.