Mycobacterium avium complex presenting as an infected epidermal inclusion cyst of breast: a rare case report

Non-tuberculous mycobacteria (NTM), including Mycobacterium intracellulare, are opportunistic pathogens mostly affecting immunocompromised individuals. Cutaneous involvement is rare and can mimic other diseases. Epidermal inclusion cysts (EICs) are benign and uncommon in the breast. MAC infection within an EIC is extremely rare and complicates diagnosis.

A 21-year-old immunocompetent woman presented with a painful, progressively enlarging right breast mass over six months. Examination revealed an erythematous swelling with draining sinus. Imaging suggested an abscess or infected cyst. FNAC showed squamous cells and inflammation. Ziehl-Neelsen stain and Mycobacteria Growth Indicator Tube (MGIT) culture confirmed MAC. She received amikacin, moxifloxacin, clarithromycin, and linezolid for 12 months with full resolution.

This case illustrates an unusual MAC infection in a breast EIC in an immunocompetent patient and emphasizes the need for microbiological studies in persistent breast lesions for accurate diagnosis and treatment.