Tuberculosis Causing a Pectoral Mass Mimicking Malignancy: A Rare Presentation of Tuberculosis.

Tuberculosis is an infectious disease that may involve all systems, with the respiratory system being the most commonly affected. Tuberculosis of the chest wall and its structures is rare, in which malignancy and abscess may be counted among possible differential diagnoses. In this case report, a patient with pectoral muscle tuberculosis will be presented. A 47-year-old female with a history of hypertension and epilepsy was evaluated for a rapidly enlarging painful mass under the left breast, which was later considered a cold abscess. The routine laboratory tests showed elevated C-reactive protein and erythrocyte sedimentation rate. Further radiological imaging with computed tomography confirmed the mass with chest wall involvement. The performed biopsy revealed granulomatous inflammation and subsequent tests confirmed acid-fast bacteria, with later confirmation of Mycobacterium tuberculosis in the culture. The patient was treated with an intensive regimen of anti-tuberculosis (TB) drugs consisting of isoniazid, rifampin, pyrazinamide, and ethambutol. After nine months, including a treatment extension due to possible vertebral involvement, the patient showed no symptoms and is under follow-up. Extrapulmonary TB, particularly musculoskeletal TB, comes with many diagnostic challenges due to its nonspecific symptoms. Tissue sampling remains the most important aspect of diagnosis confirmation and treatment planning; hence, TB should always be kept in mind among possible differential diagnoses, especially in endemic regions.