 As the lesion progresses, skin becomes adhered to the mass and may rupture, forming a sinus and an open wound.Diagnosis is usually performed by needle aspiration biopsy or excisional biopsy of the mass and the histological demonstration of stainable acid-fast bacteria in the case of infection by "M. tuberculosis" (Ziehl-Neelsen stain), or the culture of NTM using specific growth and staining techniques.The classical histologic pattern of scrofula features caseating granulomas with central acellular necrosis (caseous necrosis) surrounded by granulomatous inflammation with multinucleated giant cells.