Physical exam looking for characteristic triad (tumor, sinus tract, and macroscopic grains)
Microscopy of grains using 20% potassium hydroxide solution
Gram stain can be considered to evaluate for alternative diagnoses
Deep biopsy with culture
Imaging: CT or MRI (although MRI more sensitive) to determine bony involvement and extent of soft tissue involvement
PCR can be done to evaluate for specific causative pathogens
Eumycetoma
Actinomycosis
Giant cell tumor
Botryomycosis
Ganglion cyst
Nocardiosis
Basal cell carcinoma
Foreign body granuloma