| | Diagnosis | Tests to consider |
| | Sarcoidosis | ACE level, chest radiograph, and serum calcium | | Tuberculosis | PPD, MTB QuantiFERON Gold, chest radiograph, acid fast tissue stain, and mycobacterial tissue culture | | Infectious mastitis | Tissue culture for bacteria, fungi, and atypical mycobacteria; Gram stain, fungal stain, acid fast stain; fungal serologies if fungal infection suspected in endemic areas | | Wegener’s granulomatosis | ANCA antibody, PR3 antibody, CRP, creatinine, UA, and chest radiograph | | Giant cell arteritis | ESR/CRP | | Takayasu’s arteritis | ESR/CRP, CBC (may show anemia or elevated platelets), CT chest angiography with contrast, or CT abdomen angiography with contrast | | Churg–Strauss syndrome | CBC with differential to evaluate for eosinophilia, histopathology of affected organ, and electromyelogram to diagnosis peripheral neuropathy or mononeuritis multiplex | | Crohn’s disease | Colonoscopy with ileal exam, small bowel imaging with CT or MR enterography, evidence of extraintestinal signs (erythema nodosum, pyoderma gangrenosum, episcleritis, scleritis, anterior uveitis or iritis, and primary sclerosing cholangitis) | | IgG4-RD mastitis | Histopathology demonstrating classic findings; serum IgG4 levels not needed for diagnosis but can be supportive of diagnosis | | Diabetic mastopathy | Characteristic histopathology in a patient with type I diabetes | | Breast cancer | Histopathology, ideally from core needle biopsy |
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