Coin lesion (lung)

A coin lesion refers to a round or oval, well-circumscribed solitary pulmonary lesion. It is usually 1-5 cm in diameter and calcification may or may not be present ^1,3. Typically but not always the patient is asymptomatic ¹. 

Differential diagnosis

The differential diagnosis for such lesions is  ^1-3:

• malignancy
  • primary lung malignancy
  • metastases
• infection
  • pulmonary tuberculosis
  • pneumonia, especially Streptococcus spp., Staphylococcus spp., or Klebisiella spp. infection
  • hydatid cyst
  • abscess
• benign disease processes
  • granulomatosis with polyangiitis
  • pulmonary hamartoma
  • pulmonary arteriovenous malformation
  • rheumatoid nodule
  • bronchogenic cyst
  • bronchial adenoma

Mimics

Not every round opacity projected over the lung is within the actual lung itself. Possible mimics include:

• external artifacts (eg. button on clothing, ECG dot)
• nipple shadow
• prominent first costal cartilage calcification 
• rib fracture with expansible callous or other sclerotic bone lesion
• pleural pseudotumor due to encysted pleural fluid
• summation of markings (eg. overlap of vessels and ribs)
• cutaneous lesion (e.g. cutaneous neurofibroma)

See also

• solitary pulmonary nodule