Crack cocaine pigment

A new cause of black lung and black lavage fluid is crack cocaine smoking. Here, alveolar macrophages are loaded with black pigment. Interstitial black pigment, however, should be attributed to other causes.

Mixed dust pneumoconiosis

Features include:

  • Peribronchiolar or pleural nodules with irregular (stellate) margins
  • Variable amounts of black pigment and some birefringent crystals
  • Little fibrosis
  • Cellularity--histiocytes, lymphocytes, plasma cells

Note the bronchiole and artery (upper right).

The mixed dust lesion is associated with exposure to silica and other dusts--coal dust, smoke from fires, and silicates--which modify its histologic effect on the lung. The mixed dust lesion is stellate, more cellular, and less fibrotic than the round, fibrotic, silicotic nodule, which results from inhalation of dust with a high content of silica.