Lung - nontumor
Dirofilaria immitis

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 24 February 2017, last major update September 2011

Copyright: (c) 2003-2017,, Inc.

PubMed search: Dirofilaria immitis [title] pulmonary

Cite this page: Dirofilaria immitis. website. Accessed December 14th, 2018.
Clinical features
  • Dog heartworm; may infect humans as secondary end stage host, particularly in southern coastal states in US
  • Adult worms die in right ventricle, embolize in pulmonary arterial circulation
  • Embolization of dead worms may be clinically silent or cause chest pain, fever, chills, hemoptysis or blood eosinophilia
  • Evokes necrotizing granulomatous response with vasculitis in lung tissue
  • Rarely see dead worms
  • Usually self limited in humans, but may cause lung infarct
  • Usually diagnosed after resection of a nodule to exclude malignancy
  • Chest Xray: solitary peripheral pulmonary nodule or coin lesion (Int J Immunopathol Pharmacol 2010;23:345)
Case reports
Microscopic (histologic) description
  • Rounded infarct with coagulative necrosis, well demarcated from surrounding normal lung by epithelioid histiocytes and fibrous connective tissue
  • Focal calcifications and lymphoid aggregates
  • Necrotic nematode has homogenous cuticle without external ridges
  • Longitudinal muscle layer just internal to cuticle and internal cuticular ridges
Microscopic (histologic) images

Images hosted on other servers:

H&E and Movat stain

Contributed by Dr. Vladimir Zaitsev, Russia:

Pulmonary embolization

Pulmonary embolization