title: Pulmonary necrotizing granulomas of unknown cause: clinical and pathologic analysis of 131 patients with completely resected nodules.
abstract: BACKGROUND
  The cause of pulmonary necrotizing granulomas is often unclear, even after histologic examination. Our aim was to determine the clinical significance of histologically unexplained necrotizing granulomas.
  
  
  METHODS
  Pulmonary necrotizing granulomas surgically resected at the Mayo Clinic (1994-2004) were retrieved and reviewed retrospectively. Cases in which a cause was evident at the time of initial histologic examination were excluded. The analysis cohort comprised 131 completely resected histologically unexplained pulmonary necrotizing granulomas. Clinical and laboratory information was abstracted from medical records, chest CT scans were reviewed, histologic slides were reexamined, and additional ancillary studies were performed in selected cases.
  
  
  RESULTS
  A cause was determined on review in more than one-half of the histologically unexplained necrotizing granulomas (79 of 131, 60%) by reexamining histologic slides (47), incorporating the results of cultures (26), fungal serologies (14), and other laboratory studies (eight), and correlating histologic findings with clinical and radiologic information (13). Infections accounted for the majority (64 of 79), the most common being histoplasmosis (37) and nontuberculous mycobacterial infections (18). Noninfectious diagnoses (15 of 79) were rheumatoid nodule (five), granulomatosis with polyangiitis (Wegener) (five), sarcoidosis (four), and chronic granulomatous disease (one). Many cases remained unexplained even after extensive review (52 of 131, 40%). Most of these patients received no medical therapy and did not progress clinically or develop new nodules (median follow-up, 84 months).
  
  
  CONCLUSIONS
  A cause, the most common being infection, can be established in many surgically resected pulmonary necrotizing granulomas that appear unexplained at the time of initial histologic diagnosis. Patients whose granulomas remain unexplained after a rigorous review have a favorable outcome. Most do not develop new nodules or progress clinically, even without medical therapy.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN. Electronic address: mukhops@ccf.org.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Mukhopadhyay
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN.
authors.forename: Bradley E
authors.initials: BE
authors.lastname: Wilcox
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Myers
authors.affiliation: Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN.
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Bryant
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Seanne P
authors.initials: SP
authors.lastname: Buckwalter
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Wengenack
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Eunhee S
authors.initials: ES
authors.lastname: Yi
authors.affiliation: Department of Radiology, Section of Thoracic Radiology, Mayo Clinic, Rochester, MN.
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Aughenbaugh
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Specks
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Aubry
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006099:Granuloma / Q000473:pathology* / Q000601:surgery; D006801:Humans; D008171:Lung Diseases / Q000473:pathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009336:Necrosis / Q000473:pathology / Q000601:surgery; D011013:Pneumonectomy / Q000379:methods*; D011379:Prognosis; D012189:Retrospective Studies; D055815:Young Adult