The surgical pathology of pulmonary infarcts: diagnostic confusion with granulomatous disease, vasculitis, and neoplasia

Abstract

Twenty-three cases of surgically resected pulmonary infarcts sent in consultation were reviewed to evaluate their morphology and to assess reasons for consultation. The morphology of these infarcts demonstrated that only a minority had the classical triangular shape at low magnification (26%) whereas the majority were either spherical (17%) or had a geographic pattern of necrosis (35%). The margin of the infarcted tissue often had a pseudogranulomatous appearance due to palisaded histiocytes, foam cells, or perpendicularly oriented proliferations of fibroblasts and myofibroblasts (74%) and occasional cholesterol-and hemosiderin-laden giant cells. Basophilic granular karyorrhectic necrosis was seen focally (52%) as was vascular inflammation (56%) raising the differential diagnosis of Wegener's granulomatosis or infectious granulomas. These nonclassical features combined with a low incidence of clinical hemoptysis, chest pain and pleurisy, and a primary radiographic diagnosis of 'nodule r/o malignancy' highlight the need to consider thromboembolic pulmonary infarcts in the differential diagnosis of necrotic lung nodules with a histiocytic and fibroproliferative rim. Keywords: infarct; thromboemboli; lung Discussions of pulmonary thromboemboli and pulmonary infarcts most often occur in the autopsy suite rather than the surgical pathology laboratory. In fact, some renowned textbooks on pulmonary surgical pathology have failed to discuss the pathology of thromboemboli or infarcts at all, leaving such descriptions to basic pathology textbooks such as Robbins. 1 We have recently encountered a number of pulmonary infarcts that have been resected surgically, often to exclude neoplasia, which have proven diagnostically problematic to surgical pathologists who have referred them as granulomatous disease, vasculitis, and neoplasia. This precipitated a review of our files and a histologic study of surgically resected thromboembolic pulmonary infarcts to highlight their morphologic spectrum including variations from classical descriptions. Materials and methodsSeventy-eight cases of pulmonary infarcts were retrieved from the consultation files and the surgical pathology archives of the University of Pittsburgh Medical Center between 1994 and 2008. Of these 23 cases were specifically selected as being a result of thromboembolic disease rather than other causes of pulmonary infarction, including neoplasia, infection, vasculitis, amyloid, intravascular foreign bodies, septic infarcts, diffuse alveolar damage, torsion, and amniotic fluid emboli; 10 were reviewed within the last 2 years. Only wedge/ segmental biopsies of the lung were reviewed; four core biopsies of thromboembolic pulmonary infarcts were excluded from consideration.From 6 to 34 (mean 6) hematoxylin and eosin stain slides were available for review from each case. Ziehl-Nielsen and Gomori methenamine silver stains were reviewed and interpreted as negative in all cases. Verhoeff-van Gieson elastic tissue stains were carried out in 18 cases. Relevant clinical and radi...

The rim sign: FDG-PET/CT pattern of pulmonary infarction

“…This metabolic pattern is consistent with pathologic data on pulmonary infarction, showing that consolidation in pulmonary infarction is mainly caused by central blood alveolar filling with a peripheral inflammatory reaction including a foamy macrophage margin at the edge of central necrosis [10]. FDG uptake is certainly related to this inflammatory peripheral process.…”

Reversed halo sign in acute pulmonary embolism and infarction

“…In their 1940 paper on pulmonary infarction, Hampton and Castleman correlated postmortem findings and the changes in antemortem and postmortem radiographs and noted that none of the infarcts were pyramidal in shape or truly triangular (5). In a more recent pathological study of 23 surgical specimens of pulmonary infarcts, only six (26%) were triangular or wedge-shaped (7). Furthermore, a radiologic-pathologic correlative study of postmortem lung specimens utilizing CT found that peripheral wedge-shaped opacities were not specific for infarction (8).…”

Necrotizing granulomatous inflammation: what does it mean if your special stains are negative?

“…As infectious necrotizing granulomas may exhibit coagulative type necrosis, another important differential diagnosis is arterial infarct (Figure 6), particularly in a small biopsy specimen where sampling may be an issue. 5 Furthermore, infarcts as they organize may be surrounded by a rim of fibroblasts and inflammatory cells which can mimic granulomatous inflammation and described as 'pseudo granulomatous'. In a study of wedge resection specimens, arterial thrombosis was seen in all cases of infarcts, a feature that would distinguish infarct from infectious necrotizing granuloma.…”

“…In a study of wedge resection specimens, arterial thrombosis was seen in all cases of infarcts, a feature that would distinguish infarct from infectious necrotizing granuloma. 5 In summary, there is often no single histological feature that distinguishes infectious necrotizing granulomas from other specific disorder, with the exception of true necrotizing vasculitis that, in the context of necrotizing granulomas, would support the diagnosis of WG. It is the combination of multiple features, which can lead the pathologist towards a specific diagnosis.…”