A 30-year-old man with recurrent pneumonia. (Pathologic Quiz Case).
[FIGURES 1-2 OMITTED]
Grossly, the specimen measured 19.0 x 11.5 x 4.5 cm and weighed 350 g (Figure 3). On cross-section, a solid, noncrepitant, ill-defined, tan-white mass encased by a fibrous rim (arrow) measuring up to 5.5 cm in greatest dimension was identified. Several dilated bronchioles filled with purulent material were evident. Microscopically, the lesion revealed dense chronic inflammatory infiltrates, predominantly lymphocytes and lymphoid aggregates with germinal centers, and fibrosis that distorted or obliterated the normal architecture (Figure 4). Several bronchial structures lined by normal-appearing respiratory epithelium are seen filled with purulent material. Much of the involved tissue had undergone solidification, with florid interstitial proliferation including myxoid change. Marked vascular changes, ranging from thickening of arterial walls to near obliteration of the entire luminal space, were noted. Granulomatous configurations with a curious paracrystalline material in the core surrounded by epithelioid giant cells were also identified. Acid-fast, fungus, mucin, and periodic acid-Schiff stains with adequate controls failed to reveal micro-organisms. No evidence of pleura was seen in any section.
[FIGURES 3-4 OMITTED]
What is your diagnosis?
Pathologic Diagnosis: Intralobar Bronchopulmonary Sequestration
A bronchopulmonary sequestration represents an abnormal, nonfunctioning mass of lung tissue that lacks a connection to the tracheobronchial tree and that is supplied by a systemic artery. (1) Sequestrations represent between 0.15% and 6.45% of all bronchopulmonary malformations. (2) They are divided into extralobar sequestrations (ELS) and intralobar sequestrations (ILS). Extralobar sequestrations are enveloped by an independent pleural covering and may be located anywhere in the thorax or abdomen. (1,3,4) Eighty-three percent are found in the left thorax, and approximately 77% are found between the diaphragm and the lower lobe. (1,3) Intralobar sequestrations, in contrast, lack a pleural covering and are contained within otherwise normal lung parenchyma. (3,4) Ninety-eight percent are found within the lower lobes, and roughly 60% occur in the left lung. (1,3,4) The embryogenesis of a sequestration is somewhat controversial. Some authorities hold that both ELS and ILS represent abnormal buds of pluripotent embryonic tissue that become isolated from the primitive foregut. (1,3,4) For example, traction from an aberrant systemic artery may provoke the sequestration by inducing interstitial fibrosis. (4) Extralobar sequestrations remain separate from the normally developing lung, whereas ILS become enveloped in it. (1,3,4) Intralobar sequestrations, however, may represent an acquired condition. (4) Following recurrent localized infection in a previously normal portion of lung, the damaged area becomes amputated from the normal lung and encapsulated by fibrosis and chronic inflammatory infiltrate. (4,5) Neovascularization into the resulting granulation tissue and parasitization, with subsequent hypertrophy of normally occurring small systemic arteries within the inferior pulmonary ligament, then establishes the independent circulation. (4,6) An acquired etiology is supported by the finding that ILS are virtually nonexistent in neonates and infants and are associated with congenital anomalies in only 6% to 12% of cases. (4) This discovery is in contrast to ELS, which are frequently found in neonates and are associated with other congenital anomalies such as pleuroperitoneal hernias and gastrointestinal fistulas in greater than 50% of cases. (1)
A small-caliber branch of the aorta is the typical arterial supply of an ELS. (1) Intralobar sequestrations, in contrast, are supplied by a large-caliber artery branching off the thoracic aorta in 73% of cases. (4,6) Branches of the abdominal aorta, intercostals, subclavian, innominate, internal thoracic, pericardiophrenic, gastric, celiac, suprarenal, and pulmonary arteries have also been documented. Intralobar sequestrations are then subdivided according to the amount of pulmonary arterial contribution into types I, II, and III if they posses extensive, slight, or absent pulmonary input, respectively. (3) Although they are of systemic origin, these vessels are invariably elastic arteries, like normal pulmonary arteries. (4) Elastic arteries are thought to be more fragile than muscular arteries, and therefore they pose an increased risk of hemorrhage during surgery. Venous drainage is through the normal pulmonary veins in 95% of cases, but connection to the azygous, hemiazygous, or superior vena cava has been documented. (4,5)
The clinical presentation of bronchopulmonary sequestrations is nonspecific. Extralobar sequestrations are frequently asymptomatic and are found incidentally. Infants, however, may present with respiratory distress resulting from associated diaphragmatic herniation or recurrent aspiration secondary to a gastrointestinal fistula. (2,6) Patients with ILS typically present in childhood, but approximately 50% present past the age of 20. (4) Signs of recurrent infection or pneumonia with productive cough, fever, and hemoptysis dominate. Chest pain, pleuritic pain, and asthma are also common. Intralobar sequestrations may rarely present in both infants and adults as cardiomegaly with or without congestive heart failure due to a left-to-left shunt. (1,4,7) Cardiac complications, though, tend to be more common in undiagnosed sequestrations and those with larger nutrient vessels. (7) Approximately 15% may be asymptomatic, however. Physical examination is equally nonspecific but may reveal dullness to percussion with some degree of decreased breath sounds in the involved area, cyanosis, clubbing of the fingers, or pectus excavatum. (1,3,4) A continuous or pansystolic murmur auscultated over the aberrant vessels may also be appreciated. (4)
Diagnosis is typically suggested by clinical history. Chest radiograph usually reveals a homogeneous consolidation with irregular margins or a uniformly dense mass with variable contours. (4) Air-fluid levels and cavitation may be present depending on the degree of cystic formation. Angiography, particularly aortography, is necessary to delineate the vascular supply, and it essentially confirms the diagnosis. (4,6) Differential diagnosis based upon clinical and radiographic presentation includes neurogenic tumors, lateral thoracic meningocele, extramedullary hematopoiesis, pleural tumor, pulmonary abscess, necrotizing pneumonia, mycobacterial or fungal pneumonia, cavitating neoplasm, empyema, bronchiectasis, emphysema, bronchogenic and foregut cysts, and cystic adenomatoid malformation. Histologically, ELS recapitulates normal lung architecture but with widespread structural dilatation. (4) Intralobar sequestrations, however, are typified by dense fibrosis and intense chronic inflammatory infiltrate including lymphocytes and lymphoid aggregates with germinal centers. Furthermore, marked vascular changes including thrombosis, endarteritis, medial hypertrophy, and advanced atherosclerosis are common. (3,4) Cysts are lined by cuboidal or columnar epithelium and are filled with eosinophilic debris or foamy macrophages. (4) Sequestrations have been documented to harbor squamous cell carcinoma and adenocarcinoma, tubercular infection, and various fungal infections. (4) Massive hemoptysis also has been reported. Because of these and because of the additional risks of recurrent infection and cardiac complications, the treatment for ILS is surgical resection. (4,6) Prior to surgery, however, the supplying vessels must be carefully delineated to prevent the complication of catastrophic hemorrhage. Otherwise, mortality and morbidity are low, with hemothorax and fistula formation being the most frequent surgical complications, occurring in less than 1%. (1) Barring the presence of other congenital anomalies, then, the prognosis is excellent.
(1.) Bone RC, Campbell GD, Payne DK. Bone's Atlas of Pulmonary and Critical Care Medicine. New York, NY: Lippincott, Williams, and Wilkins; 1999.
(2.) Savic B, Birtel FJ, Tholen W, Funke HD, Knoche R. Lung sequestration: report of seven cases and review of 540 published cases. Thorax. 1979;34:96-101.
(3.) Rosai J. Ackerman's Surgical Pathology. 8th ed. St. Louis, Mo: The CV Mosby Co; 1996.
(4.) Frazier AA, Rosado de Christenson ML, Stocker JT, Templeton PA. Intralobar sequestration: radiologic-pathologic correlation. Radiographics. 1997;17:725-745.
(5.) Askin FB. Pulmonary disorders in the neonate, infant, and child. In: Thurlbeck WM, ed. Pathology of the Lung. New York, NY: Thiene Medical Publishers Inc; 1988:115-146.
(6.) Halkic N, Cuenoud PF, Corthesy ME, Ksontini R, Boumghar M. Pulmonary sequestration: a review of 26 cases. Eur J Cardiothorac Surg. 1998;14:127-133.
(7.) Fabre OH, Porte HL, Godart FR, Rey C, Wurtz AJ. Long-term cardiovascular consequences of undiagnosed intralobar pulmonary sequestration. Ann Thorac Surg. 1998;65:1144-1146.
Accepted for publication July 23, 2001.
From the Department of Pathology, Medical College of Ohio, Toledo, Ohio.
This manuscript was presented at the 20th Annual Peter J. Goldblatt, MD, Scientific Day, Toledo, Ohio, May 16, 2001.
Reprints not available from the author.
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|Title Annotation:||intralobar bronchopulmonary sequestration|
|Author:||Shope, Adam L.; Islam, Shahidul; Zaher, Aiman|
|Publication:||Archives of Pathology & Laboratory Medicine|
|Date:||May 1, 2002|
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