Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Pulmonary Inflammatory Pseudotumor
- Radiologic Findings
- CT shows an endobronchial polypoid mass in the posterior basal segmental bronchus of right lower lobe, which is enhanced after contrast administration. Mucoid impaction of subsegmental bronchi of the posterior basal segment is associated with the lesion.
- Brief Review
- Inflammatory pseudotumor is a quasineoplastic lesion consisting of inflammatory cells and myofibroblastic spindle cells. Inflammatory pseudotumor most commonly involves the lung and the orbit, but it has been reported to occur in nearly every site in the body, from the central nervous system to the gastrointestinal tract.
Inflammatory pseudotumor is the most common primary lung mass seen in children, constituting approximately 50% of benign intrapulmonary tumors seen in pediatric patients. These tumors have no sex predilection, and their peak prevalence is in the second decade of life. Cough, fever, dyspnea, and hemoptysis are the usual presenting symptoms.
On the basis of the predominant histopathologic features, the lesions can be divided into three histologic types: (a) organizing pneumonia pattern, characterized by airways filled with plump fibroblasts and foamy histiocytes and parenchyma replaced with a mixture of histiocytes, mononuclear cells, and fibroblasts; (b) fibrous histiocytic pattern, which is the most common, and is characterized by spindle-shaped myofibroblasts arranged in whorls; and (c) lymphohistiocytic pattern, which is the least common and is characterized by a mixture of lymphocytes and plasma cells with only minimal fibrous connective tissue.
On radiographs, inflammatory pseudotumor typically appears as a solitary, peripheral, sharply circumscribed, lobulated mass with an anatomic bias for the lower lobes. On CT scans, inflammatory pseudotumors have a variable and nonspecific appearance, but most commonly they appear with heterogeneous attenuation and enhancement. Calcification within the lesion occurs more frequently in children than in adults. The calcification pattern ranges from an amorphous, mixed, or fine fleck-like pattern to heavy mineralization. Cavitation and lymphadenopathy are rare. Atelectasis and pleural effusion may occur.
When inflammatory pseudotumor are endobronchial in location, they are typically polypoid and may or may not extend beyond the bronchial wall. Endoluminal airway involvement has been known to occur in 10-12% in previous reports. Recently Kim et al. observed that 5 (50%) of 10 patients with inflammatory pseudotumor had major airway involvement. They concluded that inflammatory pseudotumor should be included in the differential diagnosis when a well-defined, polypoid, endotracheal/endobronchial nodule is seen on CT.
The radiologic differential diagnosis for inflammatory pseudotumor occurring as a solitary pulmonary nodule includes primary or secondary neoplasm, hamartoma, chondroma, hemangioma, granuloma, and pulmonary sequestration. Inflammatory pseudotumor may resemble pulmonary intralobar sequestration in that its blood supply is derived from the systemic arteries. As a endobronchial tumor, inflammatory pseudotumor should be included in differential diagnosis with squamous cell carcinoma, adenoid cystic carcinoma, mucoepidermoid carcinoma, carcinoid tumor, leiomyoma, neurogenic tumor, and hamartoma.
- References
- 1. Kim TS, Han J, Kim GY, Lee KS, Kim H, Kim J. Pulmonary inflammatory pseudotumor (inflammatory myofibroblastic tumor): CT features with pathologic correlation. J Comput Assist Tomogr 2005;29 :633-639.
2. Hedlund GL, Navoy JF, Galliani CA, Johnson WH. Aggressive manifestations of inflammatory pulmonary pseudotumor in children. Pediatr Radiol 1999; 29:112?16.
3. Agrons GA, Rosado-de-Christenson ML, Kirejczyk WM, Conran RM, Stocker JT. Pulmonary inflammatory pseudotumor: radiologic features. Radiology 1998; 206:511?18.
4. Narla LD, Newman B, Spottswood SS, Narla S, Kolli R. Inflammatory pseudotumor. Radiographics. 2003; 719-729.
- Keywords
- Lung, Benign tumor, Pulmonary Inflammatory Pseudotumor