Inflammatory myofibroblastic tumor, also called “inflammatory pseudotumor” or “plasma cell granuloma,” is the most common primary tumor of the lungs in children. It may occur within the parenchyma or as an obstructive endobronchial lesion. As in adults, these tumors are composed of spindled cells admixed with scattered inflammatory cells, including lymphocytes, plasma cells, and rare eosinophils. Hypocellular zones may be seen.

Congenital peribronchial myofibroblastic tumor, also described in the early literature as “congenital bronchopulmonary fibrosarcoma” and “congenital leiomyosarcoma,” is a rare myofibroblastic tumor of neonates formed by intersecting broad bands of bland spindled cells, vaguely subdividing the lung parenchyma along the connective tissue planes of the pleura, interlobular septa, and peribronchial regions. Malformed cartilage plates are interspersed with the spindle-cell proliferation in the peribronchial regions.

Myofibromatosis refers to multifocal myofibroblastic lesions, typically diagnosed in infants and young children. In addition to skin and soft-tissue distribution, visceral involvement may occur. Multiple lesions in the lung may mimic metastatic tumor.

The tracheobronchial tree is the most common site of extra-appendiceal carcinoid tumors in children. Bronchial carcinoid tumors are considered to be low-grade neuroendocrine tumors, and although most behave in a benign fashion, recurrence or metastasis may occur.