Correct!
1. Intralobar pulmonary sequestration

The CT demonstrates a mass at the medial left lung base, previously infected, with a large vessel emanating from the thoracic aorta supplying the mass (Figure 4).

Figure 4. Two large, anomalous vessels originating from the descending thoracic aorta (arrows) are seen entering the lesion (arrowheads).

In a young adult a history of recurrent infection in this region is characteristic of intralobar sequestration. Pleuropulmonary blastoma is a very rare primary thoracic tumor that may be primarily solid or cystic, associated with a poor prognosis, but typically affects very young children (frequently under the age of 6). These lesions manifest on imaging as large masses, occasionally associated with pneumothorax. Primary pulmonary lymphoma is a relatively uncommon diagnosis that may manifest with a wide variety of patterns, including single or multiple nodules or masses, peribronchial nodules, lymphadenopathy, pleural abnormalities, etc. While primary pulmonary lymphoma could manifest as a medial lung mass, the intense vascularity of the lesion, derived from the large, anomalous feeding vessel arising from the descending thoracic aorta, is not a feature usually associated with this disorder. Primary pulmonary sarcomas are very rare lesions. Sarcomas may affect a number of structures in the thorax, including the heart (angiosarcoma), pulmonary artery (leiomyosarcoma and a number of other histopathological subtypes), and the chest wall (numerous patterns of histopathological differentiation). Sarcomas may also arise within the mediastinum, lung, and pleura- the imaging features of these neoplasms is generally non-specific, but a large, inhomogeneous lesion with an aggressive appearance would be expected; the vascular supply derived from the descending thoracic aorta is not a feature of primary pulmonary sarcomas. Splenosis results from autotransplantation of splenic tissue into ectopic locations, usually as a result of trauma to the spleen. The typical imaging appearance of splenosis consists of mesenteric, peritoneal, and omental nodules but occasionally splenic tissue may gain access to the thorax through traumatic diaphragmatic rupture or through various foramina that traverse the diaphragm. In this circumstance, the ectopic splenic tissue presents as one or more nodules related to the pleura, typically left-sided. The ectopic splenic tissue often enhances intensely, as normal splenic tissue does. Often a history of trauma is present, and the absence of the normal spleen in the left upper quadrant may be evident on thoracic CT.

Diagnosis: Left lower lobe intralobar pulmonary sequestration

Which of the following regarding pulmonary sequestration is false?

1. Intralobar sequestrations are more commonly encountered in adults, whereas extralobar sequestrations are more commonly found in infants and very young children
2. Both intralobar and extralobar sequestrations typically derive their blood supply from the thoracoabdominal aorta
3. Intralobar sequestrations typically drain into the systemic venous circulation to the right atrium, whereas extralobar sequestrations typically drain into the pulmonary venous circulation to the left atrium
4. Extralobar sequestrations are contained within their own visceral pleural lining, whereas intralobar sequestrations share the visceral pleural lining of the otherwise normal lung
5. Intralobar sequestrations often present as recurrent infections in young adults, whereas extralobar sequestrations are more commonly encountered as uninfected masses in infants and young children, occasionally associated with congenital anomalies.

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