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Pulmonary artery (intimal) sarcoma

Pulmonary artery intimal sarcoma is a rare malignant neoplasm that arises in the pulmonary arteries. It may involve the proximal elastic arteries anywhere from the level of the pulmonary valve to the lobar branches. As shown in Figure 1, these tumors can extensively involve the pulmonary arterial system. This case involved the main pulmonary artery at the level of the pulmonary valve and extended into the interlobar vessels and truncus anterior (see Figure 2 with corresponding low power histology [Figure 3]). The majority of the tumor often occupies the lumen of the affected pulmonary artery. However, the tumor can extend into perivascular soft tissue, which can be highlighted by an elastic histochemical stain (Figure 4). Pulmonary artery intimal sarcomas can have a variety of histologic patterns; the most common type is that of an undifferentiated pleomorphic sarcoma as seen in this case (Figure 5). Other important histologic types are a low-grade spindle cell sarcoma with myxoid background (myxofibrosarcoma) and heterologous differentiation such as osteosarcoma and chondrosarcoma. Less common histologic patterns include leiomyosarcoma, synovial sarcoma, rhabdomyosarcoma, and angiosarcoma. A rare histologic subtype is low-grade inflammatory myofibroblastic sarcoma which has relatively less cellularity, pleomorphism and mitotic activity. These tumors have a myofibroblastic appearance with so called “tissue culture-like growth” and have been reported to have a good prognosis. Given the rarity of this tumor there is a paucity of studies on the underlying molecular basis. The most common known abnormality is MDM2 amplification, which can be detected by immunohistochemistry or other cytogenetic or genomic-based techniques. MDM2 amplification often occurs in association with amplification of PDGFRA.

These tumors can occur in patients across a large age range and often present with dyspnea and findings in keeping with chronic thromboembolic disease that is resistant to treatment with anticoagulation. Some studies suggest that incidental pulmonary artery sarcomas can be identified in 1-4% of thromboendarterectomy specimens from patients with chronic thromboembolic disease. As in this case, there may be areas of hemorrhagic infarction downstream from the main lesion (Figure 6).

The clinical outcome of pulmonary artery intimal sarcomas largely depends on the ability to completely resect the tumor. The 3-year survival is 70% in resected cases but the median survival is less than 1 year for tumors that are incomplete resections or inoperable.

Take home message

Pulmonary artery intimal sarcoma is a rare malignant neoplasm of the pulmonary artery that can present as chronic thromboembolic disease and is most commonly classified as an undifferentiated pleomorphic sarcoma.

Bandyopadhyay D, Panchabhai TS, Bajaj NS, et al. Primary pulmonary artery sarcoma: a close associate of pulmonary embolism-20-year observational analysis. J Thorac Dis 2016;8:2592–601.

Bode-Lesniewska B, Zhao J, Speel EJ, et al. Gains of 12q13-14 and overexpression of mdm2 are frequent findings in intimal sarcomas of the pulmonary artery. Virchows Arch 2001;438:57–65.

Tavora F, Miettinen M, Fanburg-Smith J, et al. Pulmonary artery sarcoma: a histologic and follow-up study with emphasis on a subset of low-grade myofibroblastic sarcomas with a good long-term follow-up. Am J Surg Pathol 2008;32:1751–61.

Matthew J. Cecchini, MD, PhD, FRCPC
Assistant Professor of Pathology
Department of Pathology and Laboratory Medicine
Western University
London, Ontario, Canada

Keith Kwan MD, FRCPC
Associate Professor
Department of Pathology and Laboratory Medicine
Western University
London, Ontario, Canada