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25 June 2009 - Case #150

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This case was contributed by Dr. Keith Kaplan, Mayo Clinic, Minnesota (USA).

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Case #150

Clinical history:
A 37 year old woman presented with shortness of breath and abdominal pain consistent with cholecystitis. A cholecystectomy was planned but during her surgical workup, a pericardial mass was identified.

MRI (see below) showed a 12 x 12 x15-cm heterogeneous intrapericardial mass, which abutted the left ventricle and shifted the heart to the right. Portions of the mass also extended into the transverse sinus. Postcontrast images demonstrated avid arterial enhancement, as can be seen with sarcomas, particularly angiosarcoma. Small bilateral pleural effusions were present

The mass was excised.

Radiology images:

Gross images:

Microscopic images:





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Diagnosis: Synovial sarcoma of the pericardium





Synovial sarcoma usually affects the soft tissue of the joints and limbs. It can occur in the chest wall and lung but is extremely rare in the heart. It is associated with a t(X;18)(p11.2; q11.2) translocation in 90% of cases, leading to SSX1::SYT, SSX2::SYT or SSX4::SYT fusion genes (Clin Lung Cancer 2008;9:257, Mod Pathol 2002;15:679). Children and adults are equally affected but tumors may be more common in men in the heart (J Am Soc Endochardiogr 2007;20:197.e1).

Grossly, synovial sarcoma often presents as a bulky tumor that infiltrates the myocardium and pericardial surfaces. Histologically, it is biphasic with spindled and epithelioid cells or monophasic with only spindle cells. The spindle cell pattern is somewhat fascicular and has cellular and edematous areas. The spindle cells are small, compact and may be infiltrated by lymphocytes. The epithelioid areas, not prominent in this case, may form glands or nests and have lymphocytic infiltration. Although not obvious in this case, there is often a hemangiopericytoma-like vascular pattern (Am J Surg Pathol 2005;29:569). As in this case, the tumor is often positive for BCL2, CD99, pan-keratin and vimentin.

The differential diagnosis includes:
  • Mesothelioma: larger spindle cells with more pleomorphism, usually no infiltration of myocardium, no t(X;18) or fusion gene
  • Malignant peripheral nerve sheath tumor: 50% associated with neurofibromatosis, also associated with major nerve or continuous with neurofibroma; often palisading with monomorphic serpentine cells, geographic necrosis with tumor palisading at the edges, frequent mitotic figures, often bizarre tumor cells, usually CD99+, variable S100 (62%), CD57, p53
  • Fibrosarcoma: often left atrium, herringbone pattern of compact fibroblastic type cells with tapered nuclei in collagenous or myxoid matrix; no intracytoplasmic glycogen, no perinuclear vacuoles, no pleomorphism, no histiocytoid cells
  • Myxoma: tumor is dominated by myxoid matrix; also complex structures resembling cords, nests, rings or poorly formed glands, often surrounding blood vessels; composed of stellate or globular myxoma cells with abundant eosinophilic cytoplasm, indistinct cell borders, oval nucleus with open chromatin and indistinct nuclei

Synovial sarcoma of the heart has an overall poor prognosis. Treatment is usually excision, although the location of the tumor may make complete excision impossible. Chemotherapy and radiation therapy are often given.

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