11 June 2009 – Case of the Week #149
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Thanks to Drs. Asmaa Gaber Abdou and Nancy Youssef Asaad, Menoufiya University, Egypt, for contributing this case. To contribute a Case of the Week, email [email protected] with the clinical history, your diagnosis and diagnostic microscopic images in JPG, GIF or TIFF format (send as attachments, we will shrink if necessary). Please include any other images (gross, immunostains, etc.) that may be helpful or interesting. We will write the discussion (unless you want to), list you as the contributor, and send you $35 (US dollars) by check or PayPal for your time after we send out the case. Please only send cases with high quality images and a diagnosis that is somewhat unusual (or a case with unusual features).
Case of the Week #149
A 50-year-old woman presented with a thigh mass, which was excised.
What is your diagnosis?
The mass showed cords of cells floating in myxoid or mucoid material, admixed with occasional physaliferous (multivacuolated) cells. The original diagnosis was liposarcoma, but after review, immunostains were performed showing tumor cells that were immunoreactive for cytokeratin, EMA, S100, and vimentin, which confirmed the revised diagnosis of parachordoma.
Parachordoma is a rare peripheral tumor which usually affects deep soft tissues adjacent to bones and tendons. It is characterized by myxoid or hyaline material containing large, rounded eosinophilic cells. The tumor almost always contains a small number of physaliferous cells (Am J Surg Pathol 1999;23:1059). It stains positively for S100, vimentin, CK8/18, and EMA, and negative for CK1/10. Type 4 collagen is also present around nests of cells.
The differential diagnosis includes:
• Liposarcoma. These tumors have variable lipoblasts, which are also multivacuolated, but have atypical nuclei. They also have a prominent component indicated by the subtype (well differentiated, dedifferentiated, myxoid/round cell, pleomorphic or sclerosing), and are keratin negative.
• Extraskeletal myxoid chondrosarcoma. These tumors have a neoplastic cartilaginous component with long chains of cells, are keratin negative, and have a characteristic t(9;22).
• Chordoma (primary or metastatic). Primary chordomas occur on the craniospinal axis, and have prominent physaliferous cells. Some authors consider the immunostaining pattern to be similar to parachordoma (Pathol Int 2004;54:364), but some believe that CK1/10 staining is helpful to differentiate these entities. Metastatic chordoma must be ruled out clinically.
Parachordomas typically have benign behavior. Wide resection is usually adequate treatment, and recurrences are rare (Adv Anat Pathol 2000;7:141). However, to date, five cases of metastatic tumor have been reported (J Cutan Pathol 2009;36:270).
Additional references: Stanford University
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