10 June 2005 – Case of the Week #10


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This week’s case is sponsored by Invitrogen.  The Zymed® EGFr antibody clone 31G7 is the most widely referenced clone and the industry standard for EGFr detection in formalin-fixed, paraffin embedded (FFPE) tissue samples.  Zymed’s 31G7 antibody is extremely specific for EGFr and does not react with the highly homologous c-erbB-2 (HER2) protein.  Invitrogen now offers the Zymed® 31G7 antibody clone as part of a convenient, standardized immunohistochemical kit for the detection of EGFr protein expression in normal and neoplastic tissue.  Invitrogen’s Zymed® EGFr Kit is compatible with manual or automated immunostainers and offers the greatest flexibility with FFPE tissue samples.  For more information, visit www.invitrogen.com/antibodies.  Note: sponsors do NOT have access in any manner to email addresses or other personal information in the possession of PathologyOutlines.com.


We thank Dr. David Lucas, University of Michigan Hospitals, Ann Arbor, Michigan (USA), for contributing the images and some of the discussion for this case.   We invite you to contribute a Case of the Week by emailing NPernick@PathologyOutlines.com with microscopic images (any size, we will shrink if necessary) in JPG or GIF format, a short clinical history and any other images (gross, immunostains, EM, etc.) that you have and that may be helpful or interesting.  We will write the discussion (unless you want to contribute to it).  We particularly need cases of GI, GU and Gynecologic pathology.  Please only send cases with a definitive diagnosis. 


Case of the Week #10


A 30 year old man presented with a mass in the inner thigh.  MRI disclosed an enhancing, heterogeneous mass in the thigh, abutting the femur (image #1). Following open biopsy, he was treated with adriamycin-based chemotherapy, and the tumor was resected.  Grossly, it was largely gelatinous, but had areas that appeared fleshy (image #2).  Eighteen months later he developed recurrent disease in the groin, and he ultimately died of disseminated disease.


Micro images (post-chemotherapy): image #3; #4


Micro description:  The tumor showed variation from field to field.  Some of the tumor was relatively hypocellular with myxoid stroma, low grade nuclear cytology, plexiform small vascular pattern, and readily identified signet ring type lipoblasts (image #3).  However, most of the tumor was more cellular, consisting of closely-spaced, overlapping, anaplastic round cells with scant cytoplasm and readily identifiable mitotic activity.  These areas had very little stroma, and much fewer lipoblasts (image #4).


What is your diagnosis? 


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Diagnosis:  High grade myxoid / round cell liposarcoma





Myxoid and round cell liposarcomas, although histologically different, actually represent two ends of a spectrum for a tumor which almost always has the same translocation, t(12;16)(q13;p11).  They are common, and together account for 50% of all liposarcomas.  Tumors with pure myxoid features are considered to be well differentiated, and to have a good prognosis.  However, round cell features are considered high grade or poorly differentiated, and are associated with a poorer outcome, even if they represent as little as 5% of the tumor volume.  Thus, apparent myxoid liposarcomas should be sampled thoroughly to ensure that no significant round cell component is present.  This is a particular problem with needle biopsies, which may entirely miss the round cell component.


Myxoid/round cell liposarcomas frequently metastasize, based in part on the percentage of round cells, with rates varying from 23% (0-5% round cells) to 58% (>25% round cells).  They metastasize to lung and bone, as well as to other soft tissue sites. 


Histologically, pure myxoid liposarcomas resemble developing fetal adipose tissue, with a multinodular mass of low cellularity, particularly centrally.  The tumor cells are bland, spindled or round, and lie within a myxoid matrix.  Numerous lipoblasts are present, with one or many vacuoles.  There are no/rare mitotic figures.  A delicate plexiform vasculature is present, and helps differentiate this tumor from myxoma.


The round cell component is often separated from the myxoid component by a cellular transition area.  The round cells are primitive, with minimal eosinophilic cytoplasm, a high N/C ratio, and prominent nucleoli.  Lipoblasts are less frequent than in myxoid areas.  Often the cells are packed together with minimal stroma, and blood vessels are difficult to find.


As noted, almost all myxoid/round cell liposarcomas share a common t(12;16)(q13;p11) translocation resulting in the TLS-CHOP fusion gene.  Less common is t(12;22)(q13;p11) or an insertion between chromosomes 12 and 16, (12;16)(q13;p11.2p13).


References: Weiss: Enzinger and Weiss’s Soft Tissue Tumors; 2001 (4th edition), AJSP 1996;20:1047, AJSP 1996;20:171, Cancer 1996;15;77:1450




Nat Pernick, M.D.
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