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4 April 2013 - Case of the Week #270

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Thanks to Dr. Saroona Haroon, The Aga Khan University Hospital (Pakistan), for contributing this case. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.

May 4, 2013
The Dearborn Inn
Dearborn, MI

Michigan Society of Pathologists
2013 Spring Conference

Jeffrey Zonder, MD
Kathryn Foucar, MD
Kristin Hunt-Karner, MD



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Case of the Week #270

Clinical History:

A 65 year old man presented with multiple intestinal and mesenteric nodules. A nodule was excised and submitted in multiple pieces.

Micro images:

What is your diagnosis?


Epthelioid Gastrointestinal Stromal Tumor, Plasmacytoid variant


These immunostains were performed:

Left to right: CD34, CD117, CD38

Left to right: AE1-AE3, S100, vimentin

Gastrointestinal stromal tumors (GISTs) differentiate along lines of the interstitial cell of Cajal, the guts pacemaker cell. Behavior varies by site. In the small bowel, 30-50% of tumors have malignant behavior. The median patient age for small bowel GIST is 67 years, and patients often present with large, bulky masses that may be well circumscribed. Most (70%) tumors have the classic spindle cell pattern, but 20% are epithelioid and 10% are mixed. Epithelioid tumor cells are usually malignant appearing, with abundant eosinophilic cytoplasm.

GIST tumors are typically CD117+, CD34+ and vimentin+, as in this case. The uncommon CD117- GIST tumors may be positive for DOG1 or PKC8 (Mod Pathol 2011;24:866, Clin Med Insights Pathol 2012;5:23)

Plasmacytoid features in epithelioid GIST have been described in cytology specimens (J Cytol [serial online] 2013 [cited 2013 Apr 3];30:8, Acta Cytol 2005;49:435), and in patients with features suggestive of Carney's triad (Diagn Pathol 2011;6:52). The plasmacytoid cells which were CD38+ (a plasma cell marker), may have actually been plasma cells.

The differential diagnosis includes inflammatory fibroid polyp (spindle and stellate cells with onion skinning around blood vessels, eosinophils, lymphocytes and plasma cells; CD34+ spindle cells are KIT-, DOG1-) and lymphoid / plasma cell neoplasms (no areas resembling GIST, positive for B cell markers, CD34-, CD117-).

Tyrosine Kinase Inhibitor Therapy, including Gleevec (STI571) is usually effective treatment for GIST tumors (US National Cancer Institute-PDQ). Surgery is also an option in many cases. Historically the 5 year overall survival of small bowel GIST was only 50% (BMC Gastroenterol 2006 Oct 24;6:29), although recent reports show marked improvement (J Gastric Cancer 2012;12:243).

Nat Pernick, M.D., President
and Palak Thakore, Associate Medical Editor
PathologyOutlines.com, Inc.
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Email: NatPernick@Hotmail.com
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