A Zebra in Sheep’s Clothing: A Case of PUS Masquerading...
A Zebra in Sheep’s Clothing: A Case of PUS Masquerading As Echinococcus
Learning Objectives
• Pleomorphic Undifferentiated Sarcoma (PUS) is a rare cancer typically found in the soft tissues of the extremities or trunk.
• PUS of the spleen is very rare, with only one case occurring in someone under the age of 40 in the literature.
Case
C Nguyen BS, J Chen MD, T Dempsey MD MPH, E Tong MD MA
University of California, Davis Medical Center, Sacramento CA
Clinical Course
Repeat CT confirmed presence of enlarging cystic lesions in the spleen. Due to profound anemia and concern for intraparenchymal hemorrhage, surgery was consulted and splenectomy recommended. Post-splenectomy, she had rapid clinical improvement. Preliminary pathology revealed sarcoma without infection. After discharge, analysis of the tumor by two independent pathologists failed to show evidence of differentiation and patient was diagnosed with PUS. An outpatient PET scan showed LUQ hypermetabolic activity and patient was started on chemotherapy.
HISTORY OF PRESENT ILLNESS
A 35 year old Caucasian woman with travel to the Middle
East 6 months ago presents with fever and diffuse myalgias.
Patient initially had cough after returning from abroad.
CXR obtained following failed antibiotic therapy showed
LUQ calcified structure, prompting further imaging. CT and
MRI revealed several splenic lesions concerning for
Echinoccocus. Despite negative Echinococcal titers, patient was treated empirically with albendazole per ID without improvement.
PHYSICAL EXAM
Patient had a temperature of 38.2C and a heart rate of 130.
Patient appeared pale and anxious. Abdominal exam remarkable for LUQ tenderness and hepatosplenomegaly.
The rest of the exam was unremarkable.
LABORATORY DATA
• WBC 17 and Hgb 6.6
• BMP and AST/ALT were normal
• Alk phos was 350 (normal <150)
• Lactic acid 1.2
Figure 1:
Coronal and sagittal views of CT Abdomen demonstrating large calcified splenic cyst (9.2cm) surrounded by smaller cysts.
Figure 2:
Gross surgical specimen showing solid tumors within spleen.
Figure 3
: Classic storiform pattern of PUS.
Teaching Points
• Formerly known as malignant fibrous histiocytoma, PUS most commonly affects people in the 6 th and 7 th decade of life. High grade pleomorphic sarcomas have an overall 5-year survival rate of 50 – 60% and age, subtype and staging of the sarcoma are among the most important prognostic factors.
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• Macroscopically, these tumors are heterogeneous, well-circumscribed masses with most measuring 5 – 15cm in diameter.
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• The diagnosis is one of exclusion. These undifferentiated tumors do not express antigens suggestive of other types of sarcomas on immunohistochemistry.
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• Treatment consists of surgery +/- chemotherapy or radiation, but the best treatment has yet to be elucidated
References
1. Weiss SW (1982). Malignant fibrous histiocytoma. A reaffirmation. Am J Surg Pathol 6: 773-784.
2. Gustafson P (1994). Soft tissue sarcoma.Epidemiology and prognosis in 508 patients. Acta Orthop Scand Suppl 259:1-31.
3. Matushansky, Igor, et al. "MFH classification: differentiating undifferentiated pleomorphic sarcoma in the 21st Century." Expert review of anticancer therapy 9.8 (2009): 1135-1144.
4. Fletcher CDM, van den Berg E, Molenaar WM: Pleomorphic malignant fibrous histiocytoma/undifferentiated high grade pleomorphic sarcoma. In World
Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone. Edited by Fletcher CDM, Unni KK,
Mertens F. Lyon: IARC Press; 2002:294-296.
* Special thanks to Dr. Mingyi Chen and Dr. Christina DiLoreto for pathology and CT images, respectively.
