|
Year |
2001 |
|---|---|
|
Question Number |
73. |
|
Category |
Select |
Question
A 73-year-old woman has had a painless, enlarging popliteal mass for the past 4 months. Plain radiographs show a non-minerized soft-tissue shadow. T1- and T2-weighted MRI scans are shown in Figures 17a and 17b. A biopsy specimen is shown in Figure 17c. Immunohistochemistry is positive for vimentin, smooth muscle actin, and desmin, and negative for cytokeratin and S-100. What is the most likely diagnosis?
1- Malignant fibrous histiocytoma
2- Liposarcoma
3- Synovial sarcoma
4- Fibrosarcoma
5- Leiomyosarcoma
Figures
Answer (click for answer)
Answer 5 A dreaded pathology question. There are several points to this question. The first is the appearance of the mass on MRI. The tumor is on T1 and light on T2, therefore the material is some water but very little fat. MFH, fibrosarcoma, and leiomyosarcoma have these characteristics. Synovial sarcoma frequently has calcification, would be associated with the joint and would be brighter on T2. Liposarcoma would be bright on T1 and dark on T2. The path slide shows a highly organized pattern. MFH is not highly organized; it looks like Chinese lettering or starry night pattern. Fibrosarcoma is classically a herringbone pattern, which I have to say this looks a lot like. Leimyosarcoma also is can be an organized tumor with this appearance so that is where the immuno histochemitry comes in to play
Vimentin is a marker for tissue of mesodermal origin, basically all bone and soft tissue tumors. Metastatic adenocarcinomas are negative for Vimentin, as are primary tumors of endoderm or ectoderm origin. Smooth muscle actin and desmin are markers for smooth and skeletal muscle. S-100 is a marker for tissue of cartilage, adipose, nerve sheath, chordoma, and melanoma. Cytokeratins are positive in tumors of epithelium origin (carcinomas), importantly synovial sarcoma, epithelioid sarcoma, chordoma, and adamaninoma. So the markers for smooth muscle were positive and this is a smooth muscle tumor, hence leiomyosarcoma.
Reference: Information contained in the answer is from the Basic Histology and Special Technique Review by Dr. Gary Stoprya, MD Pathology Department, Pennsylvania Hospital