Course Map: Soft Tissue Tumors: Leiomyosarcoma and Leiomyoma

Leiomyosarcoma and Leiomyoma
This is the common sarcoma of adults and does not differ from those occurring elsewhere [10]. The differential diagnosis of leiomyosarcoma includes spindle cell (sarcomatoid) carcinoma and myofibroblastic proliferations, since these three constitute the great majority of spindle cell bladder lesions. Wide sampling may be needed to find in-situ or differentiated foci of carcinoma in the spindle cell carcinoma. Myofibroblastic lesions are discussed in the section dealing with tumor-like lesions.
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	Figure 1: Leiomyoma. Smoothly rounded contours such as we see here, are not usually present in leiomyosarcomas.
	Figure 2: Same case as Figure 1. Notice that the character of the cells in the leiomyoma is not significantly different from that of the normal muscularis propria on the right side of this field.
	Figure 3: Leiomyosarcomas of the bladder often present as polypoid masses projecting into the bladder lumen. However, this may be seen also with other spindle cell lesions such as spindle cell carcinoma and myofibroblastic tumors.
	Figure 4: Unlike most sarcomas, leiomyosarcomas usually show long, sweeping, discrete fascicles (arrows) of spindle cells (except for the very high grade tumors).
	Figure 5: Leiomyosarcoma. The fascicular morphology is more subtle in this case than that in Figure 4, but nuclear pleomorphism requires a diagnosis of sarcoma.
	Figure 6: This is a transurethral resection of a bladder tumor. On the left, it would be a problem distinguishing between leiomyoma and leiomyosarcoma . On the right, it is clearly anaplastic. We show this photograph in order to stress that a sampling of a part of a smooth muscle tumor may show a misleading histiology.