Rare, but considered the most common benign mesenchymal tumor in the bladder.
More common in female, may present with obstructive symptoms.
Gross: well-circumscribed submucosal mass (< 2 cm) with firm gray-white trabeculated cut surface; rare cases of up to 25 cm in size (image A).
Fascicles of spindle cells with cigar-shaped nuclei(image B).
No mitoses or necrosis.
Image C (click on the image above)
Image D (click on the image above)
Rare, but is the most common type of sarcoma that arises in the bladder.
More common in male.
Gross: lobulated gray-tan mass (mean 7 cm) often with necrosis, with or without ulceration of the overlying mucosa.
Fascicles of spindle cells with cigar-shaped nuclei that is more atypical (image C) & (image D).
Abundant mitoses and necrosis.
DDX: sarcomatoid carcinoma and myofibroblastic tumor, which both similar to LMS express smooth muscle actin (traditionally a smooth muscle tumor marker) and pankeratin (traditionally an epithelial marker) (beware of these overlap).