A new case of a rare variant of papillary carcinoma of the thyroid gland with fibromatosis-like stroma is reported. The patient was a 43-yr-old woman who had a well demarcated tumor that showed an expansive growth from the left thyroid lobe into perithyroidal soft tissues. Histologically, the tumor was composed predominantly of a fibromatosis-like stroma in which were diffusely dispersed small follicles of papillary carcinoma. At the advancing front of extrathyroidal extension of the tumor, fibromyxomatous changes of soft tissues were preceded by infiltration of the papillary carcinoma component. Immunohistochemistry and electron microscopy showed that the stromal cells had a myofibroblastic nature. One metastatically involved lymph node did not show fibromatosis-like stroma. The patient has remained well with no evidence of recurrence for 1 yr.