Sixty-nine cases of plantar fibromatosis and nine cases of malignant neoplasms involving the soft tissues of the sole form the basis of this study. Of the nine malignant neoplasms in this series, eight were synoviomata and one was a liposarcoma. The behavior of these tumors in the foot does not differ from that of such tumors elsewhere in the body.

In twenty-four of the sixty-nine cases of plantar fibromatosis in this series, the lesions involved plantar fascia only; in the remaining forty-five cases, both palmar and plantar fascia was involved. Peyronie's disease was found in three cases. Knuckle pads were present in three cases and keloids were associated in four. Firm subcutaneous nodules in ligamentous tissue elsewhere were noted in two cases.

The average age of onset of plantar fibromatosis was in the fourth decade of life. One third of the patients were younger than thirty years at the time of onset; the lesion was congenital in two patients. There were forty-three males and twenty-six females in this series of sixty-nine cases of plantar fibromatosis. Following surgical excision in thirty-eight cases of plantar fibromatosis in this series, the lesion is known to have recurred in twentyfive cases, in most instances within one year after operation.

The course of plantar fibromatosis is apt to be long amid only slowly progressive. In the great majority of cases the lesion is relatively asymptomatic. Pain is usually infrequent and mild.

Fibromatosis may be mistaken histologically for a malignant neoplasm on the basis of actively proliferating fibroblasts, cellular variability, mitotic figures, and, on occasions—especially after previous surgical treatment—apparently invasive properties. The histological features are diagnostic to the pathologist familiar with this lesion.

Plantar fibromatosis is a benign lesion. There is no evidence that the lesiomi ever becomes malignant.