A rare case of desmoplastic fibroblastoma (collagenous fibroma) of the foot

Desmoplastic fibroblastoma (DF) is a rare soft tissue tumor. It may be mistaken for other benign or even malignant tumors of soft tissue because of the small number of issues in literature. We report on an unusual presentation in the first intermetatarsal space mismatching a cyst. The mass was a circumscribed lesion, measuring 2.5 × 1.5 × 1.2 cm, and it was nodular, non-Tender, pearly-white-colored, with alternating translucent from gray-To-white areas in section. Histological evaluation showed an expansile lesion with peripheral pseudocapsule consisting of a mesenchymal hypocellular proliferation intermixed with abundant collagenous stroma. Immunohistochemical staining demonstrated a strong positive reaction for vimentin, and a weak and focal positivity for alpha-smooth muscle actin. Reaction for MUC-4, desmin, CD34, cytokeratin AE1/AE3, EMA, S100, and β-catenin were negative. After resection, at 4 years' follow-up there was no recurrence. DF may be a benign soft-Tissue tumor, however its diagnosis can be difficult due to heterogeneous symptoms and anatomical sites.