Collagenous Fibroma
Khin Thway, BSc, MBBS, FRCPath
Key Facts
Terminology
Rare, benign, fibrous soft tissue neoplasm occurring mainly in adult males and consisting of paucicellular arrays of stellate and spindled fibroblasts
Clinical Issues
Usually older adults
Male preponderance
Most in subcutaneous tissue; up to 25% involve skeletal muscle; more rarely involve dermis
Most common in proximal extremity
Microscopic Pathology
Sparsely cellular patternless distributions of bland spindle or stellate cells
Hypovascular fibrous or fibromyxoid stroma
Mitotic figures rare; no necrosis
Ancillary Tests
Variable positivity for smooth muscle actin
 In this case of collagenous fibroma (desmoplastic fibroblastoma), the lesion is a well-circumscribed ovoid or fusiform mass. The hypocellularity is apparent at low power. |
 Although the tumor is largely circumscribed, focal infiltration of surrounding soft tissues may be seen  . |
TERMINOLOGY
Synonyms
Desmoplastic fibroblastoma (DF)
Definitions
Rare, benign, fibrous soft tissue neoplasm occurring mainly in adult males and consisting of paucicellular arrays of stellate and spindled fibroblasts
Reciprocal translocation t(2;11)(q31;q12) in some
ETIOLOGY/PATHOGENESIS
Developmental Anomaly
Etiology unknown
CLINICAL ISSUES
Epidemiology
Age
All ages; particularly older adults (5th-6th decades)
Gender
M > F
Site
Most occur in subcutaneous tissue
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