Fibroma :

• They are benign tumors that can grow on fibrous or CT of any organ.
• They can be soft or hard depending on the proportion of fibres to the cell.
• Hard fibroma ( fibroma durum ) :
• a firm , dense growth growth of mature fibroblasts and collagen .
• Consists of many fibres and few cells
• Skin – dermatofibroma

Soft fibroma : ( fibroma molle )

• A soft , less dense fibrous CT mass
• It consists of many loosely connected cells and less fibroid tissue
• They can grow in all organs , arising from mesenchymal tissues
• Others forms : angiofibromas – appears as small red bumps on face

• Fibroma occur in all domestic animals , but are most common in horse
• Usually developed in adults and aged animals .
• On breed or sex prevalents
• Fibroma are most common in dermis/ subcutis , but may be present wherever there is fibrous CT .

Gross :

• Fibromas are well circumscribed neoplasm , usually firm or rubbery though some are soft
• Tumors are round / ovoid and often domesticated in skin , although some are pedunculated .
• Cut surface is usually homogenous grayish white . Some have clear , viscid, mucinous areas .
• Surface may be ulcerated and secondarily infected .

Microscopic :

• Fibroma have a characteristic structure consisting of whorls interlocking bundles of fibroblasts and collagen fibres .
• Tumor cells are usually fusiform but may be stellate in shape and have a large , pale , ovoid to elongated nuclei and multiple nucleoli .
• Mitotic figures are rare .
• Collagen fibers are dense or loose , as though separated by edema or mucinous ground substances .
• Epidermis overlying fibroma may be hyperplastic.

Fibroma must be differentiated from granulation tissue,which  generally has parallel bundles of fibroblast and collagen fibres with proliferating capillaries running at right angles.

Inflammatory polyps and focal areas of fibrosis are also confused with this tumor