Fibromatosis

Clinical basics


• Non-metastasizing tumours that can be infiltrative and locally recurrent



• Commonly presents as a symptomatic painless lump in young adult to middle aged females



• Average age 35 - 45 years


• Usually hard and craggy to palpation - clinically suspicious of carcinoma



• Average size at presentation - 3.5 - 4.0 cm


• Imaging also suspicious of carcinoma



• Clinical associations:



• Trauma - possibly
• Breast implants
• Gardner's syndrome
• Familial adenomatous polyposis coli - see section on beta catenin immunostaining below


• Complications:



• Local recurrence - up to 25% of cases



• Recurrence usually occurs within three years of initial surgery
• Risk of recurrence does not correlate well with histology or even state of margins
• In spite of the above there is a trend towards more conservative management of these cases

Pathology basics


• Macro



• Average size 2.5 - 3 cm
• Stellate fibrous lesion suspicious of carcinoma



Excision biopsy of fibromatosis.


Micro


• Low power:



• Usually stellate in outline with peripheral spurs infiltrating surrounding fat and glands
• More cellular peripherally with scarring/hyalinisation centrally
• Focal lymphocytic infiltration, often peripherally, is seen in 50% of cases



• Medium power:



• Mixture of bland spindle cells and collagen
• Cellularity is not high
• Spindle cells may show a storiform or herringbone pattern
• Collagen often shows hyalinisation, at least focally - may be keloidal
• Stroma may be focally myxoid


• High power:



• Mitotic rate is low, often none are seen, more than 2-3 per 10 hpf is exceptional
• Little cellular pleomorphism
• Cytoplasmic inclusion bodies have been described



Core biopsy of fibromatosis of the breast
Click on each thumbnail to see the full sized image then click the 'Back' button to return to this page.







Immunohistochemistry:



• Nuclear staining of stromal cells with beta catenin is supportive of the diagnosis of fibromatosis - it is not specific for fibromatosis
• Staining may be patchy
• Positive beta catenin staining is uncommon in the reactive and neoplastic conditions that need to be considered in the differential diagnosis



Molecular basis:


• Beta catenin is a 92-kDa protein that binds to the cytoplasmic tail of E cadherin
• It acts in the nucleus to stimulate cell proliferation and is degraded by complexing with the adenomatous polyposis coli (APC) gene
• When mutated it is ineffectively degraded and results in uncontrolled proliferative activity
• In such situations it builds up in nuclei to the extent that it can be detected immunohistochemically
• Somatic beta catenin mutations have been detected frequently in APC-associated and sporadic fibromatoses

Excision biopsy of the same case
Click on each thumbnail to see the full sized image then click the 'Back' button to return to this page.

Return to top of page