Fibromatosis: the breast cancer imitator.

Abstract: Fibromatosis of the breast is a rare benign tumor that should be included in the differential diagnosis for breast cancer. It is usually indistinguishable from malignancy on ultrasound, mammography, physical examination, and on gross evaluation. Distinction is easily made by histologic findings. This benign tumor does not metastasize, but is locally aggressive and tends to recur postoperatively, which accounts for considerable morbidity. We present two cases and a discussion from the perspective of the radiologist, the surgeon, and the pathologist.

Key Words: breast tumor, extra-abdominal desmoid, fibromatosis

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Fibromatosis of the breast, sometimes labeled as extra-abdominal desmoid, is a rare benign tumor that creates a dilemma for the clinician, radiologist, and surgeon. Approximately 100 cases have been reported in the literature, 33 from the Armed Forces Institute of Pathology. (1,2) It is indistinguishable from malignancy on physical examination and breast imaging. It does not metastasize, but has a high incidence of recurrence, as high as 27%, after resection. (3) Thus, wide excisions with clear margins are required surgically. We present two cases of fibromatosis of the breast, one extending to the pectoralis muscle and the other contained within the breast parenchyma.

Case Reports

Patient 1

A 50-year-old obese female with no significant prior medical, surgical, or family history presented with a 1 month history of a palpable lump in the upper inner quadrant of the left breast. She denied associated symptoms. On clinical examination a 1.5 X 1.5 cm solitary mass was noted in the 11:00 position of the left breast. The mass was tender, firm, solid, and mobile. Tethering of the skin was present. Mammography showed a spiculated mass and no associated microcalcifications or architectural distortion (Fig. 1). Ultrasound examination revealed that the mass was solid, hypoechoic, and had lobulated margins (Fig. 2). Breast imaging was classified as BI-RADS-4, suspicious for malignancy, and patient was referred for surgical evaluation. Excisional biopsy was performed, and the histologic findings interpreted as fibromatosis. No further surgery has been performed and at 6 years after the excisional biopsy she is without recurrence.

Patient 2

A 31-year-old healthy female presented for evaluation of a left breast mass noted 2 months earlier on self-examination. Family history was positive for breast cancer in the maternal grandmother. There was no significant past medical or surgical history and the patient was not taking any medications.

On physical examination, obvious skin tethering was present in the superior medial quadrant of the left breast, remote from the nipple and adjacent to the sternum. A 3 cm hard mass was located directly under this tethering. This mass was mobile from the skin but appeared to be adherent to the underlying pectoralis muscle. There was no nipple discharge or adenopathy. Mammography revealed an ovoid hyperdense mass with associated elevation of the immediate deep pectoralis muscle suspicious of invasion (Fig. 3). The borders of the mass were spiculated and there were no microcalcifications. Ultrasound examination demonstrated a solid mass with thick internal septations and irregular lobulated margins (Fig. 4). The examination was categorized as BI-RADS-4, suspicious for malignancy, and the patient was referred for surgical evaluation.

At the time of surgery, the mass was excised with an attempt to obtain grossly negative margins (Fig. 5). The mass appeared to invade the pectoralis muscle; therefore, muscle was included in the margins of the tissue excised (Fig. 6). As of this writing, less than one year has passed since the patient underwent surgery.

Discussion

Fibromatosis usually occurs in the abdominal wall and superficial muscular-aponeurotic tissues of the extremities. Pathologic diagnosis of the breast is extremely rare, with an incidence as low as 0.2% of breast tumors, and may arise from the pectoralis muscle/fascia or mammary tissue primary. (4)

The etiology of mammary fibromatosis is unknown. A few reported cases suggest that trauma, sex steroid hormones, and Gardner syndrome may play a role. The majority of cases are spontaneous with no history of trauma or Gardner syndrome, and are hormone receptor negative. (2,5)

The tumor has only been reported in women, and has occurred at any time after onset of puberty, with an average reported age of 30 to 40 years. (2) The most common presenting complaint is skin tethering. This is caused by fibrous tissue contraction versus desmoplastic reaction, which is attributable to tethering associated with malignancy. (6) The mass is usually painless, palpable, and mobile.

[FIGURE 1 OMITTED]

On breast imaging, the tumor has malignant features. Mammographic findings include a spiculated mass without microcalcifications, and no associated adenopathy. On ultrasound evaluation, the finding is usually an irregular mixed hypoechoic mass similar to that seen with malignancy. (6)

Grossly, appearance varies and size ranges significantly, with a mean diameter of 2.5 cm. Most lesions are lobulated, firm, poorly defined, and grayish in color. Spiculations and pectoralis muscle/fascial involvement may not be apparent intraoperatively because the lesion may appear to be pushing on existing breast lobules without destroying or infiltrating tissue. (3,6)

The tumor can best be distinguished from other entities histologically; cytologic examination by fine needle aspiration is usually not diagnostic. (5) The lesion consists of fairly monotonous, bland spindle cells with variable amounts of intervening collagen. Radial scars have a similar gross appearance, but histologically, the connective tissue component of radial scars has more collagen and is hypocellular. The cellularity-to-collagen ratio decreases with age, suggesting involution. Multiple cases of spontaneous regression have been reported. The lesions lack malignancy features such as high mitotic rate, cellular atypia, necrosis, and vascular invasion. Lymphocytic infiltrates are sometimes present at the periphery of the lesion, in contrast to inflammatory lesions which generally demonstrate inflammatory cells throughout the lesional tissue. (2) Entrapped lobular tissue may occasionally lead to a histologic misdiagnosis of carcinoma, but the histologic findings are otherwise quite distinctive. (7)

[FIGURE 2 OMITTED]

The surgical management of these lesions is wide local excision because of the locally invasive nature and potential for recurrence of the neoplasm. When surgical margins are positive following the initial excision, those neoplasms arising from the pectoralis are reported to have an incidence of local recurrence of 57%, while those primary to breast are reported to have a 21% risk of recurrence. (3)

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

Following the initial excision, the risks of recurrence are discussed with the patient. Factors reported to increase the risk of recurrence include age (younger patients have an increased risk), multifocality, involved margins, and site of origin (breast or pectoralis). If re-excision would result in significant cosmetic or functional deformity, the option of close observation is preferred.

Local recurrences usually occur within 3 years of the initial diagnosis. During this period of time, close follow-up is mandatory. With recurrence, the extent and anatomic involvement is evaluated. Although radical surgery is the "best" way to eradicate the disease, the long-term morbidity must be considered in light of the fact that the tumor does not metastasize and may spontaneously regress. Radical surgery for resection should be performed unless the results are mutilation or loss of function.

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

The use of radiation has been proposed both as a means to prevent local recurrence as well as to treat local disease. There is not enough evidence in the literature to substantiate or discredit the use of radiotherapy in this disease. (8,9)

Conclusion

Fibromatosis is a rare, locally aggressive, and benign breast tumor that has no predilection for age, family history, or exposure factors. It mimics breast cancer on physical examination, mammogram, breast ultrasound, and gross specimen. The tumor is best differentiated histologically. Complete surgical excision is the proven method of treatment, and patients should be followed closely for at least 3 years to monitor for recurrence.

We all agree that your theory is crazy, but is it crazy enough?
--Niels Bohr

Accepted January 8, 2004.

References

1. Nakano S, Ohtsuka M, Hasegawa T, et al. Fibromatosis of the breast: a case report. Breast Cancer 2002;9:179-183.

2. Devouassoux-Shisheboran M, Schammel MD, Man YG, et al. Fibromatosis of the breast: age-correlated morphofunctional features of 33 cases. Arch Pathol Lab Med 2000;124:276-280.

3. Rosen PP, Ernsberger D. Mammary fibromatosis. A benign spindle-cell tumor with significant risk for local recurrence. Cancer 1989;63:1363-1369.

4. Yiangou C, Fadi H, Sinnett HD, et al. Fibromatosis of the breast or carcinoma? J R Society of Medicine 1996;89:638-640.

5. Kalbhen CL, Cooper RA, Candel AG. Mammographic and stereotactic core biopsy findings in fibromatosis of the breast: case report. Can Assoc Radiol J 1998;49:229-231.

6. Leibman AJ, Kossoff MB. Sonographic features of fibromatosis of the breast. J Ultrasound Med 1991;10:43-45.

7. Lopez-Ferrer P, Jimenez-Hefferman JA, Vicandi B, et al. Fine-needle aspiration cytology of mammary fibromatosis: report of two cases. Diagn Cytopathol 1996;17:363-368.

8. Godwin G, McCulloch TA, Sully L. Extra-abdominal desmoid tumour of the breast. Br J of Plast Surg 2001;54:268-271.

9. Ng WH, Lee JS, Poh WT, et al. Desmoid tumor (fibromatosis) of the breast. A clinician's dilemma-a case report and review. Arch Surg 1997;132:444-446.

RELATED ARTICLE: Key Points

* Fibromatosis of the breast is indistinguishable from malignancy on clinical and radiologic examination, and can be identified only after surgical excision and histologic evaluation.

* The etiology of fibromatosis is currently unknown.

* Fibromatosis is locally aggressive and has a high risk of recurrence.

Tamera Hughes Matherne, MD, Allan Green Jr, MD, J. Allan Tucker, MD, Donna Lynn Dyess, MD

From the Departments of Radiology, Pathology, and Surgery, the University of South Alabama, Mobile, AL.

Reprint requests to Tamera Hughes Matherne, MD, 9425 Yorktowne Way, Mobile, AL 36695. Email: [e-mail]