Metaplastic carcinoma in an ectopic breast. (Case Histories).

We describe the case of an 81-year-old woman in whom a mass developed in the chest wall over 3 weeks. No previous mass in that area was reported. Physical examination was remarkable only for a 13 cm painless, purplish mass in the anterior chest wall. No masses were palpable in the anatomic breasts, and no lymphadenopathy was evident. Thoracoabdominal computed tomography showed a 3.5 x 7.0 cm necrotic mass; underlying muscle invasion could not be excluded. Wide excision of the tumor and underlying fascia was done, and margins were clear. Pathology showed a metaplastic carcinoma without continuity with either anatomic breast. Adjuvant radiotherapy was initiated because of the tumor's high-grade features. Twenty-six months after resection and adjuvant treatment, the patient continues to be free of disease. Metaplastic carcinoma is an unusual pathologic finding in the anatomic breast. This is the first report of its occurrence in ectopic breast tissue.

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THE MAMMARY GLAND develops primarily from the ectodermal layer during embryogenesis. In the sixth week of gestation an ectodermal thickening appears, extending from the axilla to the groin in the ventral surface of the embryo, forming the structure called the milk line. Under normal circumstances, this milk line regresses except in the thoracic region, where it forms the mammary ridge, which subsequently develops into normal breast tissue. Ectopic mammary tissue results when milk line remnants fail to regress during embryogenesis, and structures varying from rudimentary breast tissue to full-grown mammary glands develop. (1,2)

The term "ectopic breast tissue" refers to supernumerary breasts and aberrant breast tissue. Histologically, supernumerary breast tissue consists of an organized ductal system communicating with its overlying skin, whereas aberrant breast tissue is an island of unorganized secretory system, without any relationship to the overlying skin. (3) It has been postulated that a genetic factor is the cause. (4,5)

The incidence of ectopic breast tissue occurrence ranges from 0.6% to 6.0%. It varies with different ethnic populations, occurring more frequently among Japanese people and less frequently among whites. (3) Although the occurrence of ectopic breast tissue is low, it is reported to be more prone to malignant transformation than the normal anatomic breast. (6) In this regard, it is hypothesized that stagnation arising in the ductal lumens of the aberrant breast tissue is a promoting factor for the development of malignancy. (7)

Ectopic breast tissue is subject to the same pathologic processes affecting the normal anatomic breasts and frequently responds to hormonal stimulation associated with menses, lactation, or pregnancy; engorgement and discomfort may occur. (8) Cases of pathologic conditions occurring in ectopic breast tissue include phyllodes tumors, (2) cystic disease, (9) fibroadenoma, (10) ductal and lobular carcinomas, (11) Paget's disease, (12) and leiomyosarcoma, (13) among others. Also of interest is the finding that papillary hydradenoma of the vulva is not a sweat gland neoplasm as traditionally believed but an intraductal papilloma arising from ectopic breast parenchyma. (14)

There have been multiple reports of malignant transformation of ectopic breast tissue in various locations, including axillary, parasternal, subclavicular, scapular, vulvar, and chest wall. The majority of reports agree that the most common location is the axilla, comprising 55% to 65% of the cases reported. The most unusual locations reported are the scapula and chest wall. (3) In the cases of malignant transformation of ectopic mammary tissue, the most frequently occurring manifestation is infiltrating ductal carcinoma, (3,10) comprising 79% of all malignancies. Medullary and lobular carcinoma are both seen in 9.5% of the cases. (10) Besides these, there have been isolated reports of Paget's disease, (12) cystosarcoma phyllode, (15) and papillary carcinoma. (16)

The unique occurrence of metaplastic carcinoma in one of our patients prompted this article. Our case is one of the most unusual pathologic presentations of breast cancer. In this case, the malignancy developed in an ectopic breast located on the anterior chest wall, an uncommon location for an ectopic breast cancer. As of this writing, ours is the only report of metaplastic carcinoma occurring in an ectopic breast. The clinical features, treatment, and outcome are described, and the literature on metaplastic and ectopic breast cancer is reviewed.

CASE REPORT

Our patient was an 81-year-old white woman with no significant medical history who came to our clinic in March 1998. She complained of a mass on the right anterior chest wall. The patient said that the mass developed about 2 weeks before her hospital visit. She described it as painless. She denied any previous neoplasia or family history of breast cancer. The patient also denied awareness of any mass or nipple-like structure in the area where the tumor developed. She reported no weight loss, fever, or previous trauma to the area of the chest involved.

At physical examination, the patient was a healthy, elderly woman in no acute distress, with a 13 x 14 cm purplish mass in/on the anterior chest wall. It was fluctuant, nontender to palpation, and located 5 cm under the right mammary crease. No axillary, supraclavicular, or inguinal adenopathy was identified, and the remainder of the physical examination was unremarkable. Ultrasonography of the chest wall mass showed a complex cystic mass with a solid central component, as well as a single feeding vessel arising from the chest wall. This study was reported as being suggestive of a benign or malignant tumor.

The mass was drained, yielding several hundred milliliters of bloody serous fluid but leaving a residual mass, which was biopsied. The biopsy showed metaplastic carcinoma of the breast. An extensive workup, including breast, nasopharyngeal, gynecologic, thoracic, and abdominopelvic studies, was done to seek any occult malignancy as a source for the lesion on the chest wall.

Mammograms of both breasts showed benign findings. Results of laryngoscopy, chest radiography, abdominopelvic ultrasonography, Pap smears, and gynecologic examination all were unremarkable. Computed tomography of the thorax, abdomen, and pelvis yielded negative results, except for a 3.5 x 7.0 cm inflammatory, necrotic mass of the anterior chest wall. Invasion of the anterior aspect of the right chest wall could not be excluded.

Wide excision including the underlying muscle fascia was accomplished. The tumor measured 7 x 4 cm. The specimen showed a malignant epithelial neoplasm with focal areas of small duct-like structures lined by epithelium, invading the dermis, but with no lymphatic or vascular invasion. The final interpretation was done by the Louisiana State University department of pathology and was reported as a unique case of metaplastic carcinoma of the breast. The tumor margins were said to be free of malignancy. To assess the likelihood of response to adjuvant hormonal therapy, the specimen was studied for the presence of estrogen and progesterone receptors; results were reported as negative. Since the size of the actual tumor was larger than 5 cm but no extension into the chest wall was found, the tumor was considered to be T3 N0 M0 (stage IIB).

The case was discussed by our tumor board. Taking into consideration the undifferentiated characteristics of the tumor and its high-grade features, it was recommended to proceed with adjuvant radiotherapy. The patient completed 7 weeks of external beam radiotherapy, receiving a total of 5,400 rads. The patient received follow-up in the surgery breast clinic. In April 2000, 2 years after surgery, she showed no signs suggestive of recurrence. Mammography continued to show no signs of malignancy.

DISCUSSION

Metaplastic carcinoma is a generic term used to identify breast carcinoma of a ductal type, in which the predominant component of the neoplasm has an appearance other than distinct epithelial and glandular characteristics; extensive metaplastic changes, including squamous cell, spindle cell, and heterogeneous mesenchymal growth patterns, are seen. The variation in appearance of these neoplasms has led to a variety of designations, including metaplastic carcinoma, spindle cell carcinoma, carcinosarcoma, and carcinoma with osseous metaplasia, among others. According to Oberman,(17) in a clinicopathologic study of metaplastic carcinoma done at the University of Michigan, Ann Arbor, there is a lack of correlation between the different growth patterns and the disease prognosis, supporting the idea that all the metaplastic variants represent microscopic manifestations of a single entity.

This unusual breast neoplasm is found in 0.02% of all the cases of cancer in the anatomic breast.(18) This neoplasia is peculiar for its undifferentiated nature, appearing locally circumscribed in most instances and with a paucity of lymph nodal involvement, which belies its aggressive clinical behavior.(17) The incidence of lymph nodal spread ranges from 0% to 25%, according to previous clinicopathologic reviews.(17,19) The propensity for pulmonary metastatic spread of these tumors, in the absence of lymph node involvement, suggests that the clinical staging systems as prognostic indicators for this breast carcinoma have a limited usefulness. Oberman(17) reported the largest study, compiling 29 cases of metaplastic carcinoma of the anatomic breast. He found that the only parameter that reliably correlated with the prognosis was the size of the tumor, which if less than 4 cm was said to be a good indicator for a favorable outcome.

In 1994, Marshall et al(3) reviewed the literature, summarizing all cases of cancer of ectopic breast from 1865 through 1994, including all the ectopic locations and histologic diagnoses. He found only three cases of ectopic breast cancer arising in the chest wall, the last one having occurred in 1958. Since 1991, only two additional cases have been reported, one by Marshall et al(3) in 1994 and another by Vargas et al(20) in 1995. According to our literature review, there has never been a case reported of metaplastic carcinoma or any of its variants originating in mammary tissue in any of the ectopic breast tissue locations.

As described earlier, the clinical manifestation of this unique ectopic breast tissue neoplasm was as a rapidly growing cystic mass with purplish discoloration, located on the right anterior aspect of the chest wall. After ruling out any occult primary process, this mass was initially diagnosed by CT as a primary soft tissue sarcoma, showing a partially necrotic mass with contrast enhancement (Fig 1). The macroscopic tumor inside the specimen consisted of a solitary mass measuring 5.7 x 3.8 x 4.0 cm with margins and some liquefaction necrosis. Microscopically, the hematoxylineosin stain showed an epithelial malignant neoplasm with polygonal to spindle cells embedded and mixed with focal areas of dense fibrosis. Areas of small duct-like structures lined by epithelium taking an almost squamous appearance were found in parts of the tissue. The tumor did not invade the lymphatic or blood vessels, and all the margins were free of malignancy without any continuity between the primary tumor and the anatomic breast ( Fig 2).

The specimen was negative for estrogen and progesterone receptors. These findings are consistent with the undifferentiated nature of this histologic type and the absence of hormone receptor markers reported in previous cases of metaplastic carcinoma. Oberman,(17) in his clinicopathologic review of metaplastic carcinoma, found no cases positive for hormone receptors. Similar results were reported by Gersell and Katzenstein(21) and Rostock et al.(22)

It is impossible to make any conclusion about the appropriate treatment of a metaplastic carcinoma arising in ectopic mammary tissue, since this is the first case reported. Previous reviews of series of ectopic breast cancer show no additional advantage of breast resection in the absence of a primary tumor in the breast itself. The prognosis of ectopic breast carcinoma is obviously difficult to establish, since follow-up is limited or absent in the cases reported, and there is no uniform therapeutic approach for this neoplasia. It seems that this type of malignancy has a more dismal outlook than one arising in the pectoral breast, probably related to a lack of suspicion on the part of the surgeon, leading to a delayed diagnosis. Early lymph node involvement is likely, since most of the ectopic breast neoplasms arise in the axillary area, adjacent to the axillary node basin.

According to the review of 64 cases of ectopic breast cancer in the axilla reported by Evans and Guyton,(23) radical or modified radical mastectomy offered no advantage in outcome over wide local excision of the axillary breast combined with regional node dissection. In general, it is the consensus that prophylactic ipsilateral mastectomy has no role in the management of a single ectopic breast cancer.(3)

In the case of a metaplastic carcinoma of the anatomic breast, Huvos et al(24) reported different rates of nodal involvement according to the histologic characteristics of the primary tumor; however, no study has shown any significant correlation between these findings and the clinical outcome. When compared with the most frequently occurring breast malignancy, infiltrating ductal carcinoma, axillary node metastasis from metaplastic carcinoma of the breast is present significantly less often (47% vs 23%) (19) In addition, no clinicopathologic information other than size has correlated accurately with the outcome. These observations are limited by the small number of cases, variable follow-up, and different treatment modalities.(17)

CONCLUSION

The purposes of our report are to collect and combine up-to-date information pertinent to ectopic breast cancer and metaplastic breast carcinoma and to suggest a reasonable approach when faced with an unusual situation such as in our case. The presence of an irregular mass in the anterior chest wall, with a CT scan highly suggestive of malignancy, mandates a core biopsy, which if positive for metaplastic carcinoma requires complete excision. In metaplastic carcinoma, the rate of nodal involvement is imprecise and in general its occurrence seems to be more unusual than in invasive ductal carcinoma; therefore, the lesion location and its proximity to the nodal basin would dictate whether nodal dissection should be done. Cady(25) analyzed the impact of axillary node dissection in anatomic breast carcinomas with low rates of axillary metastasis. In a hypothetical group of breast cancer patients with a 15% chance of lymphatic spread, an axillary dissection in addition to the resection of the primary tumor yielded a minor gain in disease-free survival when compared with the same type of patients in whom axillary dissection was not done. According to Cady's review, only one of 100 patients would benefit in the long term with this approach.

Fisher et al(26) reported results of a multicentric randomized clinical trial in 1985 comparing disease-free survival in anatomic breast cancer with clinically negative nodes using (1) modified radical mastectomy; (2) simple, total mastectomy plus local and axillary radiation; and (3) simple mastectomy without radiation or axillary dissection. (However, axillary dissection was subsequently performed in the last group if involvement of axillary nodes was detected during follow-up.) The study showed no disease-free survival difference among the groups, supporting the questionable longterm benefit of axillary dissection in addition to the mastectomy in situations with a low risk of lymph node metastasis.

Metaplastic carcinoma has a low potential for lymph node metastasis. Following the rationale set forth in the studies by Cady(25) and Fisher et al,(26) we believe that wide local excision with cancer-free margins for local control would be appropriate for this situation, given the low risk of lymphatic spread and the absence of an obvious lymphatic drainage basin. Furthermore, since this neoplasia has poorly differentiated histologic characteristics, the patient would be a candidate for adjuvant radiation therapy as suggested by Rosen and Ernsberger.(27)

Even though the studies of Cady(25) and Fisher et al(26) involved malignant neoplasias in the anatomic breast (no metaplastic types), from them we can support the rationale of avoiding routine nodal dissection in cases in which the risk of lymphatic metastasis is low, as in our patient's case.

In summary, this is an unusual case of a patient with ectopic metaplastic breast cancer. The lymph nodes were clinically negative for malignancy, and wide local excision resulted in tumor margins free of malignancy; the patient also received postoperative radiotherapy. After 26 months the patient remained free of recurrent disease. We think ours was a reasonable approach for such an unusual disease and case.

References

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(4.) Iwai T: A statistical study on the polymastia of the Japanese. Lancet 1907; 2:753-759

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(6.) Nakao A, Saito S, Fumiyuki I, et al: Ectopic breast cancer: a case report and review of the Japanese literature. Anticancer Res 1998; 18:3737-3740

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(10.) Greer KE: Accessory axillary breast tissue. Arch Dermatol 1974; 109:88-89

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(12.) Martin VG, Pellettiere EV, Gress D, et al: Paget's disease in an adolescent arising in a supernumerary nipple. J Cutan Pathol 1994; 21:283-286

(13.) Alessi E, Sala F: Leiomyosarcoma in ectopic areola. Am J Dermathopathol 1992; 14:165-169

(14.) Rosai J: Ackerman's Surgical Pathology. St. Louis, CV Mosby Co, 8th Ed, 1996, pp 1615-1616

(15.) Saleh HA, Klein LH: Cystosarcoma phylloides arising synchronously in right breast and bilateral axillary ectopic breast tissue. Arch Pathol Lab Med 1990; 114:624-626

(16.) Walker A, Fectiner RE: Papillary carcinoma arising from ectopic breast in an axillary lymph node. Diagn Gynecol Obstet 1982; 4:141-145

(17.) Oberman HA: Metaplastic carcinoma of the breast: a clinicopathologic study of 29 patients. Am J Surg Pathol 1987; 11:918-929

(18.) Smith DM, Rongaus VA, Wehmann TW, et al: Metaplastic breast carcinoma.J Am Ostheopath Assoc 1996; 96:419-421

(19.) Chhieng C, Cranor M, Lesser ME, et al: Metaplastic carcinoma of the breast with osteocartilaginous heterologous elements. Am J Surg Pathol 1998; 22:188-194

(20.) Vargas J, Nevado M, Rodriguez-Peralto JL, et al: Fine needle aspiration diagnosis of carcinoma arising in an ectopic breast. Acta Cytol 1995; 39:941-944

(21.) Gersell DJ, Katzenstein AA: Spindle cell carcinoma of the breast. Hum Pathol 1981; 12:550-560

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RELATED ARTICLE: KEY POINTS

* An 81-year-old woman had a mass in the anterior chest wall with radiographic suspicion for sarcoma.

* Pathologic examination was reported as metaplastic carcinoma of an ectopic breast.

* Treatment with wide local excision and adjuvant radiotherapy resulted in a 2-year disease-free survival.

From the Department of Surgery, Louisiana State University Medical Center, New Orleans.

Reprint requests to Manuel Caceres, MD, 5855 Walnut Creek Rd, Apartment A205, River Ridge, LA 70123.