Rhabdomyosarcoma

We report the case of a primary breast rhabdomyosarcoma in a 51-year-old white woman. The tumor occupied the upper outer quadrant of the right breast. There was no association with the underlying pectoral muscle, and the patient was free of any other benign or malignant neoplastic processes outside the breast. Microscopically, the breast tumor was composed of primitive myoblasts and numerous rhabdomyoblasts at various stages of development, many of which exhibited cytoplasmic cross striations on routine hematoxylin-eosin staining.

(Arch Pathol Lab Med. 1998;122:747-749)

Pure nonepithelial primary malignant neoplasms of the female breast are rare, comprising fewer than 1% of all breast malignancies. They represent a heterogenous group of mesenchymal neoplasms, histopathologically similar to their counter parts arising from mesenchymal tissues elsewhere in the body.

In this report, we present an extremely rare case of a primary breast rhabdomyosarcoma in a 51-year-old white woman. To the best of our knowledge, this is the third documented case of a primary breast rhabdomyosarcoma reported in the literature.

REPORT OF A CASE

A 51-year-old white woman was hospitalized for evaluation of a right breast mass that grew rapidly in a 3-month period. On physical examination, a right breast mass occupying the upper outer quadrant was identified. The overlying skin was movable; there was no nipple discharge, nipple retraction, skin discoloration or ulceration, and no fixation to the underlying tissues. Axillary lymph nodes were not palpable. A thorough clinical and radiographic examination failed to reveal any other neoplastic process outside the affected breast. The breast lesion was surgically removed along with an ample portion of the surrounding fat tissue. Recovery was uncomplicated, and the patient was discharged a week later. Six months postoperatively, the patient was free of metastatic disease. The patient was lost to follow-up after that time.

PATHOLOGIC FINDINGS

Grossly, the surgical specimen consisted of a piece of breast tissue measuring 7 x 7 x 6 an. On sectioning, a solid nonencapsulated tumor mass with ill-defined borders was found to occupy the central part of the surgical specimen. It measured 4.5 cm in diameter, had a homogeneous cut surface with focal areas of necrosis, was of a soft consistency, and was light gray. Multiple sections from the tumor and the surgical margins were submitted for histologic evaluation.

Microscopically, the tumor consisted predominantly of round or moderately elongated cells resembling rhabdomyoblasts at various stages of differentiation. These cells were characterized by densely eosinophilic cytoplasm with prominent peripheral multivacuolation. Cytoplasmic fibrillation suggestive of cross striations, as seen in many rhabdoid tumors, was evident in many of these cells. Their nuclei were round and densely stained, occupying the central or a more peripheral region of the cell (Fig 1). Scattered among these cells were many round or moderately elongated rhabdomyoblasts with prominent cytoplasmic cross striations, which were easily identified on routine hematoxylin-eosinstained sections (Fig 2). The neoplastic cells grew in clusters or exhibited a more diffuse growth pattern in a loose and rather edematous stroma, which extended into a narrow zone of the surrounding breast tissue. Sampling of all surgical margins (ie, median, lateral, anterior, and posterior) failed to reveal presence of tumor.

COMMENT

Primary nonepithelial malignant tumors of the female breast represent a diverse and heterogenous group of mesenchymal neoplasms. The Table summarizes the diverse histopathologic types that have been reported in the literature. The incidence of mesenchymal neoplasms of the breast is extremely low, comprising less than 1% of all breast malignancies. Oberman1 reported 13 cases from the files of the University of Michigan between 1930 and 1960. Barnes and Pietruszka2 reported 10 cases that occurred at the Health Center Hospital of the University of Pittsburgh (Pa) between 1945 and 1976. Donegan3 found 18 cases at the Ellis Fischel State Cancer Hospital (Milwaukee, Wis) during a 26-year period, an incidence of 0.7%. Pollard et al4 reported 25 cases of breast sarcomas out of 500000 surgical specimens and approximately 11000 breast malignancies that were recorded between 1905 and 1990 at the London Hospital, an incidence of 0.3% of all breast malignancies. Of the reported tumors, malignant fibrous histiocytoma,4 liposarcoma,5,6 and fibrosarcoma3 appear to occur most frequently. The biologic behavior of these neoplasms depends on a number of histopathologic parameters (eg, microscopic contour of the tumor, degree of cellular atypia, and number of mitoses), as described by Norris and Taylor.7

Primary rhabdomyosarcoma of the breast is an extremely rare neoplasm. Of the reported cases only 2 have been adequately documented.1,8 Oberman1 described 3 cases of rhabdomyosarcomas, of which only 1 exhibited cross striations. Barnes and Pietruszka,2 Donegan,3 and Evans9 have reported 1 rhabdomyosarcoma each. In all 3 reports, no cytoplasmic cross striations were identified. The tumors are described as pleomorphic, and the diagnosis of rhabdomyosarcoma was made on the basis of cell pleomorphism and the presence of "strap" cells and "racquet" cells. It should be noted that the presence of "strap" cells and "racquet" cells is not sufficient evidence to classify an otherwise pleomorphic tumor as rhabdomyosarcoma, unless there is clear evidence of the rhabdomyoid origin of the neoplastic cells, according to established histopathologic criteria, and clear demonstration of typical cytoplasmic cross striations. In the absence of both of these characteristics, immunohistochemical staining or electron microscopic studies8 will help establish the true nature of the neoplasm. Neoplasms described as rhabdomyosarcomas may represent malignant fibrous histiocytomas, one of the most common nonepithelial cancers of the breast.4 It is a well-established fact that many of the previously reported cases of soft tissue pleomorphic rhabdomyosarcomas actually represented malignant fibrous histiocytomas, and these are recognized as such today.

The origin of primary rhabdomyosarcoma of the breast is obscure, and speculations abound. Misplaced mesenchymal rests, rhabdomyoblastic differentiation of tumors of mesenchymal origin, and pluripotential cells from periductal and acinar mesenchymal cells undergoing rhabdomyoblastic differentiation have been proposed. At present, the number of documented cases of breast rhabdomyosarcomas is too small to permit a critical discussion of their origin.

References

1. Oberman HA. Sarcomas of the breast. Cancer 1965;18:1233 1243. 2. Barnes L. Pietruszka M. Sarcomas of the breast: a clinicopathologic analysis of ten cases. Cancer. 1977;40:1577-1585.

3. Donegan WL. Sarcomas of the breast. In: Donegan WL, Spatt]S, eds. Cancer of the Breast. 3rd ed. Philadelphia, Pa: WB Saunders Co; 1988;689-715. 4. Pollard SG, Marks PV, Temple LN, Thompson HH. Breast sarcoma: a clinicopathologic review of 25 cases. Cancer. 1990;66:941-944.

5. Austin RM, Dupree WB. Liposarcoma of the breast: a clinicopathologic study of 20 cases. Hum Patho.'.1986;17:906-913. 6. Hummer CD Jr, Burkart Tl. Liposarcoma of the breast: a case of bilateral involvement. Am J Surg.1967;113:558-561.

7. Norris HJ, Taylor HB. Sarcomas and related mesenchymal tumors of the breast. Cancer. 1968;22:22-28.

8. Woodard BH, Farnham R, Mossler JA, Snell H, McCarty KS Jr. Rhabdomyosarcoma of the breast. Arch Pathol Lab Med. 1980;104:445-446.

9. Evans RW. Rhabdomyosarcoma of breast. J Clin Pathol. 1953;6:140-144. 10. Parham DM, Robertson AJ, Hussein KA, Davidson AIG. Leiomyosarcoma of the breast: cytological and histological features with a review of the literature. Cytopathology. 1992;32:985-990.

11. Waterworth PD, Gompertz RHK, Hennessy C, Henry JA, Lennard TWJ. Primary leiomyosarcoma of the breast. Br J Surg. 1992;79:169-170.

12. Muller AGS, Van Zyl Ja. Primary osteosarcoma of the breast. J Surg Oncol. 1993;52:135-136.

13. Ladefaged C, Nielsen BB. Primary chondrosarcoma of the breast: a case report and review of the literature. Breast. 1984;10:26-28. 14. Callery CD, Rosen PP, Kinne DW. Sarcoma of the breast: a study of 32 patients with reappraisal of classification and therapy. Ann Surg. 1985;201:527-532.

Accepted for publication March 18, 1998. From the Department of Pathology, New York Medical College, Valhalla.

Reprints: Andreas P. Kyriazis, MD, Department of Pathology, New York Medical College, Valhalla, NY 10595.

Copyright College of American Pathologists Aug 1998
Provided by ProQuest Information and Learning Company. All rights Reserved