Nonepithelial Malignancies of the Breast

Chugh and Baker have presented a concise and contemporary review of the common nonepithelial malignancies of the breast, focusing mainly on the management of this heterogeneous group of neoplasms. Needless to say, appropriate management of any neoplasm is entirely dependent on accurate pathologic diagnosis. Due to the rarity of these nonepithelial malignancies of the breast, they commonly present difficulties in pathologic diagnosis. Issues relating to the diagnosis of these tumors may not be obvious to nonpathologists, and deserve comment. Classification of Nonepithelial Malignancies of Breast
The stroma of the breast includes blood vessels, fibroblasts, smooth muscle, peripheral nerves, and last but certainly not least, adipose tissue. A complete list of all possible nonepithelial malignancies of the breast would be a lengthy one and would include angiosarcoma, fibrosarcoma, leiomyosarcoma, peripheral nerve sarcoma, and liposarcoma. Pathologic classification of these tumors remains problematic. One need only note that Chugh and Baker list malignant fibrous histiocytomas among the most common subtypes of breast sarcomas-however, the very existence of malignant fibrous histiocyto ma as a pathologic entity has been questioned.[1] The authors have classified nonepithelial malignancies of the breast into five basic categories: primary breast sarcoma, secondary (therapy-related) sarcoma, phyllodes tumor, primary lymphoma, and angiosarcoma. This classification may be helpful from a clinical perspective but is overly (and overtly) simplistic from a pathologic standpoint. For instance, primary breast sarcomas encompass a complex (and dizzying) array of tumors. Classification of these tumors may be dependent on the pathologist's understanding of histogenesis or differentiation. For example, liposarcoma in the breast is uncommonly primary and most often represents liposarcomatous differentiation in a malignant phyllodes tumor.[2] Clinicopathologic Correlation
The pathologist entrusted with the diagnosis of nonepithelial malignancies of the breast ought to possess all pertinent clinical information. The availability of clinical history, eg, previous sarcoma or radiation, is crucial for accuracy in diagnosis. Some nonepithelial malignancies in the breast could represent metastatic tumors. Radiation has been associated with certain stromal tumors including the so-called malignant fibrous histiocytoma. Information regarding physical examination and radiologic findings may be important in establishing the appropriate pathologic diagnosis. Cutaneous (from skin overlying breast) or osseous (from a rib underlying breast) neoplasms may simulate primary intramammary nonepithelial malignancies. Knowledge of the patient's clinical history is critical for the diagnosis of so-called "atypical vascular lesion"- a lesion described in the skin overlying the breast following irradiation.[ 3] These lesions may be difficult to distinguish from low-grade angiosarcomas. Clinical presentation as a discrete cutaneous lesion, a short interval between irradiation and presentation, and subtle histologic differences are helpful in establishing the apposite diagnosis. Phyllodes Tumor
As Chugh and Baker have indicated, the pathologic diagnosis of phyllodes (fibroepithelial) tumor must be qualified as benign, borderline, or fully malignant-a distinction determined by the tumor's cellularity, stromal overgrowth, mitotic activity, and cytologic atypia. However, the overriding determinant of prognosis is the assessment of margins: The fundamental goal of therapy for all forms of phyllodes tumor is complete excision to prevent recurrence. Second Opinion
Pathologic diagnosis of some forms of nonepithelial malignancies may be challenging. For example, a certain type of epithelial malignancy (metaplastic spindle cell carcinoma) may simulate a nonepithelial malignancy. As a matter of fact, this tumor has been referred to as a "fibromatosislike" carcinoma.[4] The diagnosis of this tumor may require confirmatory immunostaining with high-molecularweight cytokeratin, but above all else, requires awareness of the entity on the part of the pathologist. In terms of incidence, malignancies of epithelial origin vastly outnumber those of nonepithelial (stromal) origin-the latter comprise < 5% of all breast cancers. Owing to their rarity, nonepithelial malignancies are uncommonly encountered by pathologists in routine practice. Rare diagnoses require diagnostic affirmation by ancillary techniques, and may also require a second opinion from an expert well versed in the diagnostic nuances of such neoplasms.[5] Optimistic Note
A notable silver lining in the otherwise dark cloud of nonepithelial malignancies of the breast is the expectation that with the advent of sentinel lymphadenectomy, Stewart- Treves syndrome (ie, angiosarcoma primarily in the upper extremity following lymphedema) has been relegated to the pages of textbooks of medical history. Nonepithelial malignancies of the breast are uncommon. Accurate pathologic diagnosis, crucial for the management of this group of tumors, should always be based on clinical information.