Spindle cell metaplastic breast tumors display a range of elements, including low-grade tumors to those with areas of high-grade sarcomas like fibrosarcomas and malignant fibrous histiocytomas [2
]. Among these, a low-grade "fibromatosis-like" variant of a metaplastic carcinoma with only <5% tumor cells showing epithelial traits, has been a recently described entity [4
]. Identification of this variant assumes importance as, like fibromatosis, it has more chances for local recurrence than distant metastasis [4
]. At the same time its exact diagnosis from this close morphological differential i.e. fibromatosis and other benign and malignant spindle cell tumors has a far-reaching significance and requires application of IHC markers.
The present case observed in an elderly female who underwent a lumpectomy for a painless breast lump, exemplifies the diagnostic and management issues related to this tumor. The relatively bland nature of cells has prompted some authors to label it as a 'tumor' than a carcinoma [4
This tumor has predilection for older women. In a classical premier series of 30 exclusive cases by Gobbi et al
] and 24 cases by Sneige et al
], the average age seen with this tumor was 63.4 years and 66 years respectively. Gobbi et al
] identified these cases in women having a single palpable, generally painless, breast mass, more commonly in the left side (62.5%), as seen in our case.
On gross findings, they observed an average size of 2.7 cms with these tumors; mostly associated with unencapsulation and irregular borders [4
]. In the present case, the tumor displayed an irregular and an infiltrative growth pattern, both grossly as well as microscopically; thereby closing mimicked an aggressive mesenchymal tumor/sarcoma on the frozen sections. In view of predominantly spindle cells with mild atypia, however, revealing prominent infiltration into the adjacent soft tissues, diagnosis of a low-grade sarcoma was favored over a metaplastic carcinoma that seemed to be the closest differential diagnosis. An exact diagnosis was not offered since multiple section examination and adjunctive IHC application were anticipated for arriving at a final diagnosis. However, in view of a favored diagnosis of a low-grade sarcoma, the patient was spared for an ALND. On histology, the differential diagnoses considered were nodular fasciitis (NF), an inflammatory myofibroblastic tumor, pseudoangiomatous stromal hyperplasia (PASH), a myofibroblastoma, a low-grade fibrosarcoma and of course fibromatosis, which was a very close differential diagnosis. Nodular fasciitis (NF) and an inflammatory myofibroblastic tumor were ruled out based on the lack of conspicuous lymphoplasmacytic infiltrates and myxoid background [7
]. Absence of slit-like spaces lined by fibroblastic cells made a diagnosis of a pseudoangiomatous stromal hyperplasia (PASH) less likely. Lack of fascicular arrangements and lower cellularity helped to rule out a fibrosarcoma and pleomorphic sarcomas. [10
]. The immunoprofile was also helpful in objectively ruling out the other mentioned differential diagnoses, all of which lack epithelial expression. Thus it is imperative to employ a panel of epithelial and myoepithelial markers in spindle cell tumors of breast. Unlike Schafernak et al
], who noticed focal positivity for epithelial markers in the spindly cells, we observed a diffuse strong immunoreactivity in spindle and slightly more in plump cells as was observed by Gobbi et al
]. Among the various cytokeratins, a diffuse strong expression of HMWCK that is believed to be an expression of squamous carcinomas was suggestive for metaplastic traits of the tumor. Similar finding have been noted by others [4
]. As in our case, Gobbi et al
] demonstrated CK7 positivity, mostly in glandular areas in both their cases of predominantly "fibromatosis-like" carcinomas that were analyzed with IHC. A positive co-expression of epithelial and mesenchymal markers in the spindly cells might be considered as suggestive of 'epithelial-mesenchymal' transition observed with these tumors.
Positive expression for myoepithelial markers in this case is further suggestive that these tumors might constitute as myoepithelial subtypes of a metaplastic carcinoma. A positive p63 expression, like in our case, has been lately identified in 86.3% cases of myoepithelial carcinomas in a study by Koker et al
]. Ultrastructural findings further confirmed epithelial nature of these tumor cells with the presence of cell junctions and microvilli. Gersel et al
] described a series of spindle cell carcinomas of the breast including deceptively bland carcinoma cells.
Micropapillomas and papillomas have been described to be associated with an increased risk for subsequent development of a breast carcinoma and may form its antecedent lesion [13
]. Association of a micropapilloma with metaplastic carcinomas was also noted by Gobbi et al
]. However, the 'fibromatosis-like' pattern was noted in only a few of their cases [5
The optimal treatment options for this tumor remain unclear. However, most authors insist on a complete local treatment like lumpectomy with wide margins and adjuvant RT [4
]. Rarely, such cases, generally larger sized, with distant metastasis have also been identified by Sneige et al
] and Kinkor et al
]. Though the present case limits an ALND in view of less likeliness for nodal metastasis, currently, given the epithelial nature of this tumor, it would be worthwhile to perform a sentinel lymph node dissection in such cases.