Metaplastic breast tumors exhibit a wide morphologic spectrum, ranging from tumors with clearly visualized epithelial elements to heterologous tumors with non-epithelial elements like spindle cells, cartilage and bone 1234. With the help of immunohistochemical (IHC) markers, different morphologic entities within the larger group of metaplastic tumors have been identified. Among these is an unusual, "fibromatosis-like" metaplastic carcinoma. Currently, there is a limited understanding for this tumor as a result of its rarity 45. We present a case of a "fibromatosis-like" metaplastic carcinoma associated with a micropapilloma in an elderly lady. This rare case is discussed to highlight its diagnostic and management issues.

A 77-year-old lady presented with the complaints of a left-sided breast lump of 1-month duration. She had been a heart patient and had been on treatment for the last 4 years. On clinical examination a 3 × 2 cm firm, mobile, non-tender lump was identified in the outer quadrant of her left breast. The overlying skin of the breast along with nipple and areola were unremarkable. There was no significant axillary or cervical lymphadenopathy. The other breast was normal. She underwent a mammographic examination, followed by fine needle aspiration cytology (FNAC) that was essentially inconclusive. Subsequently, she underwent a frozen section for a primary diagnosis.

On mammography, a 2 × 2 cm ill-defined mass with irregular margins was identified in the left upper outer quadrant. No micro-calcifications were seen. The right-sided breast was normal. (Figure 1).

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 234. 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 45. 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 4 and 24 cases by Sneige et al 6, the average age seen with this tumor was 63.4 years and 66 years respectively. Gobbi et al 4 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 789. 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 11, 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 4. 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 47. As in our case, Gobbi et al 5 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 12. Ultrastructural findings further confirmed epithelial nature of these tumor cells with the presence of cell junctions and microvilli. Gersel et al 3 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 5. 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 6 and Kinkor et al 14. 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.

An objective identification of this uncommon tumor with the help of a panel of IHC, along with the presence of a micropapilloma makes this case unique. Further, an uneventful follow-up for more than a year, despite avoidance of an axillary lymph node dissection suggests a relatively lesser metastatic potential of this tumor. A certain degree of index of suspicion in the pathologists' mind while dealing with spindle cell tumors of breast is helpful in making this diagnosis. Documentation of more of such cases with follow-up details would bring new light to the management and biological behavior of this unusual breast tumor.

The author(s) declare that they have no competing interests.

BR: Involved in the diagnosis of the case; design, preparation and drafting of the manuscript.

TMS: Involved in the diagnosis; preparation of the manuscript and in the ultrastructural analysis.

RDB: Treating breast oncosurgeon, provided the clinical and follow-up details.

RFC: Overall supervision and has given the final approval of the manuscript.