Not otherwise specified (NOS)-type breast sarcomas are primary sarcomas of the breast with no specific differentiation, that is, sarcomas that cannot be subclassified based on morphology and immunohistochemistry. Primary NOS-type sarcomas of the breast are very rare.1 NOS-type mammary sarcoma is one subtype of the pure mammary sarcoma, or stromal sarcoma, which is an older and broader synonym.
In general, pure mammary sarcomas are extremely rare, accounting for about 0.5–1% of malignant lesions of the breast and < 5% of soft tissue sarcomas. They may occur in young women and also in males.2–6 These are a heterogeneous group of malignant neoplasms of the spindle cells, arising from the interlobular mesenchymal elements that constitute the supporting mammary stroma.6–8 Excluded from this presentation are malignant lymphomas and malignant phyllodes tumours.
Early diagnosis is essential; however, this is not easy as the features consistent with malignant lesions of the breast are often absent.3,4,9 Metastasis usually occurs via haematogenous spread. Most authors agree that the main treatment for breast sarcoma is surgical extirpation.2,3,10,11 The role of adjuvant radiotherapy and chemotherapy is unclear and controversial.12
We report on the case of a 49-year-old diabetic woman who underwent surgical excision of a mass in the right breast 1 year after first presenting with this mass. She had undergone previous operations for an ovarian cyst and cataract. The breast mass was first investigated in a polyclinic, using ultrasound, which reported a rounded mass measuring 3 × 2 cm in the right lower inner quadrant, with a mixed echo pattern. This appeared likely to be benign in nature (Figure 1).
On examination, there was a 2 × 2 cm, soft to firm, mobile mass inferior to the areola of the right breast. There was no skin tethering, no nipple discharge and no palpable axillary lymph nodes.
A new preoperative ultrasound taken 1 year after the ultrasound in the polyclinic showed two masses in the right breast. One of these was a benign-looking 9.6 × 6.8 mm mass, described as a possible lipoma at the 10 o'clock position. The second was a solid and well-defined subareolar, hypoechoic mass measuring 18.3 × 9 mm. This was a possible intraductal papilloma found in the lower outer quadrant of the right breast, with no distal acoustic shadowing, no significant vascular flow detected using a colour Doppler technique and no axillary lymph nodes (Figures 2 and 3).
Surgical excision of the breast mass under general anaesthesia was advised, with perioperative frozen-section study of the specimen. The operation was performed within 1 week of the patient's presentation. The gross appearance of the mass excised from the lower aspect around the 6 o'clock position was irregular, with a rounded, well-demarcated area of necrosis, and the perioperative frozen-section examination of the specimen showed a suspicious spindle cell tumour. The cavity after local excision was drained using a suction-type tube drain.
The finalized histopathological study of all sections reported a tumour composed of proliferating spindle cells, with marked atypia, necrosis and a large number of mitotic figures, some of which were atypical. No recognizable mesenchymal differentiation was found despite thorough sampling. The tumour was very close to, and even impinged on, excision margins. A panel of immunostaining, including pancytokeratin, desmin, vimentin, actin, CD10, CD34, CD117, CD31, p63 and S-100 protein, failed to define sarcomatous differentiation. Features were consistent with high-grade mammary sarcoma (NOS-type) (Figures 4 and 5).
Unfortunately, the patient was unavailable for follow-up as she was travelling outside the country.
Purely sarcomatous tumours of the breast (with the exception of cystosarcoma phyllodes – by definition a fibroepithelial lesion – and lymphomas) are extremely uncommon,8 constituting < 1% of malignant breast tumours.2 Sex hormones (plus many chemicals that act as endocrine disruptors) may be involved in the carcinogenesis of soft tissue (and also visceral) sarcomas.13
As breast sarcomas are rare, and imaging methods to establish an exact diagnosis are inadequate, they often present a diagnostic challenge. Radiologists and clinicians may misdiagnose and merely monitor such tumours.4,5,9 The lesion in this case was viewed radiologically and interpreted as benign-looking more than once. This situation can clearly affect the surgeon's judgement and, consequently, the surgical planning. A recent study showed that primary breast sarcomas have imaging features that are not typically seen in infiltrating ductal carcinomas, and that a large, oval, hypervascular mass with indistinct margins should raise suspicion that a primary breast sarcoma may be present, and prompt biopsy.9
Although surgical intervention was carried out together with study of a frozen section, the latter was not indicative of malignancy. A preoperative fine-needle aspiration cytology or Tru-cut biopsy may be diagnostic, as a review of previous studies has stated that these are reliable for diagnosis of sarcoma in the same way as for carcinoma.2 Appropriate immunohistochemistry is essential for differential diagnosis.5
Axillary dissection was not carried out in this case. Lymphatic spread is common in carcinoma, but rare in sarcoma. Lymph nodes were histologically involved in only 1 out of 39 axillary dissections performed in a French study, and in 2 of 22 dissections at Mayo Clinic, MN, USA.14,15 Recurrence rates and overall survival are not affected by the extent of surgery.15 Furthermore, the majority of stromal tumours of the breast are not multicentric.
Local recurrence of the lesion is common, and some studies advise mastectomy together with excision of the underlying pectoral muscle for better local control.2 Chemotherapy has been disappointing in the treatment of breast sarcoma,2 and, as such tumours do not appear to display hormone receptors, hormonal manipulations have no place in their treatment.
In conclusion, any breast lesion should be treated with a high degree of suspicion, even when the clinical findings and radiological features are reassuring. Such a presentation may, unfortunately, belie an aggressive tumour.