INTRODUCTION: Primary breast sarcoma (PBS) was first described in 1887 as a rare heterogeneous neoplasm arising from the mesenchymal tissue of the mammary gland accounting for less than 5% of all body soft-tissue sarcomas and less than 0.1% of all malignant tumors of the breast. CASE PRESENTATION: A 31-year old lady presented with left breast mass which she felt four years before during which the mass increased in size from 1 to 6 cm in the largest diameter, diagnosed clinically as a benign fibroadenoma without any further cytological or histopathological confirmation. Histopathological examination of the excised breast mass reveals undifferentiated, primary stromal sarcoma of the breast (PSSB), which was followed by mastectomy three weeks later with reconstructive breast surgery with a total duration of follow-up of 3 years thereafter. This is the first case of PSSB reported in Jordan. DISCUSSION/CONCLUSION: PSSB is the generic term given to malignant breast tumors thought to arise from the specialized mesenchymal stroma of the breast but lacking an epithelial component with a phylloides pattern. PSSB is difficult to diagnose preoperatively due to its rarity and inadequate imaging methods to establish an exact diagnosis. The histology of the patient mass may be the leading factor for the management of these tumors. Even in very young patients, a progressively growing breast mass should alert the clinician to investigate for malignancy and verify the results by biopsy. Surgery with adequate resection margins represents the only potentially curative modality with prognostic significance. Adjuvant chemotherapy and radiotherapy are not very beneficial. The prognosis is dismal for patients with lymph node involvement and the size of the tumor has a lesser bearing on the outcome.

Highlights Primary adenocarcinoma of appendix is rare pathology that is discovered usually on histopathologic examination of resected appendix. It is important to report all pathologic reports to the primary physician in order to confirm primary diagnosis and discuss it with their patients. If a diagnosis of PAA is reported, a surveillance lifelong colonoscopy screening is mandatory to rule out synchronous or metachronous occurrence of colonic malignances.