Extremely rare presentation of soft tissue metastasis from carcinoma breast as a massive swelling of upper extremity

Soft tissue metastasis from any primary malignancy is considered very rare and a breast carcinoma metastasizing to soft tissue is still rarer. To the best of our knowledge, carcinoma breast with soft tissue metastasis to upper extremity is very uncommon with only six cases been reported in world literature till date and our case is the seventh such case in an 80-year-old female, previously treated for carcinoma right breast 15 years ago. The patient presented with progressive painful massive swelling of right upper arm measuring 21 cm × 17 cm, of 2 months duration. Histopathological examination of the swelling showed metastatic deposits from a poorly differentiated adenocarcinoma. Further immunohistochemical (IHC) analysis revealed tumor cells staining positive for estrogen and progesterone receptors while negative for HER 2-Nu, desmin, epithelial membrane antigen, CK7 and thyroid transcription factor-1 (TTF-1), suggestive of metastasis from a primary breast carcinoma. Only few case series and isolated cases reports have been published regarding any primary malignancy or breast carcinoma metastasizing to soft tissues. A thorough review of literature also reveals that our case is the largest soft tissue metastatic swelling from breast carcinoma ever reported. We hereby present this case with review of literature to highlight its extreme rarity, unusual presentation, clinicopathological characteristics and its overall prognosis.