BACKGROUND: Extramedullary plasma cells tumours are rare. Much more rarer is their occurance in the breast tissue. Our aim is to  report a single  case of this very rare lesion (at least from an African perspective) that we incidentally diagnosed histopathologically as a primary extramedullary lesion in a 53 year old woman.

CASE DEATILS: Clinical records of a 53 year old postmenopausal woman was referred from a secondary health centre to our clinic with a three weeks’ history of right breast lump were reviewed.

There was no associated pain, nipple discharge, weight loss or systemic symptoms nor was there a previous history of trauma or surgery to the breast. On examination: two discrete lumps measuring 3x2 and 2 x 1.5cm in the upper medial quadrant of the right breast were identified.  The lumps were firm, irregular in shape, not attached to the skin or underlying tissues. Tentative diagnosis of adenocarcinoma of the breast was made, with a differential as fat necrosis. A wide excision biopsy was done four days later for histology, after an inconclusive cytological examination of smear of which the result revealed plasmacytosis. The liver function test, Plasma proteins electrophoresis, electrolytes, urea, creatinine, bicarbonate and pelvic X-rays, and abdomino-pelvic ultrasonography were normal. Bence Jones proteins were negative in urine. Histology of bone marrow aspirate revealed scanty plasma cells. 

RESULTS: She received 20mg dexamethasone, 20mg adramycin, and 2mg vincristine intravenously and 200mg of alloperinol daily by mouth for three days before leaving by the 4th treatment day against medical advice for personal reasons.

CONCLUSION: This rare lesion should sometimes be considered as a differential diagnosis of a breast lump, as it does not differ from the common lesions clinically, especially in older women.