Low-grade adenosquamous carcinoma. A variant of metaplastic mammary carcinoma.

The prognostic significance of metaplasia in mammary carcinoma has not been well defined. Pseudosarcomatous metaplasia reportedly has an unfavorable impact on survival. Squamous metaplasia may have less effect on outcome except for the high-grade spindle cell form, which is particularly aggressive. This report describes 11 patients with a low-grade variant of adenosquamous metaplastic carcinoma which has a distinctive combination of glandular and squamous differentiation. The average age of the patients was 59 years (range 42-76). The tumors measured 1.5-3.4 cm (average 2.3) and were grossly hard, tan-yellow, and infiltrative. Follow-up in seven cases treated at least 1 year ago averages 3.5 years (range 1-6 years). Four of eight patients treated by local excision alone developed recurrence in the breast in 1-3.5 years. Negative lymph nodes were found in five axillary dissections. There have been no recurrences after mastectomy performed as primary therapy or for recurrence in seven cases. These findings suggest that patients with the low-grade adenosquamous variant of metaplastic carcinoma have a favorable prognosis. They may be good candidates for breast conservation therapy, but this will require adequate excision followed by primary radiotherapy.