OBJECTIVETo study the clinical and morphological features as well as immunophenotype of tubulolobular carcinoma of the breast (TLC).

METHODSEight cases of TLC were retrieved from 97 cases of invasive lobular carcinoma between January 2005 and March 2010 in the Peking Union Medical College Hospital. The clinical features and pathologic findings were studied and immunohistochemistry was performed for the expression of ER, PR, HER2, p53, E-cadherin, CK34βE12 and CK8.

RESULTSAmong the breast cancer patients, the incidence of TLC was about 1.0% (8/880). The mean age of the patients was 59 years, with a range of 45 to 79 years. All patients were asymptomatic, with incidental finding of a mass in the breast on health examination. Common findings on sonography included a hypoechoic nodule with irregular shape and spiculated margin. Histologically, the small uniform tumor cells were arranged in a mixed pattern showing single cells, single-cell files or cords, small round to angulated tubules, and infiltrating lobular or targetoid patterns around ducts that were specific for classical invasive lobular carcinoma. Low or intermediate grade intraepithelial neoplasms which had similar cellular morphology with the invasive tumor often appeared in the periphery, including ductal carcinoma in situ, lobular carcinoma in situ and intraductal papillary carcinoma. Immunohistochemistry of the tumor cells showed intense reactivity to ER (7/8) and PR (8/8), but no reactivity to HER2 or p53. Both the tubules and single-cell file or cords expressed E-cadherin (7/8), CK34βE12 (5/8), and CK8 (8/8) with a uniform staining pattern. All patients underwent modified radical mastectomy and 2/8 patients had metastatic carcinoma in the axillary lymph nodes. Seven patients were followed up for 28 to 75 months and remained well, including one patient that had a new breast mass 60 months after surgery, but had no treatment up to now.

CONCLUSIONSTLC is a rare variant of invasive breast cancer and reveals mixed histologic features of both tubular and lobular carcinoma with common expression of E-cadherin, CK8 and CK34βE12. A better understanding of TLC would enable pathological diagnosis to be made reasonably and accurately.