Solid Variant of Mammary Adenoid Cystic Carcinoma

The Korean Journal of Pathology 2007; 41: 424-6

Ji Eun Kwon∙Yoon Hee Lee Adenoid cystic carcinoma (ACC) is a rare type of breast carcinoma and this tumor makes up Ju Yeon Pyo∙Sang Kyum Kim less than 0.1% of all mammary carcinomas; ACC is known to show a relatively favorable prog- Byeong-Woo Park1∙Woo-Ick Yang nosis. Among a variety of microscopic growth patterns of mammary ACC, a solid variant is the rarest and this can cause diagnostic difficulties. We present here a case of a solid variant Department of Pathology, Brain Korea of mammary ACC that occurred in the right breast of a 40-year-old woman who was initially 21 Project for Medical Science, and diagnosed with invasive ductal carcinoma. We discuss the histological and clinical character- 1Surgery, Yonsei University Health istics of this case. System, Seoul, Korea

Received : May 14, 2007 Accepted : August 27, 2007

Corresponding Author Woo-Ick Yang, M.D. Department of Pathology, Yonsei University Health System, 134 Shinchon-dong, Seodaemoon-gu, Seoul 120-752, Korea Tel: 02-2228-1765 Fax: 02-2227-7939 E-mail: [email protected] Key Words : Carcinoma; Adenoid cystic; Breast

Salivary-type neoplasms such as adenoid cystic carcinoma biopsy specimen from a referring pathologist was invasive duc- (ACC) rarely occur in other organs and if they do, then this can tal carcinoma. Following rebiopsy at our hospital, the patholog- cause diagnostic difficulties. Primary mammary ACC is rare ic diagnosis was solid variant of mammary ACC with basaloid and it makes up less than 0.1% of all the breast carcinoma.1 His- features, and right modified radical mastectomy with axillary tologically, this neoplasm displays cribriform, tubular, trabecu- lymph node dissection was performed. lar and solid growth patterns by the combination of epithelial The tumor was mainly composed of variable sized solid nests and myoepithelial cells, and the prognosis is relatively favorable, or islands of basaloid cells with infiltrative margins (Fig. 1). Tra- which is contrary to ACC occurring in the salivary gland.2 Shin beculae and tubules were focally present while any cribriform and Rosen3 have recently described a solid variant of mammary pattern was not identified. The intervening stroma was densely ACC with basaloid features as a histologically distinctive entity hyalinized and focally myxoid. The most easily identified cells that has the potential for axillary lymph node metastases. The were basaloid cells; these were medium to large poorly differen- purpose of this report is to present a case of a solid variant of tiated cells with oval hyperchromatic nuclei and indiscernible mammary ACC that was predominantly composed of basaloid cytoplasm (Fig. 2). As other constituent cell types, small round cells, and we review its histologic and clinical characteristics. to ovoid or angulated dark cells resembling myoepithelial cells and cuboidal epithelial cells were identified. Frequent perineural invasion was found. There was no carcinoma metastasis in CASE REPORT the 17 dissected axillary lymph nodes. The tumor cells did not express estrogen receptor (ER) or A 40-year-old woman presented with pain in her right breast, neuroendocrine markers. S100 protein was expressed in most of and she had experienced this pain for three months. Mammary the basaloid cells as well as some of the ductular epithelial cells ultrasonogram revealed an ill-defined hypoechoic lesion in the (Fig. 3B). Alpha smooth muscle actin and smooth muscle myosin right subareolar area and the lesion measured 3.5 cm at its maxi- heavy chain were completely negative. Vimentin and P63 were mal dimension. The initial pathologic diagnosis of a needle core positive only in a few basaloid cells. CD10 was positive in some

424 Solid Variant of Mammary Adenoid Cystic Carcinoma 425

basaloid cells and in most of the small dark cells, while the duc- case.2,4 However, perineural invasion has rarely been noted in tular epithelial cells did not express CD10 (Fig. 3A). A positive ACC of the breast, which is contrary to the salivary gland tumors.4 reaction to c-kit was found in many of the basaloid cells. A lumi- Interestingly, our case presented with mastalgia and showed nal type cytokeratin (cytokeratin 8/18) and a basal type cytok- prominent perineural invasion and this finding may have caused eratin (cytokeratin 5) were not selectively expressed in the epithe- pain in our patient. lial and basaloid cells (Fig. 3B, C). The most important single criterion for the diagnosis of ACC is a biphasic cellular pattern, and several myoepithelial cells markers can be applied for the differential diagnosis.5 In addi- DISCUSSION tion, ER can be used as a useful marker because this tumor is regularly ER negative. The solid or basaloid type of ACC should The most common presentation of mammary ACC is a pal- pable mass that is frequently found in the subareolar area, and pain or tenderness is frequently associated, the same as in our

Fig. 2. Most of the solid nests are composed of basaloid cells, which have large oval and hyperchromatic nuclei, and indiscernible cytoplasm. Within the solid nests, cuboidal epithelial cells form Fig. 1. The tumor is composed mostly of variable sized infiltrative ductular structure with discrete lumen (headarrows) or abortive islands and nests. The stroma is markedly hyalinized. lumen (arrows).

A B C

Fig. 3. (A) CD10 positivity is noted not in ductular epithelial cells but in basaloid cells. (B, C) Cytokeratin 8/18 (B) and cytokeratin 5 (C) are expressed both in the luminal epithelial cells and basaloid cells. 426 Ji Eun Kwon∙Yoon Hee Lee∙Ju Yeon Pyo, et al. also be distinguished from neuroendocrine carcinomas. a greater propensity for axillary node spread than did the conven- Basaloid cells have been used with somewhat different mean- tional mammary ACC. However, there have been several reports ings in the morphologic description of ACCs, and this can lead showing contradictory results.1,2 So, accurate prognostication of to considerable confusion. In the cribriform and tubular types, a solid type of ACC needs further investigation with a larger basaloid cells have been used to describe small dark modified group of patients. myoepithelial cells.5 The basaloid type has been used as a syn- onym for the solid type in some reports of ACC, while other reports have described the basaloid and solid types as different REFERENCES ones.4,7 A recent report on the solid variant of mammary adenoid cystic carcinoma with basaloid features depicted the basa- 1. Lawrence JB, Mazur MT. Adenoid cystic carcinoma: a comparative loid cells as medium to large cells with round to hyperchromat- pathologic study of tumors in salivary gland, breast, lung, and cervix. ic nuclei and scanty, mildly eosinophilic cytoplasm.3 We per- Hum Pathol 1982; 13: 916-24. formed immunohistochemical staining to understand the nature 2. Cavanzo FJ, Taylor HB. Adenoid cystic carcinoma of the breast: an of the basaloid cells. Among the myoepithelial cell markers, analysis of 21 cases. Cancer 1969; 24: 740-5. smooth muscle actin and smooth muscle myosin heavy chain 3. Shin SJ, Rosen PP. Solid variant of mammary adenoid cystic carci- were not expressed in the basaloid cells. C-kit and CD10 were noma with basaloid features: a study of nine cases. Am J Surg Pathol expressed in a significant proportion of the basaloid cells, while 2002; 26: 413-20. vimentin and p63 were expressed in a few basaloid cells. So the 4. Rosen PP. Adenoid cystic carcinoma of the breast: a morphologically basaloid cells in our case expressed a limited degree of myoep- heterogeneous neoplasm. Pathol Annu 1989; 24 (Pt 2): 237-54. ithelial markers. Contrary to our expectation, a luminal type of 5. Lamovec J, Us-Krasovec M, Zidar A, Kljun A. Adenoid cystic carci- cytokeratin and a basal type of cytokeratin were not selectively noma of the breast: a histologic, cytologic, and immunohistochemi- expressed in the epithelial and basaloid cells. We also support cal study. Semin Diagn Pathol 1989; 6: 153-64. the suggestion that the basaloid cell is a somewhat primitive cell 6. Ro JY, Silva EG, Gallager HS. Adenoid cystic carcinoma of the breast. with the capacity for multidirectional differentiation.5 Hum Pathol 1987; 18: 1276-81. Ro et al.6 reported that mammary ACC with a higher propor- 7. Azumi N, Battifora H. The cellular composition of adenoid cystic car- tion of solid elements demonstrated a tendency for both recur- cinoma: an immunohistochemical study. Cancer 1987; 60: 1589-98. rence and metastases. Recently, Shin and Rosen,4 have also sug- gested that the solid variant of ACC with basaloid features had