Adenoid cystic carcinoma (ACC) of the breast is a rare breast cancer variant and optimal management is unclear. Salivary gland tumors having the same histological pattern as ACC of the breast were first termed "cylindroma" by Billroth [2]. Although ACC of the breast can occur between 30 and 90 years of age, it is more common in women in the fifth and sixth decade of life [3]. Most patients present with a dominant breast mass tender to palpation [4,7]. Histologically, ACC has a unique distinctive biphasic pattern that consists of true laminate and pseudo- cystic spaces, true glands are lined by epithelial cells and pseudocysts are lined by myoepithelial cells.

ACC of the breast is a rare neoplasm accounting for 0.1% of all breast carcinomas [1]. It is of special interest because of its favorable prognosis and distinctive histological appearance [4]. Although ACC occurs predominantly in females, male patients have been described in the literature [9,10]. ACC most frequently presents as a tender breast mass, often in the subareolar area. Prognosis is more favorable in ACC as compared to other types of breast cancer as lymph node involvement and distant metastasis are uncommon. In contrast to the aggressive nature of the salivary gland tumors, ACC of the breast has a favorable prognosis. The reason for this difference is unexplained. As seen in our patient, most patients with ACC have a mass when first diagnosed [12] and pain is often the most common symptom [4,6]. Patients have been reportedly monitored for more than a year with just the symptom of breast pain before a mass or a radiographic abnormality is detected [12]. In this case, the patient complained of pain although the initial mammography and the USG were inconclusive. Pain is also seen in ACC of the salivary gland where the pain and the tenderness are attributed to perineural invasion by the tumor. However in our patient such invasion was absent. This has been described in other series as well [12]. Although ACC of the breast is most commonly subareolar in location, nipple discharge is an uncommon symptom in ACC [13], and was not seen in our patient. Most ACC are well circumscribed and firm. The diagnosis can be made on fine needle aspiration cytology [14,15]. The smears are highly cellular and contain extracellular spheres of metachromatic material surrounded by uniform cells with scant cytoplasm. The tumor is mostly well circumscribed in appearance and generally ranges from 1 to 5 cm in size [5]. Ro et al. suggested that ACC of the breast can be graded on the proportion of solid growth of the tumor and this was correlated with prognosis [16]. Grades proposed were 1 (no solid element); grade 2 (< 30 % solid element); grade 3 (>30% solid element). The proposed treatment was local excision for grade 1 tumors, simple mastectomy for grade 2 tumors and mastectomy with axillary node dissection for grade 3 tumors. Although calcification may develop in these tumors, only infrequently are they detected by mammography. In our patient the initial mammogram was inconclusive as screening mammography often misses the tumor. In another series only 4 of 22 patients detected radiologically [12]. Axillary lymph node metastases are rare in patients with ACC. Arpino et al. noted lymph node metastases in only 4 of the 182 cases collected from the literature [3]. Distant metastases are uncommon with only 14 cases having been reported, but when they occur they tend to do so without prior lymph node involvement. Hence a routine axillary LN dissection is not recommended [3].