Adenoid cystic carcinoma of the breast: Experience at a tertiary care centre of Northern India.

INTRODUCTION: Adenoid cystic carcinoma of the breast (breast-ACC) is a rare tumor with a favorable prognosis, despite its triple-negative status and special type of basal-like tumor for which scant population-based descriptive data exist. We sought to provide new population-based information on breast-ACC in India. Due to the paucity of the number of cases, the natural history of the disease is not fully understood. This study was undertaken to examine the clinico-pathological characteristics of the disease and to evaluate the outcome of surgical intervention in a tertiary referral care centre.

MATERIALS AND METHODS: A retrospective analysis of all patients diagnosed and treated for ACC Breast in our hospital over the past 10 years was carried out (2005-2015). A database of the characteristics of these patients was developed. In all, 14 patients were identified. The investigations performed included routine blood investigations, chest X-ray, bone scan and either an ultrasound or a CT scan.

RESULTS: During the time period of 10 years, of 2347 with breast malignancy admitted to our department, only 14 were diagnosed as having ACC (3.15%). All patients were women (100%). The patients had a median age of 60.7 years (range 37-81). The most common symptom was lump in the breast. Two patients (14.2%) presented with nipple and skin retraction and two patients (14.2%) were asymptomatic with the diagnosis made by an incidental finding on routine examination. The CT and/or magnetic resonance imaging (MRI) showed the typical features of carcinoma breast. All the 14 patients were taken up for surgery. Nine patients underwent Modified radical mastectomy and five patients underwent Breast conservation surgery. Axillary lymph node dissection was carried out in seven patients and sentinel lymph node biopsy in the remaining. Tumor cells had a characteristic histologic pattern of ACC of the breast. Perineural invasion was present in six cases.

DISCUSSION: ACC of the breast is a very rare malignancy, accounting for less than 0.1% of all breast neoplasms. It affects the left and right breasts equally and tumors arise irrespective of the breast quadrants. However, in about 50 percent of patients, lesions are found in subareolar region. Pain or tenderness described in the minority of cases has not been correlated with histologically-confirmed perineural invasion. ACC is categorized as a basal-like subtype of breast carcinoma. Most cases are macroscopically well-circumscribed. Occasionally, pink, tan, or gray microcysts are evident. A tumor typically consists of a dual-cell population of luminal and myoepithelial-basal cells which may be arranged in one or more of three architectural patterns: tubular-trabecular, cribriform, and solid-basaloid. There is no consensus on the optimal management for patients with ACC of the breast. Based on its indolent clinical course and favorable outcome, ACC of the breast is generally cured by breast-conserving surgery, such as wide excision or quadrantectomy with or without radiotherapy.

CONCLUSION: Breast-ACC among women is characterized by ER-negative/PR-negative expression, rare regional lymph node involvement, a favorable prognosis with excellent survival, and absence of associated cancers. These findings reinforce the importance of tailored treatments for breast-ACC and the apparent heterogeneity of basal-like breast cancers.