Glycogen-rich clear cell carcinoma of the breast is a rare tumor. It is, however, the most frequent cause of clear cell morphology in breast malignancies [5
]. It is composed of cells containing abundant glycogen, which is extracted when the tissue is processed for histological sections, leaving vacuolated cytoplasm. Extraction of the cytoplasmic components also occurs in lipid-rich carcinoma, signet-ring cell carcinoma and in some secretory variants of ductal or lobular carcinomas, as well as sebaceous, myoepithelial and endocrine tumours [5
]. Cells with clear, vacuolated cytoplasm have been rarely found in benign breast lesions, such as clear cell hindradenoma, eccrine spiradenoma, acrospiroma and benign mammary myoepithelioma [4
]. These are only known as isolated case reports.
Signet-ring carcinomas frequently coexist with ductal or lobular carcinomas and display an aggressive course with frequent lymph node and distant metastases [6
]. Lipid-rich carcinomas tend to occur in elderly women as pure lesions, often involving axillary lymph nodes and have been occasionally reported to metastasize to the eyelid [7
]. Secretory carcinomas frequently arise in young women, but rarely metastasize to axillary lymph nodes [8
Clear cell neoplasms arise throughout the body. The vacuolated cytoplasm in many of these tumors can be attributed to large quantities of glycogen, as in clear cell carcinomas of the vagina, cervix, endometrium, ovary and salivary glands. The clear cell in renal adenocarcinoma contains not only glycogen, but abundant fat, both of which contribute to their optically clear quality [9
]. In the lung, two clear cell tumors are known: the benign clear cell (sugar) tumor, which contains abundant glycogen [10
] and the clear carcinoma, which contains abundant mucin [12
]. Clear cell carcinoma of the larynx, a variant of mucoepidermoid carcinoma, gains its clear cell features from both intracytoplasmic glycogen and mucin [13
]. In the thyroid, some clear cell carcinomas contain abundant colloid material [14
], while others contain abundant glycogen [15
]. Thus, the subcellular determinants of the clear cytoplasm vary from case to case.
Fewer than fifty cases of glycogen-rich clear cell carcinoma of the breast have been described since the first case was reported in 1981 [3
]. The patients, aging from 35 to 78 years, presented with a mass that was sometimes accompanied by skin dimpling, nipple retraction or pain. Most tumours reported measure between 2 and 5 cm in diameter, with the largest lesion found to be 10 cm on clinical examination [3
]. Hormone receptor analysis revealed that about 50% of the tumors were estrogen receptor positive, but all lesions studied, including our patient, have been negative for progesterone receptor. When analysed by flow cytometry, the tumors have been nondiploid [2
Almost all patients were treated with mastectomy and axillary dissection and more than half had metastatic tumour in the axillary lymph nodes [3
]. Our patient found to have negative axilla, despite the large size of the primary tumour.
The prognosis of glycogen-rich clear cell carcinoma of the breast is reported to be not particularly favorable and may be similar to or worse than that of ordinary invasive ductal carcinoma, when compared on a stage-matched basis [5
]. However, in the case reported here, the patient had a history of at least 4 years with a slow growing clear cell carcinoma of her breast. The tumour had benign features on mammography and the well circumscribed appearance was suggestive of fibroadenoma. No axillary lymph node involvement was found and there was no evidence of systemic disease in staging investigations. The only pathologic finding before surgical treatment was elevated levels of Ca 15-3, which dropped to normal following operation. Our patient, staged T2N0M0, is free of disease 48 months now and continues adjuvant therapy with an aromatase inhibitor only.