Glycogen-rich clear cell carcinoma (CCC) of the breast is a rare neoplasm. It has an incidence of between 1.4% and 3% of all breast carcinomas.¹ The criteria used for the diagnosis of this tumour are that it consists predominantly of cells with clear and occasionally finely granular cytoplasm containing periodic acid Schiff (PAS) positive, diastase labile material in at least 90% of the tumour area.² This tumour is a distinct entity that has different morphological characteristics to ordinary breast carcinomas and shares some characteristics of clear cell carcinomas of other organs.² In this case report, we present a glycogen rich CCC of the breast with a solid papillary pattern. A panel of antibodies directed against cytokeratin 7 (CK7), CK10, CK14, CK17, CK18, CK19, CK20, CK5/6/18, CK8/18, high molecular weight cytokeratin AE3 (HMWCK AE3), high molecular weight cytokeratin 34βE12 (HMWCK 34βE12), the oestrogen receptor (ER), the progesterone receptor (PR), chromogranin (CR), S-100 protein, smooth muscle actin (SMA), vimentin, and carcinoembryogenic antigen (CEA) were applied to analyse the immunophenotypical profile of this neoplasm.

A 45 year old woman with a centrally localised mass in her left breast had undergone excisional biopsy. On macroscopical examination, the tumour was localised in a cystically dilated duct, it measured 3 × 3 × 2.5 cm, and had papillary projections and solid areas on cross section (fig 1A​1A).). Microscopical examination revealed that the tumour was composed of a combination of solid areas and papillary projections with fibrovascular cores and areas of invasion. More than 90% of the tumour cells had wide polygonal clear cytoplasm, distinct cell borders, round and central nuclei, and prominent nucleoli. Atypia and pleomorphism were conspicuous in some areas (fig 1B​1B).). There were foci of necrosis and abscess in the tumour and the whole tumour was embedded. Squamous or transitional differentiation and gland formation were not detected. The wall of the duct that the tumour originated from had granulation tissue and the epithelium was not evident. There was stromal invasion in the form of solid nests (fig 1C​1C).). There were no proliferative epithelial changes except for apocrine metaplasia in the adjacent breast tissue, which was confirmed by examination of the radical mastectomy material four months later. Neither residual tumour nor lymph node metastasis were observed in the radical mastectomy specimen. A detailed radiological and clinical survey did not reveal metastatic foci or other primary tumours. The patient has been followed for 27 months with no evidence of recurrence or metastasis.

Glycogen rich CCC is a rare tumour but it is the most frequent cause of clear cell morphology in breast malignancies.³ The tumour is composed of cells with polygonal clear cytoplasm, centrally localised hyperchromatic, round/oval nuclei, and prominent nucleoli. The cytoplasm of the neoplastic cells typically contains PAS positive, diastase labile granules and intracytoplasmic mucin production is also seen.⁴ The histopathological pattern of glycogen rich CCC of the breast may be well differentiated tubular, papillary, and/or solid, which may or may not be associated with an intraductal component.¹ This neoplasm has a tendency to form solid and papillary patterns.^3,4 To the best of our knowledge, only two clear cell breast carcinomas with a solid papillary pattern have been reported to date.^3,4 The case reported by Hull et al had separate areas of papillary and solid patterns and consisted of single layered cuboidal and columnar clear cells.⁴ The second case was an intraductal tumorous growth of 4 mm in diameter, sharing similar histopathological features with our case— namely, fibrovascular cores and multilayered solid tumour cells.³