Sir,
An epidermoid cyst is a benign cyst of pilosebaceous origin. It is most commonly located on scalp, back and trunk. It was formerly known as cyst of follicular infundibulum, epidermal inclusion cyst or sebaceous cyst. Its occurrence in breast parenchyma is rare.
We report a case of a 21-year-old unmarried female who presented with a solitary, firm, mobile lump, approximately 3cm in diameter, in the upper outer quadrant of left breast. The lump was free from the overlying skin and was mobile over the underlying structures. Clinically, a provisional diagnosis of fibroadenoma was made. Ultrasonography revealed a well-defined homogenous echogenic mass lesion within the breast parenchyma, free from overlying skin, suggestive of a fibroadenoma. Fine needle aspiration yielded moderate amount of pultaceous material and Giemsa-stained smears showed numerous anucleate and nucleate squames rendering the diagnosis of an epidermoid cyst [Figure 1].
Figure 1.
Aspirate smear from breast lesion showing numerous anucleate and nucleate squames (Wright's Giemsa, ×100)
The pathogenic mechanisms of such cysts originating in the breast are poorly understood. They are believed to arise by various possible mechanisms. These include derivation from a congenital anomaly arising from cell nests remaining from the embryonic mammary ridge; as a sequel to traumatic or surgical changes, such as core needle biopsy or reduction mammoplasty, which may cause implantation of epithelium or the stimulation of epithelial proliferation; or as squamous metaplasia within an area of fibrocystic change or within a fibroadenoma.[1,2]
Epidermoid cyst in breast is an uncommon lesion, its rarity accounting for it being erroneously misdiagnosed as carcinoma or a benign lesion like fibroadenoma. In Australia, only two cases of epidermoid cyst were noted over a 3-year period from a mammography screening programme with 57,954 examinations.[1] Only few case reports have been described in the literature.[3,4] To the best of our knowledge, even after extensive review of literature, we did not find a case where the diagnosis was first made on fine needle aspiration cytology.
Importance of recognizing this lesion lies in the fact that it can be mistaken for any benign or malignant lesion of the breast both clinically as well as radiologically. Classically, radiologically epidermoid cyst gives an onion ring appearance of alternating concentric hyperechoeic and hypoechoeic rings at sonography, representing multiple layers of keratin. The true incidence of malignant change in epidermoid cysts is not known, although it may occur rarely.
Fine needle aspirate cytology serves a simple, yet efficient tool in diagnosing this lesion for which simple excision is curative.
References
- 1.Morris PC, Cawson JN, Balasubramaniam GS. Epidermal cyst of the breast: detection in a screening programme. Australas Radiol. 1999;43:12–5. doi: 10.1046/j.1440-1673.1999.00618.x. [DOI] [PubMed] [Google Scholar]
- 2.Chantra PK, Tang JT, Stanley TM, Bassett LW. Circumscribed fibrocystic mastopathy with formation of an epidermal cyst. Am J Roentgenol. 1994;163:831–2. doi: 10.2214/ajr.163.4.8092018. [DOI] [PubMed] [Google Scholar]
- 3.Lam SY, Kasthoori JJ, Mun KS, Rahmat K. Epidermal inclusion cyst of the breast: a rare benign entity. Singapore Med J. 2010;51:e191–4. [PubMed] [Google Scholar]
- 4.Taira N, Aogi K, Ohsumi S, Takashima S, Kawamura S, Nishimura R. Epidermal inclusion cyst of the breast. Breast Cancer. 2007;14:434–7. doi: 10.2325/jbcs.14.434. [DOI] [PubMed] [Google Scholar]