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Editor,—Microcystic adnexal carcinoma (MAC) is a locally aggressive cutaneous tumour first described by Goldsteinet al in 1982.1 This tumour has a predilection for the face2 3 with only a few cases reported involving the periocular region.4-6 It is a low grade tumour of eccrine sweat gland derivation which behaves aggressively in its growth pattern and recurrence rate. It has also been known as a sclerosing sweat duct carcinoma (SSDC). We report a case of MAC initially masquerading as a benign chalazion.
A 66 year old white woman attended the accident and emergency department at the Western Eye Hospital with a 2 week history of red sore eyes. Bilateral blepharitis was diagnosed and a chalazion noted at the medial end of the left lower eyelid, adjacent to the punctum. The only unusual comment made was that the chalazion had “granulation tissue” on its conjunctival surface.
The blepharitis was treated with topical antibiotic and eyelid hygiene and she was listed for minor surgery. However, she had incision of her chalazion elsewhere and did not attend the accident and emergency department for another 18 months when she returned with recurrent symptoms of blepharitis.
On examination, a distorted reddened lower eyelid lump was observed in the exact location of her previous “chalazion” which had apparently remained despite incision. There was some puckering of the anterior lamella with radiating telangiectatic vessels suggesting that it was not a benign granuloma (Fig 1). It was nodular and fibrotic, affecting mainly the posterior lamella, and measuring 8 mm horizontally and 5 mm vertically. The tumour had surrounded the lower punctum and extended towards the medial canthal angle. There were no cilia overlying the tumour. There was no regional lymphadenopathy or periorbital anaesthesia.
An incisional biopsy (6 × 2 × 2 mm) of the involved posterior lamella (tarsal plate and conjunctiva) revealed a MAC (Fig 2). The tumour was subsequently excised completely by two layer Mohs’ micrographic surgery, which necessitated excision of the medial half of the lower eyelid, from the medial canthal angle. Reconstruction was by a Hughes’ tarsoconjunctival graft, with a free skin graft, with second stage division of the flap and reconstruction of the medial canthal angle 6 weeks later. The final eyelid appearance was satisfactory (Fig3) and she was not concerned about epiphora, although the lower canaliculus had been lost.
The patient’s past medical history was notable for systemic lupus erythematosus complicated by renal failure necessitating allograft renal transplantation with prednisolone and cyclosporine immunosuppression for 18 months before her initial presentation with an apparent chalazion.
The tumour was composed of narrow cords of cells with round or oval vesicular nuclei containing small eosinophilic nucleoli associated with a fairly dense fibrous stroma. Focal ductal differentiation was evident with occasional keratocysts present.
Microcystic adnexal carcinoma is a rare skin tumour which is becoming increasingly recognised. It may be mistaken clinically and histologically for other benign and malignant tumours.2MAC is a malignant sweat gland tumour and has a variety of synonyms which are now in disuse; sclerosing carcinoma of sweat ducts, malignant syringoma, sweat gland carcinoma with syringomatous features, and sclerosing sweat duct (syringomatous) carcinoma (SSDC).7Clinically it presents in the fourth to seventh decade of life with no sex predilection. Up to 90% of these tumours are facial.2 3
Wide excision by Mohs’ micrographic surgery is indicated3 8 as the tumour is locally aggressive with perineural, intraneural, and direct spread into adjacent dermis, subcutaneous tissue, muscle, periosteum, and bone.3 5 9Solid nests of dark or clear staining cells form nests, strands, or cords in a sclerotic stroma. Large biopsies are necessary for these features to be conserved for evaluation at low magnification; small biopsies have been shown to contribute to misdiagnosis.
The aggressive nature of MAC is not initially recognisable from its slow growth and benign clinical and histological appearance. It is more infiltrative with perineural invasion, than basal cell carcinoma.
Simple excision alone is insufficient as local recurrences are common (recurrence rate over 40%).2 3 7 Late recurrence has been reported, even 30 years after simple excision. Recurrences are greatly reduced with augmented excision and Mohs’ micrographic surgery.
This case of MAC differs from others in that it was mistaken clinically by several ophthalmologists for a chalazion. In addition, our patient had been immunosuppressed following renal transplantation, and it is conceivable that this had a role in its pathogenesis. The association of radiotherapy at a distant site and the development of MAC has been reported.10
In the past MAC has variably been thought to be derived from the hair follicle, the eccrine sweat gland, or even both. Nowadays, however, the tumour is firmly classified within the spectrum of eccrine sweat gland malignancies. A constant finding in this tumour is the presence of ductal differentiation which can be made more obvious with the periodic acid Schiff reaction or by EMA/CEA immunohistochemistry.11
Other malignant tumours occurring around the eyelids are summarised in Table 1. MAC is a rare tumour which may be differentiated clinically from other eyelid tumours by its slow growth, dense fibrous appearance, and slightly indistinct margin without skin ulceration. It is less common than sebaceous cell carcinoma which may also masquerade as a chalazion. Breast carcinoma metastases do occur in the eyelid and should be considered as a clinical differential diagnosis; however, the histological differential diagnosis does not include breast sweat gland carcinoma metastasis.
Clinicians should have a low threshold for submitting curettings for histopathology from any apparent chalazion which appears solid on incision. In particular, clinicians should be suspicious of solid recurrent chalazions, even if they have a benign clinical appearance which gives very little indication of the tumour’s identity and aggressive behaviour. If in doubt, we recommend a large incisional biopsy for histopathological diagnosis; then wide excision biopsy with Mohs’ micrographic surgery once the histopathology has been confirmed, to prevent recurrence.
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