Primary Clear Cell Carcinoma of the Conjunctiva

Clear cell carcinoma is a rare variant of squamous cell carcinoma of the skin characterized by extensive cytoplasmic hydropic change.^1,2 These tumors tend to occur in the head and neck of elderly white men. Because the clear appearance of the cytoplasm is due to hydropic change rather than the accumulation of lipid, mucin, or glycogen, histochemical stain results are negative. Some of these clear cells have a “bubbled” cytoplasm and have been confused with sebaceous carcinoma.¹ To our knowledge, primary clear cell carcinoma on the conjunctiva has not been reported.

A 79-year-old man visited for continuation of care after changing residency. His ocular history was significant for a conjunctival tumor excised from the right eye 12 years earlier. The patient brought his medical records with him. The original pathologic interpretation was Bowen disease. After the tumor was excised, local recurrences developed 1 and 4 years later. Both were removed surgically and diagnosed as carcinoma in situ. The patient had not had an eye examination in several years.

On examination, corrected visual acuity was 20/150 OD. A papillomatous conjunctival tumor was at the limbus, extending from the 9-o’clock position to the 3-o’clock position (Figure 1). The anterior chamber was normal. Other than cataract, the remainder of the examination was noncontributory. There was no regional adenopathy.

The tumor was excised under local anesthesia with a visibly normal margin, and abnormal epithelium was removed from the cornea mechanically. The surgical bed and surrounding conjunctival margin were treated with cryotherapy.

When the tumor recurred 6 months later in the same location, it was excised with a partial sclerectomy; additional cryotherapy was applied. The patient died of heart disease 4 years later but never showed signs of local or regional recurrence.

The slides obtained from the primary tumor showed conjunctival intraepithelial neoplasia with scattered clear cells. The tumor had a papillary pattern of growth. Slides from the next 2 recurrences were not available.

The third recurrence had a papillary pattern of growth and showed full-thickness dysplasia (Figure 2A). In many areas, the cytoplasm of the dysplastic cells was vacuolated (Figure 2B). The clear cells stained negative with mucicarmine, alcian blue at pH 2.5, periodic acid–Schiff, and S-100 protein and positive for epithelial membrane antigen.

The fourth recurrence consisted almost entirely of moderately pleomorphic clear cells (Figure 2C). The cells stained negative with alcian blue at pH 2.5, periodic acid–Schiff, and HMB-45. Results of a frozen section with oil red O performed at the time of surgery were negative.

The phenomenon of cytoplasmic clearing is found in a variety of tumors arising from the epithelium, most of which demonstrate positive histochemical evidence indicating eccrine, follicular, melanocytic, or sebaceous cell lineage.^2-6 The diagnosis of primary clear cell carcinoma is made by excluding these specific entities as well as metastatic carcinoma.² The relationship of the clear cells to neoplastic conjunctival epithelium in our patient was evident in the first biopsy and became more evident in the third recurrence as the proportion of clear cells increased.

Too few cases of clear cell carcinoma of the skin have been reported to draw firm conclusions about its clinical behavior. Four of the 6 initially described tumors from the skin displayed rapid growth, and 1 patient died of metastatic disease.¹ The tumor in our patient demonstrated a propensity for local recurrence, had few mitotic figures, and during a 16-year period never showed any evidence of regional or distant spread. Until more information on the behavior of primary clear cell carcinoma of skin or mucous membranes is available, it should be regarded as locally aggressive and possibly lethal.

Correspondence: Dr Margo, PO Box 46218, Tampa FL 33646 (cmargo@hsc.usf.edu).

Financial Disclosure: None reported.