Unilateral Conjunctival in situ Squamous Carcinoma with Bilateral Conjunctival Chlorpromazine-Induced Secondary Melanosis Masquerading as in situ and Invasive Melanoma.

PURPOSE To describe the clinical and histopathological features of a 61-year-old male with a history of eczema, asthma and schizophrenia on long-term chlorpromazine medication, who developed a unilateral limbal tumour in association with bilateral melanosis. PROCEDURES The patient was referred for a routine cataract assessment, and an incidental pink gelatinous limbal lesion was detected on the left side, associated with bilateral speckled brown conjunctival pigmentation. The limbal lesion and brown pigmentation were biopsied. The tissue was fixed in standard buffered formalin and processed to paraffin wax, and sections were stained with haematoxylin and eosin. Tissue from the pigmented area was also processed for transmission electron microscopy. RESULTS The biopsy from the limbal lesion showed an in situ squamous carcinoma associated with prominent numbers of intra-epithelial eosinophils. The biopsy of the pigmented area showed bilateral melanosis without atypia. The latter was attributable to an increase in melanin production rather than to melanocyte hyperplasia. Melanophages were also present in the adjacent substantia propria. These pigment changes were entirely compatible with chlorpromazine-induced secondary melanosis. CONCLUSIONS This paper highlights the first documented occurrence of in situ squamous carcinoma with bilateral chlorpromazine-induced conjunctival secondary melanosis. This clinically masqueraded as in situ melanoma/primary acquired melanosis and invasive melanoma. Bilateral melanosis is rare, has many causes and, in this case, was drug induced. This highlights the importance of thorough history taking and illustrates that not all pigmented and amelanotic lesions are in situ melanomas, primary acquired melanosis or invasive melanomas. Lastly, atopy was a risk factor for the development of this in situ squamous carcinoma.