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Chalazia, sebaceous gland carcinomas (SGCs), and intratarsal keratinous cysts (IKCs) are the 3 main mass lesions of the tarsus that have received clinical attention. SGC is an aggressive, malignant neoplasm that is especially notorious for masquerading as other benign and less malignant lesions, such as chalazion, chronic keratoconjunctivitis, basal cell carcinoma, or squamous cell carcinoma.
Clinical presentations of usual IKC include a yellowish-white, slow-growing, well-circumscribed, and round mass that usually fixed to upper tarsus, although rare bluish or translucent lesions have been reported.
Herein we introduce the first case of tarsal mass that was clinically diagnosed as IKC, but finally revealed as SGC.
A 55-year-old Korean woman presented with a 4-year history of a palpable nodule in her left upper eyelid. Her medical and ocular history were otherwise unremarkable. The nodule demonstrated slow growth over the preceding few months. Incision and curettage was repeated 3 times over the preceding 4 years, and the lesion recurred after incision and curettage.
Physical examination showed a nontender, nonerythematous, and blue-greyish firm nodule that was fixed to the underlying tarsus with mobile overlying skin (Fig. 1A).
As the mass was originated from tarsus and shared many morphologic characteristics with IKC, we provisionally diagnosed the nodule as IKC. Under local anaesthesia, the patient underwent partial full-thickness tarsectomy on her left upper eyelid. The lesion was about 6 mm and embedded in tarsus with a well-developed wall, representing defined circular demarcation (Fig. 1B). However, the pathologic examination demonstrated atypical dark, pleomorphic sebaceous cells with foamy, vacuolated cytoplasm and mitotic figures (Fig. 2A, B). Immunohistochemical stainings revealed positive carcinoembryonic antigen and negative epithelial membrane antigen stain (Fig. 2C, D). The findings were consistent with SGC containing cystic changes. Additional wide surgical excision was performed on her left upper eyelid.
Clinical differentiation of chalazion, SGC, and IKC is often challenging because they all arise from tarsus and can be similar in gross morphology. Histopathologically, however, each shows distinct features. Chalazion manifests as a chronic lipogranulomatous inflammation with a mixture of inflammatory cells, including neutrophils, lymphocytes, plasma cells, and eosinophils. IKC is lined with stratified squamous epithelium, abrupt keratinization (no granular layer), and an eosinophilic cuticle. The lumen contains abundant keratinous debris and is surrounded by thick fibrous wall. No adnexae, such as sebaceous lobules or follicles, are attached to the cyst.
By immunohistochemical staining, the inner lining of IKC reveals distinct expressions of carcinoembryonic antigen and epithelial membrane antigen such as cytokeratin 17. SGC is composed of irregular lobular masses with signs of invasion. The cytoplasm is pale, foamy, and vacuolated. This feature of foamy cytoplasm is seen only in SGC.
SGC can be composed of cells with varying degrees of sebaceous differentiation, and so it can exhibit various clinical and histopathological properties.
The treatment and prognosis of each entity are also different from each other. Chalazion may resolve with conservative managements like warm compression and lid hygiene. In select cases, incision and curettage may be beneficial. In case of IKC, incision and curettage is not an effective long-term treatment. Total removal of the lesion, including full-thickness excision of tarsus at the cyst’s base, is suggested for definitive treatment. On the other hand, SGC requires a much more aggressive approach, such as surgical excision with wide margins or orbital exenteration.
As mentioned earlier, SGC is a great mimicker. This masquerading feature often leads to delayed management with increased morbidity and mortality rates. Shields et al. reported that the diagnosis of SGC was suspected initially in only 32% of patients at first examination and in only 50% at histopathologic examination elsewhere.
Thus, it is essential to perform meticulous history-taking and to maintain a high clinical suspicion for SGC so as to accurately and promptly diagnosis the malignancy.
Referred from this case, IKC also should be included in the list of diseases under which SGC can masquerade mainly because both lesions are situated in the tarsus, and SGC could contain cystic portions as in IKC. Thus, greater awareness and clinical suspicion is crucial in diagnosing IKC in order to discriminate it from SGC.
Sebaceous carcinoma of the ocular region: a review.