Abstract
Purpose :
Primary cutaneous mucinous carcinoma (PCMC) is a rare, low-grade, neoplasm that usually affects the eyelid. The prognostic is generally favourable; although local recurrences are not uncommon. Because PCMC is indolent in comparison to visceral mucinous carcinomas (MC), it is imperative to rule-out metastatic disease from any PCMC. Whilst histopathologic features can help to distinguish PCMC from metastatic disease; a basic immunohistochemistry (IHC) panel consisting of Cytokeratin 7, 20 and GCDP-15 is recommended. The addition of p63, a marker of myoepithelial cells, is believed to be a positive indicator of PCMC. The current study aims to validate the specificity of p63 in identifying mucinous lesions of cutaneous origins.
Methods :
A total of eight lesions from six patients were included. Diagnosis was as follows: clinically and histopathologically proven PCMC of the eyelid (n=2) and scalp (n=1, +1 metastasis), mucinous cystadenoma (MA) of the eyelid (n=2, +1 recurrence) and of the orbit (n=1). Histopathological features were reviewed and a full IHC panel was performed (CK7, CK20, GCDP-15, p63).
Results :
Histopathological findings for PCMC are solid or trabecular clusters of cuboidal and columnar neoplastic cells with large, and pleomorphic nuclei surrounded by mucinous material. Concordant with its low-grade nature, the neoplastic process is often surrounded by normal fibrous tissue, but invasion is possible. MA shows mucin-producing cells lining a hyperplastic cystic wall and tends to display a lesser degree of atypia and fewer mitotic figures than PCMC.
The IHC panel (Table I) shows a typical cytokeratin profile, while P63 is positive in 2/4 cases of PCMC and in one orbital MA.
Conclusions :
Our results demonstrate a need for a reliable IHC panel to differentiate PCMC from visceral MC. As the cytokeratin profile and GCDP-15 are identical in both skin and breast, the differential is based on the p63 stain, which is helpful but not positive in all cases. Discerning well-differentiated PCMC from its benign counterpart may be challenging. Moreover, the recurrence from a well-excised MA suggest a lesion capable of malignant transformation. Benign mucinous lesions of the eyelids shall be considered as pre-malignant and require a close follow-up. Given the severity of visceral MC and the challenges in identifying the primary source of disease, a full systemic workup is recommended for all patients.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.