To the Editor:
In the December 2007 issue, Breiting et al1 presented a case of primary mucinous carcinoma of the skin (PMCS), wherein they discussed establishing the primary site of the tumor.
We recently observed a similar case of PMCS in a 68-year-old African black male who underwent excision of a polypoid skin-colored supraorbital mass. The tumor measured 64 × 38 × 32 mm and had a soft tan-white shiny gelatinous cut surface. Histology revealed typical features of PMCS including large regular lobules separated by thin fibrous septa, admixed with smaller cords of eccrine-like epithelial cells floating in abundant amorphous mucin. Lymphovascular invasion was seen, along with occasional psammoma bodies that were hitherto unreported in PMCS.
Immunohistochemistry revealed positive staining for CK7, gross cystic disease fluid protein (GCD-FP), and P63, whereas CK20 was negative. Clinical workup neither did not reveal any other possible primary sites in other organs nor was there any evidence of metastasis from the skin lesion to other sites. Breiting et al did not mention p63 in their report. Previous studies have shown that p63 is highly expressed in primary carcinomas of the skin as opposed to metastatic tumors, thus making it a useful addition to the panel of immunohistochemical markers in distinguishing the 2 tumor groups.2-4
Our case highlights the usefulness of p63 in establishing the diagnosis of PMCS. In this male patient, p63 proved extremely helpful in excluding metastasis to the skin particularly from the gastrointestinal tract, pancreatico-biliary tree, and lungs. The case reemphasizes the periorbital area as the commonest site for PMCS. The large size of this tumor, incomplete excision, and presence of lymphovascular invasion portend ominous tumor behavior and prognosis.5
Ahmed Kalebi, MBChB, MMed (Path)
Martin Hale, MBChB, FC Path (SA)
Department of Anatomical Pathology
Chris Hani Baragwanath Hospital University of the Witwatersrand and National Health Laboratory Services Johannesburg, South Africa
1. Breiting L, Dahlstrøm K, Christensen L, et al. Primary mucinous carcinoma of the skin. Am J Dermatopathol
2. Ivan D, Nash JW, Prieto VG, et al. Use of p63 expression in distinguishing primary and metastatic cutaneous adnexal neoplasms from metastatic adenocarcinoma to skin. J Cutan Pathol
3. Ivan D, Hafeez Diwan A, Prieto VG. Expression of p63 in primary cutaneous adnexal neoplasms and adenocarcinoma metastatic to the skin. Mod Pathol
4. Kanitakis J, Chouvet B. Expression of p63 in cutaneous metastases. Am J Clin Pathol
5. Jih MH, Friedman PM, Kimyai-Asadi A, et al. A rare case of fatal primary cutaneous mucinous carcinoma of the scalp with multiple in-transit and pulmonary metastases. J Am Acad Dermatol
. 2005;52(Suppl 1):S76-S80.