To the Editor:
Primary mucinous carcinoma of the skin (PMCS) is a rare, malignant neoplasm, most commonly occurring in the periorbital area. The tumor deserves attention not only for its rarity but also for the problems of differential diagnosis with dermal metastasis from mucinous adenocarcinoma of other sites. We present a case where a cutaneous metastasis from a primary breast carcinoma was suspected.
A 72-year-old white woman presented with a 4-year history of an asymptomatic tumor on the left side of the scalp. Physical examination showed a dome-shaped, skin-colored nodule measuring approximately 2 cm. At excision, a jellylike mass was found subcutaneously.
The histopathology showed a round tumor, with uniform, epithelial cells in small glands or islands with a solid, microglandular, or cribriform pattern, all floating in an abundant, mucinous substance separated by thin fibromuscular septa (Fig. 1). No in situ elements were found. The epithelial cells contained uniform, round nuclei that varied in size and that showed a few mitotic figures. The tumor cells were 80% estrogen receptor positive, 50% progesterone receptor positive, and 100% positive for cytokeratin-7. No actin or S-100 protein-positive myoepithelial cells were found. The microscopic diagnosis was mucinous carcinoma; because of its immunohistochemical profile, a cutaneous metastasis from a primary breast carcinoma was suspected.
Thorough clinical investigation, mammography, sentinel node biopsy, and chest radiograms secured the absence of regional or distant spread and ruled out a primary cancer of any other site, and it was concluded that the tumor was primary.
A 10-mm reexcision was performed to secure free margins. At 3-year follow-up, there were no signs of locoregional recurrence.
In summary, PMCS is a slow-growing carcinoma of the sweat glands and is often mistaken for a secondary tumor from a breast, ovary, lung, prostate, or gastrointestinal cancer. Local recurrence occurs frequently, but the tumor rarely metastasizes. Metastatic spread and ensuing death have only been reported in three cases.1-3 Clinical characteristics of previously reported cases are given in Table 1.1-7
Histologically, PMCS is usually described as a tumor consisting of islands of epithelial cells floating in pools of extracellular PAS-positive, diastase-resistant mucin4 (Fig. 1). An associated in situ component within the tumor may help in establishing the diagnosis. The histopathologic clue to an intestinal origin is the combination of dirty necrosis and the presence of epithelial cells with absorptive/goblet cell differentiation,5 just as tumors of the breast PMCS may contain PAS-positive, diastase-resistant sialomucin and express low-molecular weight cytokeratins (cytokeratin-7, CAM 5.2), carcinoembryonic antigen, epithelial membrane antigen, human milk factor globulins, gross cystic disease fluid protein, S-100 protein, alpha-lactalbumin, TFF1 and 3 (mucous-associated peptides of the trefoil factor family), and estrogen and progesterone receptors.6
Even though the factors mentioned above may help in establishing the primary site of the tumor, a final diagnosis only can be drawn when the patient has been subjected to a thorough investigation that excludes the presence of a more common primary mucinous carcinoma of the breast, lung, gastrointestinal tract, gall bladder, prostate, or ovary.
The recommended treatment of PMCS varies from standard excision to wide local excision,4 including dissection of the regional lymph nodes. It is recommended that the patient be controlled at least yearly, because of the risk of recurrence, and because the possibility still exists that the tumor, in the lack of in situ elements, might represent a metastasis.
Line Breiting, MD
Karin Dahlstrøm, MD
Department of Plastic Surgery Herlev Hospital, Denmark
Lise Christensen, MD, DMSc
Department of Pathology Bispebjerg Hospital, Denmark
Jeanette Falck Winther, MD
Institute of Cancer Epidemiology Danish Cancer Society Copenhagen, Denmark
Vibeke Breiting, MD
Clinic of Plastic Surgery, Holte, Denmark
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2. Rao KV, Tikku I, Kapur BM, et al. Invasive primary mucinous carcinoma of the skin. Int Surg
3. 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.
4. Snow SN, Reizner GT. Mucinous eccrine carcinoma of the eyelid. Cancer
5. Kazakov DV, Suster S, LeBoit PE, et al. Mucinous carcinoma of the skin, primary, and secondary: a clinicopathologic study of 63 cases with emphasis on the morphologic spectrum of primary cutaneous forms: homologies with mucinous lesions in the breast. Am J Surg Pathol
6. Hanby AM, McKee P, Jeffery M, et al. Primary mucinous carcinoma of the skin expresses TFF1, TFF3, estrogen receptor, and progesterone receptors. Am J Surg Pathol
7. Martinez SR, Young SE. Primary mucinous carcinoma of the skin: a review. Internet J Oncol
[serial online]. 2005;2:432-437. Available at: http://www.ispub.com/ostia/index.php?xmlFilePath=journals/ijo/vol2n2/skin.xml
. Accessed September 10; 2007. A full list of reference is available with the author.