Fig. 25.13 Mucinous carcinoma. A 59-year-old man with an erythematous biopsy site on the right upper lid below the brow

Only one case of MC treated by the Mohs micrographic surgical method has been reported [113]. In a case involving the external auditory canal, wide excision was followed by Mohs micrographic surgery to remove an MC [114]. Wide excision approach has a local recurrence rate of 41% [101]. These rare tumors could be ideal Mohs surgery cases due to low chance of metastasis. Its local aggressive behavior should call attention to potential boney involvement of scalp cases. Furthermore, since some MCs can involve significant portions of the scalp, the Mohs technique may aid in salvaging the remaining normal tissue. Cylindromas have been treated by Mohs micrographic surgery [115, 116]. More cases of MC are needed to establish Mohs micrographic surgery as a treatment modality.

Summary: Mucinous Carcinoma of the Skin

•Most common site is head, favoring eyelids.

•Is a low-grade-malignancy, slow-growing tumor that has a high local recurrence with low metastatic rate, and fatal outcomes are rare.

•Imperative to evaluate for metastatic source.

(see Fig. 25.13). Other sites of involvement include scalp, axilla, trunk, perianal, vulva, and foot. Most lesions arise on older individuals, mean age of 63 years, with range of 8–87 years [120]. They present as asymptomatic nodules, growing for months to years, ranging in size from 0.4 to 12 cm [121]. Ulceration is rare. Although complete data are not available, there is a slight predisposition for males. Interestingly, there is a higher than usual frequency in African-American individuals, compared to other sweat gland carcinomas of the skin [122]. MuC rarely metastasizes, but due to incomplete excision have a high local recurrence rate. Metastases are usually regional to lymph nodes [123] at a frequency of about 10%, and distant metastases are rare [124– 127], Death is unusual, but has occurred in patients with distant metastases.

Of significance, mucinous carcinoma can arise in other organs, and may metastasize to the skin from breast, gastrointestinal tract, lacrimal and salivary glands in vicinity of the paranasal sinuses/nose, lung (bronchi), renal pelvis, ovaries, and prostate [128]. Metastatic lesions are most commonly from breast and colon cancer. One must thoroughly evaluate for a source of metastasis, prior to arriving at the diagnosis of primary cutaneous MuC. Clinically, most metastatic lesions are within vicinity of the organ. Breast carcinoma rarely metastasizes to the eyelid or facial area, but favors chest region. Colorectal carcinoma tends to metastasize to the abdomen wall. Therefore, most mucinous carcinomas located on the facial area are likely to be primary lesions. However, it is imperative a thorough physical examination, appropriate blood work, and imaging studies be performed.

Histologically, MuC is a dermal tumor that is unencapsulated and can extend into the deep subcutaneous tissue. One finds collections of epithelial cells in large pools of basophilic mucin, separate by fibrous septae (see Fig. 25.14). The epithelial cells are small and cuboidal with eosinophilic or vacuolated cytoplasm. Mitoses are rare. Pleomorphism is variable. The epithelial cells may have a cribiform or

Mucinous carcinoma (MuC) of the skin is a rare cutaneous malignancy that was originally described by Lennox et al. in 1952 [117]. The tumor usually arises on the face [118–121], particularly the eyelids

positive, hyaluronidase resistant. It is also reacts to mucicarmine, alcian blue at pH 2.5, and colloidal iron. MuC can have local neuroendocrine differentiation [129] or resemble infiltrating breast carcinoma [130]. Immunohistochemistry reveals reactivity to

low molecular weight cytokeratins, epithelial membrane antigen, carcinoembryonic antigen, vimentin, and occasionally to S-100 [131, 132]. On histological grounds, separating MuC of the skin from metastatic tumor can be indistinguishable. Some factors in favor of primary cutaneous origin are presence of an in situ component and absence of CK20 staining [131, 133] (exclude colorectal carcinoma). One study suggests the combination of dirty cell necrosis and presence of epithelial cells with absorptive/goblet cell differentiation favors intestinal origin [134]. The histogenesis of MuC has not been established definitively; however, most favor an apocrine origin [135].

Treatment for MuC is wide excision with clear margins. Recurrences after surgical excision have been reported as high as 28% [120]. Since MuC is derived from the secretory coil of sweat glands in the deep dermis and subcutaneous fat, these tumors tend to be deep-seated, which may partially explain

inadequate margins. They tend to be widest at the deepest portion of tumor. The tumor can grow in a noncontiguous fashion, with tumor satellites occurring away from the main tumor. Often as one excises or takes a Mohs layer, you will encounter a thick, clear viscous material extruded from the lesion, which represents sialomucin. The use of Mohs micrographic surgery has been limited [136–142]. In our opinion, it would seem best suited for periocular MuC cases due to the technique’s tissue-spar- ing capacity to preserve anatomical function and aesthetics. There are 11 published cases describing the use of Mohs micrographic surgery (see Table 25.4). Most of the cases occurred in ocular region, and with a mean follow up of 33 months, had no recurrences. In one paper, immunohistochemistry was utilized to aid in examining the Mohs layer [140]. Radiation and chemotherapy regimens have not been successful [124].