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Small primary cutaneous mucinous carcinoma mimicking an early basal cell carcinoma

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Small primary cutaneous mucinous carcinoma mimicking an early basal cell carcinoma
Paul Teng MBBS, James Muir FACD
Dermatology Online Journal 19 (3): 3

Queensland Institute of Dermatology Greenslopes, Queensland, Australia


We report an early case of primary cutaneous mucinous carcinoma in a male patient with chronic actinic damage. Dermoscopic features influenced the clinical decision to obtain tissue for histopathology, which in turn revealed characteristic strands and nests amidst mucinous stroma. Immunohistochemistry did not confirm cutaneous origin of the tumor; instead a full internal malignancy screen was required. Clinicians should be aware of this rare entity, which most commonly occurs on the head and neck, and give advice on appropriate further investigations and management.

Case report

A 66-year-old male patient attended a Dermatology clinic for routine skin examination. He is well known to the practice with a background of extensive solar damage and numerous non-melanoma skin cancers (NMSCs). A papule was noted on the right cheek (Figure 1), measuring 3 mm to 4 mm in size and was reported by the patient to be completely asymptomatic. On dermoscopy (Figure 2), the lesion appeared to be non-pigmented, cyst-like, and contained a network of fine serpiginous vessels, resembling micro-arborization typical of basal cell carcinoma (BCC). There was also surface scaling, which is less common in BCC. Differential diagnosis initially included basosquamous carcinoma, acanthoytic squamous cell carcinoma, and adnexal tumor.

Figure 1Figure 2
Figure 1. Arrow pointing to location of papule (inset) on the right cheek

Figure 2. Dermoscopic image of lesion

An excision was performed and the histopathology revealed a carcinoma comprising strands, nests, and occasional glandular structures. The glandular structures exhibited moderately atypical cuboidal to low columnar cells with frequent mitoses and apoptotic bodies in an abundant mucinous stroma (Figure 3). There was invasion to mid-dermis but lymphovascular or perineural infiltration were not identified. Immunostaining showed that the lesional cells were strongly positive for cytokeratin 7 and CAM 5.2 with focal apical/luminal staining for carcinoembryonic antigen (CEA) and epithelial membrane antigen (EMA). A diagnosis of cutaneous mucinous carcinoma was made. Clarification for the origin (either primary or secondary to skin) of the tumor via immunostaining to assess for a myoepithelial in situ component was performed, yielding a negative result.

Figure 3
Figure 3. H&E demonstrating glandular proliferation amidst abundant mucinous stroma

For this reason the patient required full malignancy screen, including referral to an oncologist who performed thorough clinical examination, hematological markers, and full body CT-PET scanning. These detected no evidence of systemic malignancy. Upper and lower endoscopies were not requested in addition, because the patient was completely asymptomatic. The final diagnosis was primary cutaneous mucinous carcinoma and definitive treatment was carried out via wide local excision. The patient remains well and free from any cutaneous or systemic symptoms 9 months after initial consultation.


Primary mucinous carcinoma (PMC) of the skin is a rare malignant neoplasm deriving from sweat glands [1]. It was first described by Lennox et al in 1952 and since then approximately 200 cases have been documented in the literature, mostly in case reports [1]. The estimated incidence of cases is 0.07 per million, and most frequently diagnosed in those between 50 and 70 years of age [2]. PMCs are most commonly seen on the head and neck, but there is a specific predilection for eyelids [3]. In fact, of the reported cases 30 percent are on the eyelids and 43 percent more were found elsewhere on the head and neck [3]. Rarely, tumors occur on the chest, axillae, extremities, and genitalia.

The tumor can present as a nodule, cyst, or ulcer. The reported size at time of detection can be in the range of 0.5 to 7 cm but is usually less than 3 to 4 cm [1]. On the eyelids, the average tumor diameter at detection is much smaller, 3.7 mm in one series [3]. This is a logical finding because patients are likely to present much earlier with any abnormality at this delicate location. The estimated size of the lesion in our case is 4 mm and apart from eyelid cases, it is one of the smallest recorded to date.

Features on dermoscopy, and the patient’s history of skin cancers, were influential factors in the decision to excise this tumor. With the exception of surface scaling, dermoscopy of our case demonstrated features strikingly similar to an early nodular or cystic basal cell carcinoma. This is also in contrast to the features in the case reported by Yoshida et al [4], which had a whitish network with light brown globules. The larger size of that lesion, the ethnicity, and skin type of the patient may have accounted for the differences.

Histologically, PMC is a well circumscribed dermal tumor characterized by large amounts of small cord-like or nest-like clusters of epithelial cells, amidst pools of extracellular periodic acid-Schiff-positive, diastase-resistant mucin [2]. Of significant importance is the exclusion of a mucin-secreting metastatic tumor to the skin [2]. Potential sites of primary disease include the breast, pancreas, stomach, colon, salivary glands, prostate, and ovaries. However, the breast and gastrointestinal tract are the most frequently implicated [5].

The literature to date suggests that primary mucinous carcinoma cannot be distinguished based on routine staining. Whereas immunochemistry may be helpful, no consistently differentiating panel has been identified as yet [5]. The immunohistochemical stains, which may be positive in primary cutaneous carcinoma, include low molecular-weight cytokeratins (CK 7, CAM 5.2), CEA, EMA, human milk factor globulins (HMFGI and II), gross cystic disease fluid protein (GCCDFP 15), S-100 protein, α-lactalbumin, TFF1 and 3 (mucous-associated peptides of the trefoil factor family), and estrogen and progesterone receptors [5, 6, 7]. All of these may also be positive in mucinous carcinoma of the breast [5].

The presence of a myoepithelial layer, representing an in situ tumor component, has been proposed to be confirmatory for the cutaneous origin of tumor [5]. The relevant stains for this include p63, actin, CK5/6, and calponin [5, 6]. However, myoepithelial cells are not identified in a significant proportion of cases [5], limiting general usefulness of the test.

PMC of the skin is noted to be a locally aggressive tumor with low metastatic potential [1, 2, 3]. Whereas previous studies have suggested local recurrence rates of approximately 33 percent, a Danish population study noted only 1 of 15 verified cases [1]. Chosen definitive treatment in our case was wide local excision. Nevertheless, standard excision and Mohs micrographic surgery have also been recommended [1, 2, 3, 7].

In summary, we have described a case of primary mucinous carcinoma of the right cheek. The final diagnosis was reached via early detection with dermoscopy, histopathologic exam (utilizing a number of special stains), systemic work-up to exclude underlying malignancy, and clinical follow up. Ex vivo distinguishing tests for tumor origins clearly need to be developed to reduce potentially unwarranted investigations for internal malignancy.


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3. Papalas JA, Proia AD. Primary mucinous carcinoma of the eyelid: a clinicopathologic and immunohistochemical study of 4 cases and an update on recurrence rates. Arch Ophthalmol. 2010 Sep;128(9):1160-5. [PubMed]

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7. Nosrati N, Maender JL, Coleman NM, Hsu S. Asymptomatic plaque on the face. Primary mucinous carcinoma of the skin. Arch Dermatol. 2008 Oct;144(10):1383-8. [PubMed]

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