The primary cutaneous mucinous carcinoma (PCMC) is an extremely rare malignant tumour that has its origin in the deep area of the eccrine sweat ducts(1). There are less than 200 cases mentioned in the literature(2,3). The tumour was reported for the first time by Lotzbeck in 1859, then described by Lennox et al. in 1952, and later by Mendoza and Helwig in 1971(4).
We present the case of a patient, C.E., aged 60, living in urban environment, who is hospitalized for epigastric pain that began 1 month ago. The patient denies personal pathologic or heredocolateral antecedents.
The clinical exam identifies a normoponderal patient, blood pressure =110/70 mmHg, pulse rate=70/min regularly, cardiovascular and respiratory balanced; the abdomen is sensitive to touch in the epigastric area. In these conditions a superior digestive endoscopy is done - normal esophagus, stomach - parietal hyperemia at antral level, pylorus, bulb - normal, and an inferior digestive endoscopy, with normal endoscopic appearance. The investigations are continued and a CT scan is done: space replacement formation that infiltrates the distal sternal region, the anterior abdominal wall with peritoneal and anterior mediastinal extension, peripancreatic and phrenic lymphadenopathy (Figure 1, and Figure 2).
A biopsy was made and the histopathologic result is mucinous adenocarcinoma, but the origin of the tumour was not established.
The investigations are continued with breast ultrasound, gynecological and cardiological exams - all normal, blood exams and tumour markers such as CEA, CA 19-9, CA 15-3, and CA 125 - also normal.
The immunohistochemistry shows CK 7 positive, CK 20 negative, Ki67 positive 5% and the result is low grade (G1) mucinous adenocarcinoma with cutaneous primary location.
Corroborating the clinical, paraclinical, imagistic, histopathological, immunohistochemistry data and the results of interdisciplinary exams, a differential diagnosis between primary mucinous carcinoma and mucinous carcinoma metastasis with another primary location was possible.
In January 2015 the patient began chemotherapy with Paclitaxel, Cisplatin and 5-FU, with good clinical and hemathological tolerability, and a total of six cicles were administrated, until April 2016. At the moment, the patient undergoes radiotherapy.
The primary cutaneous mucinous carcinoma (PCMC) is accepted as being a sweat duct derived tumour, classified as a malignant tumour with apocrine and ecrine differentiation(2). PCMC is more frequently found in males and it usually appears between the ages of 50 and 70. Anatomically speaking, the tumour is found especially at the neck and head, the eyelid being the most frequent location (41% of cases)(3). Other locations described in literature are: the scalp (17%), the face (14%), the armpit (9%), thorax/abdomen (7%), neck (2%), and ear (1%)(3,5). Mendoza and Hedwig made the first contemporary description of this eyelid-located tumour. Later, Wright and Font published the biggest study including 21 cases of eyelid-located PCMC. Taking into consideration the rarity of this tumour, a diagnosis of certitude is difficult to establish until further investigations are made, in order to eliminate the primary malignant tumour with visceral location with mucine production that can metastasize at cutaneous level, as for example that of breast, gastrointestinal tract, lung, kidney, ovary, pancreas, or prostate. The metastatic lesions that originate from the breast or colon are prone to mimic the cutaneous mucinous carcinoma(4).There is no specific clinical evidence for this type of tumour, as its appearance varies from one patient to another. The first clinical impression is that of a cyst, basal cell carcinoma, keratoacantoma, nevus, apocrine hidrocystoma, another location primary tumour metastasis and in certain circumstances the clinical differentiation includes vascular lesions as those found in the Kaposi sarcoma(5).
In affected patients, regional metastases occur at a rate between 5% and 15% and the distant ones between 2% and 7%. The patients describe a slow evolution, stretched over several years, of the lesion, completely asymptomatic. Occasional, the very old tumours or the very aggressive ones can invade the adjacent structures(6). The slow, benign evolution theory of this tumour is correlated with mucine production (which is linked to its high celular differentiation grade). Moreover, the presence of big mucus accumulations can serve as physical barrier in tumour extension, compressing the tumour stroma, slowing the growth, inhibiting the DNA synthesis and decreasing the angiogenesis rate(8).
Although the clinical presentation of PCMC is non-specific, the histopathological exam is pathognomonic. Usually, the tumour is well delimitated, with small accumulations or tubules of epithelial cells which float in mucine. Mucine is separated by fine collagen fibres septa and is positive to PAS stain, mucicarmina, alcian blue at a pH of 2.5 and colloidal iron. Mucine, same as sialomucine, was characterized as sialidase-labile. The cells are small, basaloid, vacuolated with eosinophilic cytoplasm. The cellular pleomorfism and the mitosis are rare(7). The differential diagnosis between skin metastasis of colorectal/breast adenocarcinoma or with another location mentioned before and PCMC is difficult, the histopathological exam being similar in both situations. Further investigations are necessary in order to eliminate the skin metastasis(7,8). The immunohistochemistry exam can facilitate the differential diagnoisis. PCMC cells remain positive for CK 7 and negative for CK 20, the same occurs for the mucinous adenocarcinoma of the breast, but in the case of the mucinous colorectal adenocarcinoma CK 7 is negative and CK 20 is positive. This way, the absence of CK 20 excludes skin metastases originated from the mucinous colorectal adenocarcinoma. The use of CK 7 and CK 20 with imunohistochemistry coloration facilitates the diagnosis of almost 50% of mucinous carcinoma with visceral location, easing the final diagnosis. Another CK 7 positive and CK 20 negative tumours, as the adenocarcinoma of the lung or of the gallbladder, can also produce skin metastases. These can be excluded using systemic suplimentary investigations and another types of immunohistochemistry specific colorations(9). Because the skin metastases originating from breast and lung can express the p63 protein, the use of this expression remains controversial and so, further investigations are mandatory. The cases of PCMC can be estrogen, progesterone and GCFDP-15 positive(8,9). Quereshi et al. suggest that the positivation of the cutaneous tumour for p 63/ CK 5/6 helps in excluding the skin metastasis with breast origin(8). In a complex analysis of the skin metastasis, Brownstein et al. discovered that only 6% of these were located at head and neck level(10). The treatment of PCMC imposes local surgical excision. Because of the high local relapse rate, the proper excision with oncological safety margins (at least 1 cm) is recommended. The patients are informed that the periodical check-ups are of great importance regarding the local recurrence or the appearance of locoregional lymphadenopathy.
PCMC is a rare malignant tumour that must be evaluated and treated correctly. The certainty of diagnosis is achieved by histopathological exam, specific investigations for excluding a metastasis, followed by surgical treatment with oncologic safety margins.
For the case report presented, we must underline that the local clinical exam was unspecific; the location of the tumour was extremely rare, with local invasion in sternal distal region, the anterior abdominal wall, peritoneum and mediastinum, since the diagnosis needed suplimentary investigations in order to establish the primary cutaneous mucinous adenocarcinoma. n