Syringoid eccrine carcinoma (SEC) is a very rarely diagnosed tumor. It is locally very invasive, destructive and often shows recurrences. Metastasis in the regional lymph nodes is extremely uncommon as are disseminated metastasis1. It was first described as eccrine epithelioma (basal cell carcinoma with eccrine differentiation) by Freeman and Winkelmann2 in 1969 and SEC has been called diverse synonyms including eccrine epithelioma, malignant syringoma, sweat gland carcinoma with syringomatous features, squamoid eccrine ductal carcinoma, syringomatous carcinoma, eccrine carcinoma and sclerosing sweat duct carcinoma3.

SEC most often present in the fourth to seventh decade of life and present as a solitary, firm nodule or plaque on the head, neck and less commonly trunk4. To the best of our knowledge, while only 9 cases of SEC were located on the extremities5678910.

A 94-year-old male patient visited our clinic with an 80-year history of a lesion on his left thigh. Physical examination revealed a 2×2 cm sized well-demarcated round shaped erythematous to pinkish nodule with an ulcerative cutaneous lesion on the left thigh (Fig. 1). Personal and family medical history was unremarkable. Routine laboratory tests were either normal or negative except elevated eosinophil level (15%) and erythrocyte sedimentation rate (36 mm/h). Histological findings from the first punch biopsy of skin lesion on the left thigh revealed many atypical infiltrating glands from superficial to deep dermis. Some ductal structures showed tadpole appearance and were consisted of anaplastic cell with deep basophilic nucleus (Fig. 2). Positive S-100, epithelial membrane antigen (EMA), cytokeratin (CK)7, focal positive carcinoembryonic antigen (CEA), Ki-67 level of less than 10% and negative reactivity to the transcription factor-1, prostate-specific antigen, CK20 were noted immunohistochemically (Fig. 3). The histological diagnosis was SEC. Computed tomography scan indicated a 1.3 cm×2 cm×3 cm sized triangular shaped focal soft tissue lesion in subcutaneous fat layer and dermis layer of the lesion and didn't show any metastasis to other organs. After diagnosis and evaluation of the tumor, the patient was treated with local wide excision. The histopathological results of excised specimen showed the same result of biopsy specimens. The patient didn't show any recurrence during the follow-up period of 12 months.

SEC is an extremely rare malignant adnexal tumor of eccrine origin, first described by Freeman and Winkelmann2 in 1969 and has been described under diverse synonyms: eccrine epithelioma, malignant syringoma, sweat gland carcinoma with syringomatous features, squamoid eccrine ductal carcinoma, syringomatous carcinoma, eccrine carcinoma and sclerosing sweat duct carcinoma3.

Primary eccrine carcinomas are rare tumors and make up less than 0.01% of all skin cancers1112. Lesions of SEC often present similarly to morpheaform basal cell carcinoma, with a solitary, firm nodule or plaque with fine telangiectasis on the head, neck and less commonly trunk, usually in the fourth to seventh decade of life413. The current case also exhibited a coin sized solitary pinkish nodule with fine telangiectasis. To the best of our knowledge, only 10 cases of SEC presented on the extremities, including our case, have been reported (Table 1)5678910. In this series of 10 cases, there were 7 women and 3 men, ranging age at diagnosis of SEC from 42 to 94 years with an average age of 56 years. Although onset age of 3 cases is not precisely informed, the onset age ranged from 14 to 68 years. Five lesions occurred on the hand and arm, five lesions on the leg and toe.

SEC often shows locally very destructive lesions with deep invasion and perineural invasion; local recurrences are common, but metastasis are rare3. Our case was also localized and didn't show any metastasis and recurrences.

Histologically, SEC have a variety of histological feature and show dilated tubules within dense fibrocollagenous matrix, sometimes with a tadpole appearance, small neoplastic ducts, solid islands, cellular cords, and keratinizing and nonkeratinizing cysts14. Cells show mild to marked nuclear atypia, usually of moderate atypia and a variable number of mitoses. SEC also presents with an infiltrative growth pattern with deep invasion and often extends into the subcutaneous tissue3. The differential diagnosis of SEC includes cutaneous adenoid cystic carcinoma, metastatic adenocarcinoma, sclerosing basal cell carcinoma, and syringoma15. SEC resembles syringoma by showing ductal, cystic and comma-like epithelial components. It differs from syringoma by its cellularity, anaplasia and deep invasiveness1. Immunohistochemical staining of SEC has been described as quite variable, although cytokeratins, EMA and CEA are routinely noted to be positive. In our case, the immunohistochemical analysis of CEA was slightly reactive, but the immunohistochemical analysis of CK7 and EMA were strongly reactive. Treatment of choice for localized lesions is the surgical excision with clear margin. Chemotherapy and radiation therapy should be considered as a treatment option for metastatic lesions. In our patients, the lesion was localized and didn't recur after treatment with surgical excision. In nine cases of SEC presented on extremities, 3 cases showed recurrence, 1 case distant metastasis. Therefore, it is thought that SEC of extremities also shows local recurrence and distant metastasis like SEC of other sites.

We have reported a case of SEC of the thigh presenting as a coin sized round shaped erythematous to pinkish ulcerative nodule with no metastasis for an 80-year history. Although SEC usually present on the head and neck, it also can be found on the extremity. To the best of our knowledge, only 9 cases were located on the extremities.