Eccrine porocarcinoma mimicking a venous leg ulcer.

Abstract

Eccrine porocarcinoma (EPC) is a rare, malignant skin tumour arising from the ductal portion of eccrine sweat glands and was first described by Pinkus and Mehregan in 1963 1. With a 20% rate of local recurrence and the potential to metastasize in regional lymph nodes in another 20% of cases 2, EPC often takes an aggressive clinical course 3. Organ spreading is only found occasionally, but with a very poor prognosis 4. EPC arises most commonly (40–50%) on the lower leg, but can also be found in other regions like trunk or neck where a clinical diagnosis can be difficult 5. Moreover, diagnosis can be complicated by the long clinical course which the tumour takes when slowly developing de novo or from a pre-existing, clinically harmless eccrine poroma which can be found by investigation in 20% of cases 6. An 82-year-old male was referred to our department for evaluation of a chronic leg ulcer which first appeared 2 years ago on the right lateral lower leg initially as a scaling plaque. During the 2 years prior to first admission to our clinic, the patient was treated regularly by his general practitioner. Detailed treatment regimen is not known. Two weeks ago, a varicose vein stripping had been performed in an external clinic (details not known). For the first time, a biopsy specimen from the ulcer was taken during this surgical intervention and revealed an eccrine porocarcinoma. Patient's medical history was clear and he had no current medication. On admission to our department, physical examination revealed an ulcer of the lateral right leg, which was 3 cm × 4 cm in size and had a peripheral erythematous margin. No lymphadenopathy in the inguinal or axillary areas was noted. Initial laboratory studies revealed a normal blood cell count, slightly increased C-reactive protein (5·1 mg/l; normal < 5·0 mg/l) and lactatdehydrogenase (290 U/l; normal < 200 U/l) levels. No clinical signs for an infection were found. Several biopsy specimens were obtained from the ulcerated area and from the livid non-ulcerated margin of the tumour to determine the extent of the lesion. The specimen from the central lesion showed asymmetrical infiltrative cords of basophilic tumour cells with cytologic atypia and atypical mitoses. Together with the focal ductal differentiation these results were concordant with the diagnosis of an eccrine porocarcinoma. A total excision of the ulcerated tumour with a clinical safety margin of 10 mm and down to the fascia was performed under local anaesthesia and the resulting defect of 5 cm in diameter was provided with a mesh graft skin transplant from the right upper leg 14 days after when sufficient granulation tissue had appeared. Microscopic examination approved the diagnosis of eccrine porocarcinoma with a vertical tumour thickness of 4 mm and showed clear surgical margins. Staging procedures (chest X-ray, abdominal sonography, lymph node sonography) excluded organ or lymph node involvement. The patient remains with no evidence of disease at 6-months follow-up. Malignant tumours mimicking a vascular leg ulcer are often diagnosed with delay when a response to appropriate treatment is lacking for several months or nodular expansion is observed. Other symptoms such as abnormal bleeding or unusual pain can confirm the suspicion of malignant origin of the ulcer. Prior injuries, burn scars or recurrent infections can additionally provide malignant transformation of preexisting vascular ulcers 7. EPC clinically presents as a slow-growing painless nodule or infiltrated plaque; squamous cell carcinoma, Merkel cell carcinoma and cutaneous lymphoma are included among the differential diagnoses. In the present case, a chronic ulceration was treated over a period of 2 years under the diagnosis of a venous leg ulcer and surgical intervention for chronic venous insufficiency was also performed. It was during phlebological surgery, when the idea of histological evaluation came up for the first time, the EPC could be diagnosed and has since been treated adequately, but with delay. Eccrine porocarcinoma are most common in elderly patients with a preference for females. The tumours which occur in most cases on the trunk, head, neck or lower extremities often show a longstanding history and develop quite slowly over years, some of them following a preexisting benign eccrine poroma 8. In our case, no former skin lesions were described. EPC shows a high potential for a lymphatic invasion and epidermotropic metastases can also be found 9. Factors such as vertical tumour depth, number of mitoses and vascular invasion are predictive of a poor prognosis 10. Histological confirmation about the correct clinical diagnosis is obtained by performing multiple biopsies on several points of the ulcer. The risk of false-negative results of single biopsies must be considered. Some authors recommend biopsy of all chronic wounds within 3 months when recalcitrant response is observed 11. The treatment of choice for a confirmed EPC is a wide local excision of the primary tumour 12. In cases of more infiltrative carcinoma, surgical resection should be performed with histological confirmation of the tumour-free margins by micrographic control of surgical margins, for example Mohs micrographic surgery 13. Histological analysis with special immunohistochemical staining is essential in establishing a conclusive diagnosis. Staging procedures to exclude lymph node or organ involvement are mandatory 14. Sentinel lymph node sampling is controversial but may be helpful for prognosis in cases of thick tumours or with high mitotic rates 15. Even lymphadenectomy in cases when lymphadenopathy is suspected can be recommended because lymph node involvement of EPC is found in 20% of cases. While initial surgical treatment is curative for most of the cases, no standard treatment protocols exist for metastatic EPC 6. Various chemotherapeutics such as docetaxel, cyclophosphamide and cisplatin have shown only insufficient response 16. An electrochemotherapeutical approach for local recurrency or cutaneous metastases has been described while radiation therapy is only of little benefit 2. As a conclusion, a high level of suspicion is important in early detection of malignant EPC in chronic leg wounds whenever ulcers fail to respond to conventional therapies. The high metastatic potential of EPC emphasizes the need for early detection and complete excision of this unusual tumour. Cornelia Erfurt-Berge, MD, Michael Erdmann, MD, Kathrin Brauner, MD, & Juergen Bauerschmitz, MD Department of Dermatology, University Hospital Erlangen, Erlangen, Germany Cornelia.Erfurt-0Berge@uk-erlangen.de