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Open Access Highly Accessed Case report

Malignant melanoma arising from a perianal fistula and harbouring a BRAF gene mutation: a case report

Conrado Martinez-Cadenas1*, Nuria Bosch2, Lucas Peñas2, Esther Flores-Couce1, Enrique Ochoa1, Javier Munárriz3, Juan P Aracil4, Marcos Tajahuerce5, Ramón Royo2, Rafael Lozoya6 and Enrique Boldó6

Author Affiliations

1 Molecular Biopathology Lab, Castellon Province Hospital, Ave. Doctor Clara 19, Castellon, 12002, Spain

2 Pathology Service, Castellon Province Hospital, Ave. Doctor Clara 19, Castellon, 12002, Spain

3 Oncology Service, Castellon Province Hospital, Ave. Doctor Clara 19, Castellon, 12002, Spain

4 Plastic Surgery Service, Castellon Province Hospital, Ave. Doctor Clara 19, Castellon, 12002, Spain

5 Nuclear Medicine Service, Castellon Province Hospital, Ave. Doctor Clara 19, Castellon, 12002, Spain

6 Surgical Oncology Unit, Castellon Province Hospital, Ave. Doctor Clara 19, Castellon, 12002, Spain

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BMC Cancer 2011, 11:343  doi:10.1186/1471-2407-11-343

Published: 9 August 2011

Abstract

Background

Melanoma of the anal region is a very uncommon disease, accounting for only 0.2-0.3% of all melanoma cases. Mutations of the BRAF gene are usually absent in melanomas occurring in this region as well as in other sun-protected regions. The development of a tumour in a longstanding perianal fistula is also extremely rare. More frequent is the case of a tumour presenting as a fistula, that is, the fistula being a consequence of the cancerous process, although we have found only two cases of fistula-generating melanomas reported in the literature.

Case Presentation

Here we report the case of a 38-year-old male who presented with a perianal fistula of four years of evolution. Histopathological examination of the fistulous tract confirmed the presence of malignant melanoma. Due to the small size and the central location of the melanoma inside the fistulous tract, we believe the melanoma reported here developed in the epithelium of the fistula once the latter was already formed. Resected sentinel lymph nodes were negative and the patient, after going through a wide local excision, remains disease-free nine years after diagnosis. DNA obtained from melanoma tissue was analysed by automated direct sequencing and the V600E (T1799A) mutation was detected in exon 15 of the BRAF gene.

Conclusion

Since fistulae experience persistent inflammation, the fact that this melanoma harbours a BRAF mutation strengthens the view that oxidative stress caused by inflammatory processes plays an important role in the genesis of BRAF gene mutations.