Six months of treatment with fixed-dose, alternate-day isotretinoin (20 mg) plus topical 1%clindamycin gel was found to be effective in the treatment of moderate acne in adult patients, with a low incidence of side-effects.

SIR, We are grateful to Dr Guerrini and colleagues for their interest in our study and we take this opportunity to clarify our opinions.We demonstrated the presence of high-risk mucosal human papillomavirus (HPV) genotypes from a considerable number of dysplastic naevi and primary melanomas using two different polymerase chain reaction (PCR)-enzyme-linked immunosorbent assay methods, concluding that the presence of the virus may be a cofactor in development and progression of these pathologies. 1 We agree with other colleagues that our results need further evaluation. In particular, PCR is a highly sensitive technique, able to detect the presence of total DNA from tissue samples at a level of about one genome per cell. 2-4 All previous studies aimed to detect HPV DNA in skin cancer using PCR procedures were in most cases unable to conclude that the DNA detected was entirely derived from cancer cells. In fact, PCR procedures are not suitable to ascertain if the HPV DNA detected is derived exclusively from cancer cells, but rather if its presence is due to a tumour surface contamination. 5 On the other hand, different methods, including immunohistochemistry (IHC) and in situ hybridization (ISH), have been demonstrated as more specific, but less sensitive than PCR methods.On the basis of these considerations, we are submitting for publication a second part of our studies, concerning the evaluation of the presence of mucosal high-risk HPV in primary melanoma and its colocalization with a tumoral melanocytic marker in the same section, using a very sensitive method that combines an enzyme-amplified fluorescent ISH with a chemiluminescent IHC method for the detection of the tumoral melanocytic marker HMB-45. The antimelanoma monoclonal antibody HMB-45 used in the chemiluminescent IHC is widely used in diagnostic pathology owing to its great specificity and sensitivity in identifying pigmented tumours such as malignant melanoma, while normal melanocytes are unreactive. 6 M. LA P L A C A

431 2 Haig DM, Huntley JF, MacKellar A et al. Effects of stem cell factor (kit-ligand) and interleukin-3 on the growth and serine proteinase expression of rat bone-marrow-derived or serosal mast cells. Blood 1994; 83: 72-83. 3 Samoszkut MK, Kanakubo E, Chan JK. Degranulating mast cell in fibrotic regions of human tumors and evidence that mast cell heparin interferes with the growth of tumor cells through a mechanism involving fibroblasts. BMC Cancer 2005; 5: 121. 4 Meininger CJ, Yano H, Rottapel R, Bernstein A, Zsebo KM, Zetter BR. The c-kit receptor ligand functions as a mast cell chemoattractant. Blood 1992; 79: 958-963. 5 Mekori YA, Oh CK, Metcalfe DD. IL-3-dependent murine mast cells undergo apoptosis on removal of IL-3. Prevention of apoptosis by c-kit ligand. J Immunol 1993; 151: 3775-3784. 6 Frenz AM, Gibbs BF, Pearce FL. The effect of recombinant stem cell factor on human skin and lung mast cells and basophil leukocytes. Inflamm Res 1997; 46: 35-39. 7 Hart PH, Grimbaldeston MA, Finlay-Jones JJ. Sunlight, immunosuppression and skin cancer: role of histamine and mast cells.

The results of our study highlighted an alarming increase in the percentage of PPNG and QRNG strains over the years. Emergence of N. gonorrhoeae isolates with decreased susceptibility to third-generation cephalosporins is a cause of concern and thus emphasises the importance of antimicrobial susceptibility testing.

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