Spirochaetes have been found in the alimentary tract and faeces of apparently healthy people.' In some animals similar infestation may cause an acute and often fatal diarrhoeal illness.2 A review of 100 consecutive rectal biopsy specimens obtained from patients with rectal bleeding or diarrhoea showed that 10 had spirochaetosis.3 In two of these patients no other underlying cause for the symptoms could be found and it was not clear whether these organisms were just commensals. The authors suggested that antibiotic treatment in such cases may provide an answer to this problem. We describe two patients with spirochaetosis who presented with diarrhoea and rectal bleeding. Both improved after treatment with metronidazole. Case reports CASE 1A 54-year-old man presented in October 1979. Since 1974 he had experienced self-limiting episodes of watery diarrhoea and rectal bleeding associated with the sigmoidoscopic and histological changes of active non-specific granular proctitis. He presented with a further episode of rectal discomfort and loose slimy diarrhoea of three weeks' duration. Physical examination was unremarkable, and stool culture and microscopy were negative. A double-contrast barium enema was normal. Sigmoidoscopy confirmed active proctitis with considerable rectal tenderness. A repeat rectal biopsy specimen showed chronic inflammatory changes. A haematoxyphilic fuzzy border typical of intestinal spirochaetosis was seen on the surface epithelium (figure). After metronidazole 1 g by suppository twice daily for five days his diarrhoea stopped and rectal discomfort diminished. Sigmoidoscopy two months later confirmed improvement in the proctitis. Histology again showed chronic inflammation but the fuzzy border had disappeared.During March 1980 his diarrhoea and rectal bleeding recurred. A further rectal biopsy specimen again showed a fuzzy brush border. Electron microscopy showed spiral organisms 3 /m in length and 0-2 jum diameter between the microvilli of the rectal epithelium. Transverse section on electron microscopy showed axial filaments with a rosette formation. He received a further seven-day course of metronidazole suppositories after which his symptoms disappeared. A repeat rectal biopsy specimen showed that the spirochaetal infestation had disappeared. CASE 2A 49-year-old man presented in September 1980 with a history of two weeks' watery diarrhoea that had started while he was on holiday abroad and one week's tenesmus and fresh rectal bleeding. Physical examination was satisfactory and stool culture and microscopy were negative. A doublecontrast barium enema was normal. On sigmoidoscopy the rectal mucosa appeared normal. A rectal biopsy specimen showed normal histology apart from a fuzzy blue brush border over the surface epithelium (figure). Electron microscopy showed spirochaetes identical with those in case 1. Metronidazole 400 mg four times a day by mouth for 10 days abolished his symptoms. A further biopsy specimen in December showed that the spirochaetes had disappeared. Comment

One hundred and twenty-nine cases of malignant melanoma seen at Bangour General Hospital over an eleven year period were reviewed clinically and histologically. In 51 patients (39.5%) there was a history of pre-existing pigmented lesion at the site of the melanoma. In 14 cases (10.8%) histology confirmed traces of a benign melanocytic naevus. The relationships between naevus cells and malignant melanocytes are described. The patterns most frequently observed were those of intradermal naevus cells in the deeper part of an invasive melanoma and of a compound naevus undergoing malignant change in its junctional component. From these histological observations a histogenetic sequence of events is postulated. In the 37 patients with a positive history of a preceding pigmented lesion but no histological traces of a naevus, the percentage incidence of Lentigo Maligna (LM) and Superficial Spreading Melanoma (SSM), as compared with the 78 patients with a negative clinical history, was significantly higher than the incidence of nodular melanoma (NM). Although LM and SSM are thought to have separate histogenesis and aetiology, they share an important clinical and histological factor, i.e. in both, the radial growth phase is preceded by a, more or less, prolonged stage of intraepidermal horizontal growth. It is postulated that this pre-existing lesion of atypical melanocytic proliferation rather than a hypothetical benign naevus is in most cases the precursor of an invasive melanoma.

Summary Two patients are described who had used intrauterine contraceptive devices and developed pelvic actinomycosis with ureteric obstruction.

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Patients attending a breast clinic in two different periods were studied. In the first period fine needle aspiration cytology (FNAC) was not available and in the second it was used on all discrete solid breast lumps and reported immediately in the clinic. With the use of FNAC the overall surgical excision rate for discrete solid lumps was reduced from 83 per cent to 41 per cent and the excision rate in patients with benign disease was reduced from 74 per cent to 23 per cent (P less than 0.001). All patients with breast cancer in the second period had malignant cytology and no patient with benign or acellular cytology has been shown, after a minimum follow-up period of 18 months, to have breast cancer. Using FNAC with immediate reporting, the number of operations performed in patients with benign breast disease can be safely reduced.

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Local excision of rectal tumours SirWe read with interest your recent article by C . W. Mann (Br J Surg 1985; 72(Suppl.): S57-8), in which the importance of patient selection is stressed. It is stated that only tumours of favourable cytological differentiation ('well' or 'average' histological grade) are suitable for these local radical techniques.It is important to draw attention to the fact that it is not possible to exclude accurately all poorly differentiated tumours pre-operatively based on the results of rectal biopsies. In a recent study' we found that 70 per cent of poorly differentiated growths had been thought to be of only average grade when the rectal biopsy was examined. These findings were confirmed by Elliott et a/.' who found that only 17 of 42 poorly differentiated tumours were correctly identified as being of unfavourable histological grade on rectal biopsy, a 60 per cent error.The discovery of unfavourable histology after local excision may result in a medically unfit patient being subjected to further surgery. lnaccuracy in the histological grading of rectal biopsies means that it cannot be certain that selection is completely correct when advocating local excision.