Case reportA 71-year-old Caucasian woman presented with a 4-year history of an asymptomatic nodule within the left labia majus. A firm, irregular, 3 cm dermal lesion was noted, with an overlying area of macular hyperpigmentation. The nodule was non-tender and there were no other similar lesions at other body sites. A clinical diagnosis of an epidermoid cyst was made and excision biopsy undertaken. Histology revealed a dermal tumour consisting of large cells with a granular eosinophilic cytoplasm and small, bland, round or oval nuclei. Marked overlying pseudoepitheliomatous hyperplasia was noted. No cytological atypia or mitoses were seen in the dermal infiltrate. Immunohistochemistry showed the cytoplasmic granules to be S100 and D-PAS positive, and nuclear S100 positivity was also noted (Figure 1). Small groups of tumour cells were noted to infiltrate deeply into the dermis, and the tumour was reported to be incompletely excised.

The histopathology and clinical presentation of 19 cases of primary gastrointestinal lymphoma is described. Our patients are similar to others in the Middle East but have a lower incidence of diarrhoea and malabsorption. All revealed a widespread chronic inflammatory background. Four patients with primary gastric lymphoma had endoscopic biopsies from the duodenum; these biopsies were completely free from tumour but showed a moderate to severe diffuse lymphoplasmacytic infiltrate. Electron microscopy shows that tumour cells penetrate basement membranes and invade the epithelium which becomes thin and attenuated. Substances which inhibit lymphocyte tropism might be useful in preventing intestinal ulceration. The MALT concept has been found useful in classification of the tumours. Two patients with unusual mesenteric node histology are described and it is thought that the appearances may indicate a substantial capacity for differentiation in the group of tumours.