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Notes: We describe the clinicopathological features of gastrointestinal autonomic nerve tumours in nine patients where the diagnosis was confirmed by electronmicroscopy. Most patients presented with abdominal pain. At laparotomy, large intra-abdominal tumour masses were found which tended to be cystic and haemorrhagic. The predominant histological patterns were nests, sheets and fascicles of spindle and epithelioid cells. Immunohistochemistry showed positive staining for neuron specific enolase (9/9), PGP 9.5 (9/9), NKI/C3 (7/9), vimentin (7/9), α-smooth muscle actin (5/9), vasoactive intestinal peptide (3/9) and CD34/QBend10 (2/9). Grimelius staining was positive in two of nine cases. All tumours were negative for CAM 5.2, chromogranin, synaptophysin, Leu 7, neurofilament protein, muscle-specific actin (HHF-35) and desmin (D33). Ultrastructural examination showed cellular processes and dense-core granules in all cases. Three tumours had microtubules and/or intermediate filaments, particularly in cell processes. Skeinoid fibres were seen in three cases. No convincing synapses or small (synaptic-type) vesicles were identified. There was no evidence of epithelial, smooth muscle or nerve sheath differentiation. Two patients died due to tumour, two died of unknown causes and the remainder are alive 2–44 months after presentation. Four of the five survivors have recurrent/residual intra-abdominal tumour. So-called gastrointestinal autonomic nerve tumours are apparently slow-growing malignant tumours showing neuronal differentiation. Four cases arose in the mesentery/retroperitoneum or omentum rather than bowel wall and therefore a more appropriate nomenclature might be intra-abdominal stromal tumour with neuronal differentiation.

Notes: Aims: We describe the cutaneous pseudoneoplastic lesions in two patients with nodular erythema elevatum diutinum, a rare chronic disorder in which polymorph nuclear fragmentation (leukocytoclasis) is present within dermal nodules showing spindle cells and fibrosis. In both cases diagnostic difficulty was encountered clinically and pathologically and various benign and malignant neoplasms were considered in the differential diagnosis. Methods and results: Immunohistochemically the spindle cells were negative for CAM5.2, AE1/3, S100 protein and desmin (D33). They were positive for vimentin and focally positive for CD34 and α-smooth muscle actin. Some of the spindle cells were positive for Mac 387 and KP1(CD68). By electron microscopy, the lesions were shown to consist of fibroblasts/myofibroblasts and fusiform macrophages. Conclusions: Increased awareness of the features described will help to avoid misdiagnosis as a neoplastic process.

Notes: The histological, immunohistochemical and electron microscopic features of a primary adenomyoepithelioma of skin, a rare sweat gland tumour, are reported.〈section xml:id="abs1-2"〉〈title type="main"〉Methods and results:The tumour occurred on the back of a 92-year-old woman. It was composed of well-formed tubules lined by epithelial cells surrounded by clear or spindled myoepithelial cells. Immunohistochemically, the epithelial cells exhibited strong cytokeratin (CAM5.2) and weak carcinoembryonic antigen positivity. The myoepithelial cells showed diffuse positivity for smooth muscle actin and focal positivity for S100 protein. Ultrastructurally, the myoepithelial cells contained myofilaments with focal densities and hemi-desmosomes. They were limited by well-formed basal lamina. The tumour was associated with a small eccrine spiradenoma.〈section xml:id="abs1-3"〉〈title type="main"〉Conclusion:We predict that the tumour will behave in a benign fashion. There is no evidence of recurrence or metastasis 28 months later.

Notes: To study the clinical and pathological features of primary malignant peripheral primitive neuroectodermal tumours (PNETs) of the skin and subcutaneous tissue, to discuss the differential diagnosis, and to review the existing literature on these tumours.〈section xml:id="abs1-2"〉〈title type="main"〉Methods and results:Eight cases of PNETs presenting in the skin and subcutaneous tissue were identified from the pathology records of the Christie Hospital, Manchester. Detailed immunohistochemical studies were performed on all cases and seven tumours were subjected to electron microscopic examination. Detailed clinical and follow-up information was obtained on seven cases. Six tumours occurred in children and adolescents and two were seen in young adults (age range, 8–36 years). No sex or site predilection was observed. Five tumours occupied the dermis and subcutis and three were entirely located in the subcutaneous tissue. Microscopically, they were composed of small round cells and seven tumours contained glycogen. Only one tumour focally exhibited Homer–Wright rosettes and neuropil. Two tumours contained rhabdoid or plasmacytoid cells in places and all cases showed microcystic and pseudovascular spaces. Immunostains revealed MIC2 (8/8), NSE (7/8), PGP9.5 (7/8), β2 microglobulin (7/8), neurofilament protein (6/8), S100 protein (3/8), synaptophysin (2/8) and Leu-7 (1/8) positivity. Anomalous cytokeratin (4/8), desmin (2/8), myoglobin (2/8), NKIC3 (4/8) and GFAP (1/8) staining was also noted. Ultrastructurally, neuroendocrine granules were detected in five cases and one case exhibited microtubules in processes. Adequate follow-up information was available in four cases. One patient died of metastatic disease. One child developed axillary lymph node metastasis but is alive with no evidence of disease 96 months after treatment. Two other patients are alive with no residual or recurrent disease 44 and 52 months after excision and radio/chemotherapy.〈section xml:id="abs1-3"〉〈title type="main"〉Conclusion:PNETs are rare malignant small round cell tumours of the skin and subcutaneous tissue which are probably underdiagnosed. A correct diagnosis can be made on light microscopic features, demonstration of neuroendocrine granules on electron microscopy and a combination of MIC2, β2 microglobulin, and more than one neural marker positivity. These neoplasms should be differentiated from other cutaneous neoplasms composed of small round cells. The number of cases of cutaneous PNETs studied so far is rather small, and no firm conclusion can be drawn about their behaviour but long-term survival is possible in some cases.

Notes: VS38 was originally described as a marker of neoplastic and non-neoplastic plasma cells. We recently described its immunoreactivity with melanocytic lesions. The aim of the present study was to investigate the reactivity of VS38 with various neuroendocrine tumours. Using paraffin sections of routinely processed archival tissue we found that 72% of 50 neuroendocrine tumours tested showed immunohistochemical positivity for VS38. A wide spectrum of neuroendocrine tumours were positive. Use of a panel of markers and awareness of the lack of specificity of VS38 will avoid misdiagnosis, particularly when neuroendocrine tumours and other lesions which react immunohistochemically with this antibody are located at unusual sites and exhibit plasmacytoid features.