Knf

Fig. 3.46 Benign stromal tumours. A Vague palisading pattern reminiscent of a nerve sheath tumour. B Spindle cells with prominent cytoplasmic vacuo-lation. C An epithelioid pattern corresponding to the previous designation of leiomyoblastoma.

Fig. 3.46 Benign stromal tumours. A Vague palisading pattern reminiscent of a nerve sheath tumour. B Spindle cells with prominent cytoplasmic vacuo-lation. C An epithelioid pattern corresponding to the previous designation of leiomyoblastoma.

Fig. 3.45 Gastrointestinal stromal tumour. A Ulceration is present at the summit of the lesion. B Cut surface showing transmural extension.

Fig. 3.45 Gastrointestinal stromal tumour. A Ulceration is present at the summit of the lesion. B Cut surface showing transmural extension.

Fig. 3.47 Examples of mutations of the exon 11 of the c-kitgene in gastrointestinal stromal tumours. A Nucleotide sequence of the c-kitgene. B Predicted amino acid sequences of the mutant KIT. The top line in each figure represents the germline I and the wild type KIT protein, respectively. Each line below them re-presents one case. The codons are indicated by numbers. The shaded areas correspond to deletions (black) or point mutations (gray). Courtesy of Dr. J. Lasota, Washington D.C.

Fig. 3.47 Examples of mutations of the exon 11 of the c-kitgene in gastrointestinal stromal tumours. A Nucleotide sequence of the c-kitgene. B Predicted amino acid sequences of the mutant KIT. The top line in each figure represents the germline I and the wild type KIT protein, respectively. Each line below them re-presents one case. The codons are indicated by numbers. The shaded areas correspond to deletions (black) or point mutations (gray). Courtesy of Dr. J. Lasota, Washington D.C.

phorylation) of the tyrosine kinase and further the phosphorylation cascade that leads into mitogenic activation {928, 713, 1310, 1356}. The most common mutations appear to be in-frame deletions of 3-21 base pairs, followed by point mutations and occasionally described insertions {475, 713, 1018, 1289}. Association of neurofibromatosis type I has been described in rare cases; these tumours represent phenotypical GISTs, but molecular genetic studies are not available {1681A}. The rare combination of pulmonary chondroma, gastric epithe-lioid GIST and paraganglioma in the Carney triad has probably a common yet unknown genetic link {246}.

Prognosis and predictive factors

The prognosis of GISTs is largely dependent on the mitotic rate, size, depth of invasion, and presence or absence of metastasis {462}. Although race and gender did not play a role in survival rates in the SEER data for gastric carcinomas, the 5-year survival rates for sarcomas varied considerably, e.g. 49% 5-year survival for males versus 74% for females; 37% for Blacks versus 66% for Whites {1928}.

Other mesenchymal tumours

Gastrointestinal autonomic nerve tumour (GANT)

Gastrointestinal autonomic nerve tumour (GANT), or the previous designation plex-osarcoma, has been applied to mesenchymal tumours that have shown ultrastructural features of autonomic neurons:

Fig. 3.48 Malignant gastrointestinal stromal tumours. A Tumour cells form perivascular collars surrounded by necrosis. B Numerous mitotic figures are present. 64 Tumours of the stomach
Fig. 3.49 Glomus tumour. Uniform tumour cells and dilated thin-walled blood vessels.

Fig. 3.50 Gastric schwannoma including part of the lymphoid cuff.

Fig. 3.51 Gastric lipoma.

cell processes with neurosecretory type dense core granules and arrays of micro-tubules {702, 701, 1023, 2038}. Histologi-cally, such tumours have shown a variety of spindle cell and epithelioid patterns similar to those seen in GISTs; at least some of these tumours are positive for KIT. It therefore appears that GANT and GIST groups overlap, and may even merge. Because electron microscopy is currently applied less widely for tumour diagnosis than before, GAN-type differentiation in gastrointestinal tumours is probably underestimated. Correlative light microscopic, ultrastructural, immuno-histochemical and molecular genetic studies are needed to resolve the question of the relationship of GANT and GIST.

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