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Figure 20.18 contd... Gastric carcinoma, gross appearance of subtypes and their corresponding dominant histological patterns. CHAPTER 20

Other Carcinomas Carcinoid Tumour
Besides the various morphologic patterns of adenocarcinoma Carcinoid tumours are rare in the stomach and are usually
just described, other carcinomas that occur rarely in the non-argentaffin type but argentaffinomas also occur. Their
stomach are: adenosquamous carcinoma, squamous cell behaviour is usually malignant; they are described on
carcinoma and undifferentiated carcinoma, all of which are page 579.
morphologically similar to such tumours elsewhere.
Lymphomas of Gut
Leiomyosarcoma Primary gastrointestinal lymphomas are defined as
lymphomas arising in the gut without any evidence of The Gastrointestinal Tract
Leiomyosarcoma, though rare, is the commonest soft tissue systemic involvement at the time of presentation.
sarcoma, the stomach being the more common site in the Secondary gastrointestinal lymphomas, on the other hand,
gastrointestinal tract. appear in the gut after dissemination from other primary
site.
Grossly, the tumour may be of variable size but is usually
quite large, pedunculated and lobulated mass into the Gastric lymphomas constitute over 50% of all bowel
lumen. lymphomas; other sites being small and large bowel in
Microscopically, leiomyosarcoma is characterised by high decreasing order of frequency. Prognosis of primary gastric
cellularity and presence of mitotic figures. Tumour is lymphoma is better than for intestinal lymphomas. Primary
usually well-differentiated. lymphoma of stomach is the most common malignant gastric
tumour (4%) next to carcinoma.
Clinical manifestations of gastric lymphomas may be
Leiomyoblastoma (Epithelioid Leiomyoma) similar to gastric carcinoma. Age incidence for lymphomas
of the gastrointestinal tract is usually lower than that for
This is a rare tumour, the behaviour of which is intermediate
between clearly benign and malignant tumour. carcinoma (30-40 years as compared to 40-60 years in gastric
carcinoma) and may occur even in childhood. Relationship
with long-standing chronic H. pylori gastritis with lymphoid
Grossly, the tumour is large, circumscribed and projects
into the lumen. hyperplasia has been strongly suggested.
Microscopically, it is characterised by round to polygonal Grossly, gastric lymphomas have 2 types of appearances:
cells with clear perinuclear halos. The number of mitoses 1. Diffusely infiltrating type, producing thickening of the
determines the biological behaviour of the tumour. affected gut wall, obliteration of mucosal folds and