Gastric
stromal tumours
Previously named leiornyoma and leiomyosarcoma, the rather bland name of
stromal tumour is now used because the biological behaviour of these tumours is
unpredictable. Although it is reasonably straightforward for a pathologist to
say that one particular lesions has a benign appearance and, at the other
extreme, a tumour is highly malignant, there is a large number of tumours in
which the distinction between benign and malignant is unclear. In general terms
the larger the tumour and the greater mitotic activity the more likely it is to
metastasise. Within the gastrointestinal tract the stomach is the commonest site
for such turnouts.
The
incidence of the condition is unclear as small stromal tumours of the stomach
are probably quite common and remain unnoticed. Clinically obvious tumours are
considerably less common than gastric cancer. The aetiology is unknown.
The
only way that many stromal tumours are recognised is either that the mucosa
overlying the tumour ulcerates (Fig. 51.26) leading to bleeding or that they
are noticed incidentally at endoscopy. Because the mucosa overlying the tumour
is normal, endoscopic biopsy can be uninformative unless the tumour has
ulcerated. The appearance on barium meal is usually typical. Larger tumours
present with nonspecific gastric symptoms and in many instances may initially be
thought to be gastric cancer.
As
the biological behaviour is difficult to predict the best guide is to consider
the size of the tumour. Smaller tumours can be treated by wedge excision but
larger ones require a gastrectorny. By their nature these tumours spread via
the blood, and lymphatic metastases are relatively uncommon.
Common sites of spread include the liver, lungs and bone. Surgery is the
only treatment modality that can cure the disease; adjuvant chemotherapy has not
been shown to be beneficial. These tumours sometimes respond to systemic
chemotherapy, but this is palliative.