Gastrointestinal Stromal Tumor of Appendix: A Rare Case
Background: Gastrointestinal stromal tumors (GIST) are rare. They arise from mesenchymal tissue and are extremely rare in the vermiform appendix. Few cases have been found in this location. Objective: To understand the histogenesis, biologic behaviour and histologic patterns. Method: A resected specimen of appendicular mass was received in a container with 10% formalin fixative. This was processed in histokinette, embedded in paraffin, and blocks were made. Thin serial sections were taken of 4-5 microns and stained with haematoxylin and eosin. Result: Histologically, mucosa showed mononuclear cells, the submucosa had few congested vessels and loose connective tissue. The muscular layer was increased showing fascicles or bundles of smooth muscle cells, majority of them having epithelioid type of nucleus with moderate pink cytoplasm and was diagnosed as a GIST (epithelioid type) of appendix. Conclusion: Mesenchymal tumors of the appendix are extremely rare. It is important to recognize and correctly diagnose gastrointestinal tumor for effective and justified therapy.
Gastrointestinal Stromal Tumor (GIST) has evolved as a separate entity among the gastrointestinal mesenchymal neoplasm with a specific histogenesis and is defined as a spindle or epithelioid cell lesion arising in the wall of the gastrointestinal tract. GIST of appendix is extremely rare with only a few cases that are available in the literature to date. Miettinen and Sobin described four cases of GIST in appendix. Mostly, gastrointestinal stromal tumors occur in the stomach (60-70%), followed by small intestine (25-35%), with a rare occurrence in the colon and rectum (3%), esophagus (2%), and appendix.
In the literature it is said that gastrointestinal tumor has a peak incidence in the late sixth and early seventh decades of life with a male preponderance. Herewith, we report an extremely rare and unique case of appendiceal GIST with available literature and its biologic behavior.
A 42-year-old male presented with pain in the abdomen and a swelling in right iliac fossa, for one week. Clinical diagnosis and investigations pointed to a pathology in the appendix. The patient was taken for surgery. The appendicular mass was resected and sent for histopathologic examination.
Gross: The specimen of appendix measured 5 x 4 x 3 centimetres (cm) in size and showed nodularity (Figure 1). On cut section, the lumen of the appendix was obliterated with thickening of the wall, and areas of greyish white lobularity was seen (Figure 2).
Microscopic: Sections from the appendix showed the mucosal layer made up of columnar and goblet cells with mononuclear cell infiltrates. The submucosal area showed loose stroma along with blood vessels, some showing
congestion. The muscular layer was increased in thickness, showing bundles or fascicles of spindle smooth muscle cells, having an elongated nucleus. Majority of the spindle cells are plump, vesicular type resembling epithelioid cells along with a moderate amount of pink cytoplasm (Figure 3). This was diagnosed as a GIST of appendix, epithelioid cell type.
Gastrointestinal stromal tumor is the most common mesenchymal tumor in the gastrointestinal tract, however GIST of appendix is extremely rare, with just a few available cases in literature to date.
The most common peak incidence of this tumor as per available literature was in late sixth and early seventh decades of life with male preponderance. In our case, the age of occurrence was in a much younger male of 42 years age, showing a relatively early onset as compared to the reported peak ages in the literature. It has been noted that the most frequent site is the stomach (52%), followed by the small intestine (25%), large bowel (11%) and oesophagus (5%).
Gastrointestinal stromal tumor has evolved as a separate entity among gastrointestinal mesenchymal neoplasm. It represents a morphologically heterogenous group of tumors, which were once thought to be a poorly defined pathologic oddity; it has emerged in recent years as a distinct entity with a specific histogenesis.
It used to be a collective term referring to primary mesenchymal tumor of gastrointestinal tract. It is now considered to be a tumour that originates from the intestinal cells of Cajal or its precursor in the gastrointestinal tract and has the expression of the tyrosine kinase receptor KIT in most cases.
Gastrointestinal stromal tumor of appendix is extremely rare in this location. Gastrointestinal stromal tumor needs to be recognized as a separate entity for effective and justified use of therapy. It is important to recognize and correctly diagnose, rather than lumping all gastrointestinal mesenchymal tumors under the heading of GIST. This entity should also be considered in the differential diagnosis of an appendiceal mass apart from carcinoid or adenoma. Hence, careful histopathological examination of the sections is most warranted.
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