MCL usually involves the gastrointestinal tract as either single, isolated or multiple polyps as so-called multiple lymphomatous polyposis [11
]. These polyps are usually found throughout the gastrointestinal system but frequently there is a larger polyp in ileocecal valve region accompanied by mesenteric lymph node involvement. Appendiceal involvement is by contiguity from ileocecal disease [15
]. With regards to the spindle and epithelioid cell tumor of the appendix, GIST is the first diagnosis to be considered since they are the commonest primary mesenchymal tumor of the gastrointestinal system. Appendiceal GIST is extremely uncommon, and to the best of our knowledge, only 7 cases have been reported thus far [16
]. These cases were all c-kit immunopositive; however c-kit
mutations were studied only in two cases [17
]. All reported cases are c-kit and CD34 positive but uniformly negative for S100, desmin, smooth muscle actin [16
]. The case described in this report showed a GIST pattern of immunohistochemistry with neuronal differentiation seen ultrastructurally.
In studies of GANT, 100% positivity for c-kit was noted, vimentin 92%, neuron specific enolase 90%, CD34 58%, S100 39% to 44%, synaptophysin 31%, chromogranin A 11%, neurofilament 16%, α smooth muscle actin 10%, vasoactive intestinal peptide 20% [8
]. Cytokeratin, desmin and HHF35 are usually negative. Thus, the case described in this report fulfills the morphological and immunophenotypic features of a GIST showing neuronal differentiation. The absence of a c-kit
mutation does not exclude this diagnosis as only 50% of such GISTs demonstrate a molecular aberration in the c-kit
Amongst the several spindle cell lesions that are considered in the light microscopic differential diagnosis, a schwannoma is an important consideration in view of the S-100 positivity. It is a rare entity in the gastrointestinal tract, mainly involves the stomach but has also been reported in the colon, esophagus and rectum [19
]. Although our case was GFAP and S100 positive, it was also c-kit positive and schwannomas are negative for c-kit. Also the common histological features of gastrointestinal schwannomas such as a lymphoid cuff with the germinal centers, mainly spindle cell component with indistinct cytoplasm and wavy nuclei trapped between linear collagen were absent in our case [19
]. Furthermore, absence of ultrastructural features of schwannoma such as basal membrane which tapered in both side and the tumor did not exhibit lymphocytic infiltration.
Synchronous presentation of GIST with another tumor has been reported and coexistence with hematological disorders has also been documented [22
]. These hematological disorders include: chronic lymphocytic leukemia, mucosa-associated lymphoid tissue lymphoma (MALT-lymphoma), non-Hodgkin lymphoma, Burkitt lymphoma, anaplastic large cell lymphoma, high grade follicle center lymphoma (follicular lymphoma) and plasmacytoma [25
]. However, synchronous presence of mantle cell lymphoma with either GIST or GANT has not been reported previously. GANT on the other hand, has been reported synchronously with adrenal ganglioneuroma, neurofibromatosis and Carney's triad. In this report, we described two unusual coexistent lesions of the appendix: a GIST showing autonomic nerve differentiation (GANT) in a background of mantle cell lymphoma.