Case Report
A previous healthy 50 years-old female arrived at the emergency
department due to severe diffuse abdominal pain, and bloody diarrhea.
The patient had been suffering from similar, mild symptoms for about
three months and did not seek previous medical assistance before, for
fear of being infected with COVID-19. Physical examination was
unremarkable except for a slight, diffuse pain during abdominal
palpation, without tenderness. She had a surgical history of cesarean
section and surgical sterilization, and there was not prior family
medical history of congenital diseases. An abdominal CT scan revealed a
circumferential thickening on the descending colon with trans-mural
involvement, and an increased density of the peripheral fat, with a
probable neoplastic origin (Figure 1.), associated with mesenteric
adenopathy. The characteristics of the remaining abdominal organs were
unremarkable. Upper endoscopy showed a follicular gastritis, positive
for Helicobacter pylori in the histopathological analysis,
associated with a chronic inflammatory infiltrate with lymphoid
follicles formation - most of them with germinal centers - and moderate
acute infiltrate. Colonoscopy demonstrated a 4 cm sessile mass located
in the descending colon, 40 cm from the anal verge, covered with fibrin
and necrotic tissue (Figure 2a.). The lesion occupied around 80% of the
lumen, and multiple biopsies were obtained. The histopathological
analysis of the biopsies reported necrotic tissue, fibrin and cellular
debris without neoplastic features. The patient underwent laparoscopic
left hemicolectomy. A 15 cm long colon segment arrived at the pathology
laboratory, upon the mucosal surface of which a 4cm sessile polypoid
mass, cover in fibrin was identified (Figure 2b.). The lesion was
mucosal-submucosal based, the center of the lesion was yellow with
hemorrhagic foci, without thickening of the colonic wall. Multiple lymph
nodes were extracted from the mesenteric fat.
In the histopathological analysis, the polypoid mass was ulcerated at
the surface with a cap of granulation tissue, fibrin, cellular debris
and acute inflammatory infiltrate. The center of the lesion was composed
of well-circumscribed spindle cell proliferation. The spindle tumor
cells had tapered nucleus, uniform chromatin with a single nucleolus,
and a fascicular and sheet-like growth pattern. There were moderate
pleomorphisms, less than 5 mitotic figures in 50 high power fields, and
no variable cellular Antoni A and Antoni B areas or Verocay bodies. The
stroma of the tumor was collagenous, hypocellular, with lymphocytic
inflammatory infiltrate and small arterial vessels with hyalinized
walls. The immunohistochemical profile (Figure 3.) shows diffuse nuclear
and cytoplasmatic S100 expression, and positivity for SOX10 and GFAP
(Glial Fibrillary Acid Protein). The tumor cells were negative for KIT,
DOG1, SMA, Desmin, Caldesmon, HMB45, Melan-A, ALK-1, CD34, CD31, EMA,
Chromogranin, Synaptophysin, CD56, TLE-1, EMA and Cytokeratins. With the
morphological and the immunohistochemical profile, the colonic polypoid
mass was diagnosed as a Schwannoma.