A 57-year-old man with no stated past medical history presented to the
ED with complaints of headache and blurry vision that were getting
progressively more severe. These symptoms began about 6 months before
presentation. He also noted worsening bloody bowel movements.
A CT scan of the brain without contrast was performed on admission. It
revealed an enhancing right parietal lobe lesion. A chest/abdomen/pelvis CT
with IV contrast was subsequently performed that showed multiple large lymph
node masses in the mediastinum and right hilum, as well as a mass in the right
upper lobe. Two lesions were noted in the liver, as well as possible
rectosigmoid malignancy with possible extension into the perirectal space and
the rectosigmoid colon.
Further imaging was performed with contrast enhanced MRI to characterize
the right parietal lobe lesion. The findings were most suggestive of a right
parietal lobe abscess. The patient underwent right craniotomy and evacuation of
the right parietal lobe lesion. Pathological evaluation confirmed that the
lesion was an abscess.
The patient was treated with IV antibiotics. During hospitalization, he
underwent biopsy of the right upper lobe lung mass. Pathology revealed
metastatic adenocarcinoma consistent with a rectal primary. Colonoscopy and
flexible sigmoidoscopy showed a large rectal mass that was nearly obstructing
the rectum. The patient is currently undergoing systemic chemotherapy with
concurrent radiation treatment.
A noncontrast head CT was performed in a 57-year- old man with new onset left
facial paresis, leftward tongue deviation and left upper extremity twitching.
An intra-axial mass was present in the right parietal lobe, with surrounding
Courtesy of M Ghesani, MD
In the United States, about 145,000 new cases of large bowel cancer are
diagnosed each year. Of these, about 105,000 are colon, and the others are
The mainstay of treatment for colorectal cancers is surgical resection.
Screening methods, in practice, include fecal occult blood testing, endoscopy
or radiology based on clinical presentation. Based on the timing of
presentation and appropriate workup, diagnosis at an earlier stage of disease
can be made and can reduce cause-specific mortality.
The most common symptoms at presentation are hematochezia or melena,
abdominal pain caused by obstruction or perforation, peritoneal spread, a
change in bowel habits or unexplained microcytic iron deficiency anemia. Other
symptoms include weakness/fatigue and unintentional weight loss. Specifically
for rectal cancer, tenesmus can be a common presentation because the cancer
itself may involve the pelvic floor muscles. Also, neuropathic pain may be
caused by a locally advanced lesion involving the sciatic or obturator nerve.
Given the likelihood for intracranial metastasis, a subsequent CT scan of the
chest, abdomen and pelvis was obtained. Examination of the chest revealed
mediastinal lymphadenopathy with a speculated mass in the right upper lobe (a).
There were two liver nodules suspicious for metastases (not shown). Examination
of the pelvis revealed asymmetric rectal wall thickening with perirectal
infiltration and enlarged perirectal vasculature, suggesting primary rectal
It is estimated that about one-fifth of patients present with distant
metastatic disease. Spread is by either lymphatic or hematogenous
dissemination; however, disease may also spread contiguously. The most common
sites of metastasis are the regional lymph nodes, liver and lungs, as well as
locally in the peritoneum. Specifically, distal rectal malignancies metastasize
primarily to the lungs. It is hypothesized that this is due to hematogenous
dissemination into the venous system, namely the inferior vena cava.
There are also a variety of unusual presentations of colorectal cancer.
These include fever of unknown origin and intra-abdominal, retroperitoneal or
abdominal wall abscesses. Streptococcus bovis bacteremia and
Clostridium septicum sepsis are due to underlying colonic malignancies
in a subset of patients as well.
In this case, the patient presented to the ED with neurologic complaints
and was found to have a mass in the right parietal lobe. In adults, metastases
account for as many as 40% of intracranial masses seen on CT scans, most
commonly lung and breast. The additional chest and abdominal CT findings
supported the likelihood of intracranial metastasis. However, the brain MRI
findings in this patient were more characteristic of an abscess rather than
Figure 3. Contrast-enhanced MRI of the brain
revealed a thin-walled intra-axial lesion situated at the gray-white matter
junction in the right frontal lobe. It was hyperintense on T2-weighted images,
with peripheral intrinsic T1 hyperintensity, which is hypointense on T2
weighted sequence (b). Axial, coronal and sagittal Gadolinium-enhanced images
demonstrated strong peripheral enhancement with no internal enhancement (c).
There was uniform restricted diffusion with corresponding decreased signal on
ADC map associated with the lesion, characteristic of an abscess rather than
All photos courtesy of M Ghesani,
Intracranial abscesses and metastases often show a high degree of
vasogenic edema, as was seen in this case. Abscesses and metastases are
associated with internal low T1 weighted signal, with high T2 signal seen in
abscesses and variable T2 signal seen in metastases. The ring-enhancement
pattern in this patient is also nonspecific; the differential for intracranial
ring-enhancing lesions includes metastatic or primary tumors, radiation
necrosis, multiple sclerosis, lymphoma, resolving infarct and subacute
Metastases enhance in variable patterns, including the ring-like
enhancement classically seen in abscesses. Abscesses are classically associated
with restricted water diffusion, showing increased signal on the
diffusion-weighted imaging series and corresponding signal drop-out on the
apparent diffusion coefficient maps. Metastases usually do not demonstrate
restricted diffusion, although some necrotic tumors (for example, squamous cell
carcinoma) may show restricted diffusion. Finally, the thin rim of low T2 and
high T1 weighted signal characterizes the wall of the abscess and would be
unusual for necrotic tumors. Thickness, irregularity and nodularity are
associated with tumors.
In summary, the MRI findings of restricted diffusion, ring-like
enhancement and the presence of a thin wall with intrinsic T1 signal are all
features that suggest abscess rather than metastasis. The patient underwent
surgical excision of the abscess, and subsequent histological analysis
confirmed the diagnosis.
Amit Patel, MD, is a fellow in oncology at St. Luke’s-Roosevelt
Iwao Tanaka, MD, is a resident in radiology at St.
Luke’s-Roosevelt Hospital Center.
Munir Ghesani, MD, is an attending radiologist at St.
Luke’s-Roosevelt Hospital Center and associate clinical professor of
radiology at Columbia University College of Physicians and Surgeons.
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