AJR 2004; 182:1087-1088
© American Roentgen Ray Society
The Shading Sign in Cerebral Squamous Cell Metastases
Steven W. Hetts,
Joseph P. Urban,
Alfredo Quiñones-Hinojosa,
Dean W. Joelson and
Christine M. Glastonbury
University of California San Francisco, CA 94143
San Francisco Veterans Affairs Medical Center San Francisco, CA
94121
University of California, San Francisco San Francisco General
Hospital San Francisco, CA 94110
A 62-year-old male smoker was taken to the emergency department after being
found unresponsive by his family. Physical examination revealed a thin man who
was confused but without focal neurologic deficit. The admission chest
radiograph showed a right mid-lung opacity for which antibiotic treatment was
initiated with the presumed diagnosis of pneumonia. A later chest CT scan
showed a right upper lobe cavitary mass, which at fine-needle aspiration, was
found to be squamous cell carcinoma. Shortly after beginning antibiotic
treatment, the patient had a grand mal seizure, and a contrast-enhanced head
CT scan showed bilateral rim-enhancing parietal masses with little associated
edema. On MRI, the masses were found to have hyperintense signal on
T1-weighted images and marked hypointense signal on T2-weighted
images—that is, T1 and T2 shortening (Fig.
1A,
1B,
1C,
1D). An external ventricular
drain was placed, but the patient developed progressive hydrocephalus and his
mental status declined. Despite emergent craniotomy and subtotal resection of
the parietal masses, the patient remained unresponsive, and life support was
withdrawn.
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Fig. 1A. —62-year-old man with cerebral squamous cell carcinoma. MR
images show bilateral parietal cystic masses indenting lateral ventricles.
T1-weighted image shows T1 shortening (increased signal intensity) in right
parietal mass.
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Fig. 1B. —62-year-old man with cerebral squamous cell carcinoma. MR
images show bilateral parietal cystic masses indenting lateral ventricles.
T2-weighted image shows focal loss of signal including dependent layer,
representing T2 shading caused by presence of complex blood products.
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Fig. 1C. —62-year-old man with cerebral squamous cell carcinoma. MR
images show bilateral parietal cystic masses indenting lateral ventricles.
Coronal gradient-recalled echo image confirms hemosiderin deposition in
periphery of cystic mass.
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Fig. 1D. —62-year-old man with cerebral squamous cell carcinoma. MR
images show bilateral parietal cystic masses indenting lateral ventricles.
Photomicrograph of histopathologic specimen shows malignant tumor cells
infiltrating brain tissue. Areas of recent hemorrhage and macrophages laden
with yellow hemosiderin pigment indicate chronic bleeding. (H and E,
x40)
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At surgery, the masses were found to be cystic and filled with muddy brown
fluid. Pathologic sections revealed anaplastic squamous cell carcinoma
infiltrating parenchymal vessels. Both acute hemorrhage and hemosiderin were
present, suggesting repeated hemorrhage
(Fig. 1D).
The age of a hematoma is the primary determinant of the nature and form of
blood breakdown products. One of the advantages of MRI is its sensitivity to
the different forms of hemoglobin; for example, T1 shortening is seen with
intracellular or extracellular methemoglobin
[1]. Recurrent hemorrhage with
concentration of proteinaceous and ferrous cyst contents and high viscosity
can result in T2 shortening, which is defined in the MRI literature as
"shading." The shading sign is the loss of signal in a cyst on
T2-weighted images with hyperintense signal on T1-weighted images
[2]. Ovarian cysts can
hemorrhage, but it is the repeated bleeding and reorganization of hemorrhagic
contents in endometriotic cysts that results in T1 hyperintensity and T2
hypointensity. Shading is a sensitive and specific sign of endometriomas that
undergo recurrent hemorrhage in response to cyclic hormonal changes.
Although hemorrhage has been described in a number of different cerebral
metastases including melanoma, choriocarcinoma, bronchogenic carcinoma, and
renal cell, adrenal, hepatocellular, uterine, and thyroid carcinomas, repeated
hemorrhage in cystic metastases is uncommon
[3–6].
In this case of bilateral intracranial cystic squamous cell carcinoma
metastases, recurrent hemorrhage and reorganization of the cystic lesion
produced this characteristic MR signal of hyperintensity on T1-weighted images
and T2 shading, mimicking pelvic endometriomas.
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