Microglioma—Unusual computed tomographic appearance and course of neoplasm

THE JOURNAL OF COMPUTED TOMOGRAPHY

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1983

MICROGLIOMA-UNUSUAL COMPUTED TOMOGRAPHIC APPEARANCE AND COURSE OF NEOPLASM Sudhir

Arora,

M.D.,

Krishna

C. V. G. Rao, M.D.,

Microglioma accounts for 0.8-1.5% of primary brain tumors. Eight cases of primary Iymphoma of 50% of the patients demonbrain are presented. strated unusual computed tomographic appearances. These patients were divided into three groups depending on clinical outcome. Survival seems to be related to treatment modality. Longest survival times were in patients treated with radiafion alone or radiation following biopsy.

KEY WORDS:

Computed tomography; Primary lymphoma; Reticulum cell sarcoma; Microglioma; Brain

Various synonyms such as microgliomas, primary reticulum cell sarcomas, and histiocytic lymphoma have been used to describe the tumor characterized by lymphoma-like cells confined to the central nervous system. This entity accounts for 0.8-1.5% of primary brain tumors (1, 2). Immunosuppressed allograft recipients are at increased risk for this tumor (3-5). The characteristic computed tomography (CT) findings previously reported (6-11) are markedly enhancing lesion confined to the basal ganglia, thalamus, corpus callosum, frontal region and vermis cerebelli. In untreated cases mean survival after onset of initial symptoms is few months (1, 2). From the Section of Neuroradiology, Department of Diagnostic Radiology, University of Maryland Hospital, Baltimore, Maryland. Address reprint requests to: Sudhir Arora, MD, Section of Neuroradiology, Department of Radiology, Howard University Hospital, 2041 Georgia Avenue NW, Washington, DC 20060. Received October 14, 1982. Accepted January 27, 1983. 0 1983 by Elsevier Science Publishing Co., Inc. 52 Vanderbilt Ave., New York, NY 10017 0149-936X/83/$3.00

and

Fouad

Gellad,

M.D.

Eight cases of microglioma followed with sequential CT examination for up to’five years are reported. Unlike previously reported series (6-12), the present series deals with dissimilar CT findings and the course of the neoplasm.

CLINICAL

MATERIAL

From 1977 to 1982, eight cases with CT and clinical findings indicative of microglioma were seen at University of Maryland Hospital. In all eight cases more than one CT study was performed. Six patients also had radionuclide and angiographic studies. Surgical excision or biopsy of the lesion was available in seven cases. In the remaining patient, biopsy was not performed due to the location of the lesion in the dominant hemisphege. The average age in this series of eight cases was 48 years, with a range of 31 to 48 years. Four patients were male and four were fe$nale. The patients were divided into three groups reiflecting their clinical outcome (Table 1). GROUP

1

Case 1 SM, 58-year-old female with a 2.5-year history of right frontoparietal headaches, underwent CT in October and November 1977. The CT studies demonstrated partial obliteration of fltontal horn of right lateral ventricle. No enhancement was noted after intravenous contrast administration (Figure 1).Radionuclide study showed no evidence of tumor. Biopsy and subtotal right frontal lobectomy was done. Histologic studies showed marked increase of cellularity, consisting of dark routid small cells with no discernible cytoplasm infiltrating diffusely within the parenchyma around the capillaries and

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TABLE 1. Management

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and Outcome

Case Sex

CT findings

Angiogram

58

F

-

Normal

2

46

F

Avascular

Normal

3

52

M

4

56

M

5

48

F

Nonenhancing right frontal lesion Nodular enhancing right frontoparietal lesion Nonenhancing right thalamic lesion Homogeneously enhancing left parasagittal lesion Homogeneous enhancement in left internal capsule

no. Group l-Excision 1

Group 2-Biopsy 6

7

Group J-Medical 8

Age

Radionuclide

scan

and Radiation

and Radiation 50

31

Treatment 48

-

-

Avascular

-

Relatively vascular

Large area of abnormal uptake

M

Nonenhancing mass right parietal

Avascular

Normal

M

Enhancing mass right parietal

Avascular

Normal

F

Nonenhancing mass left basal ganglia

Avascular

Normal

neurons, consistent with a pathologic diagnosis of reticulum cell sarcoma. The patient received whole brain irradiation. A CT study in January 1978 after treatment with 5000 rads over five weeks showed irregular ring enhancement with some areas of low density in the right frontal region causing partial obliteration of right frontal horn (Figure 2). Three months after surgery the patient exhibited increasingly bizzare behavior and had difficulty controlling urination, She received a course of chemotherapy (CCNU, doxorubicin hydrochloride [Adriamycin], cyclophosphamide [Cytoxan], dexamethasone [Decadron]). Subsequent CT studies in May and June 1978 showed an increase in volume of the enhancing mass with surrounding edema in right frontal region. Follow-up CT in July and August 1978 demonstrated further extension of the tumor in midfrontal region. The patient was readmitted to hospital in September 1979 in a vegatative state. She died in January 1980.

Case 2 SO, 46-year-old woman was admitted with history of seizure. Electroencephalogram showed epileptogenie focus in right temporoparietal region. A CT study done on July 8, 1975 showed a small enhancing nodular density with surrounding edema in right frontoparietal region. Angiography on July 13, 1975 showed an avascular mass in right parietal region A radionuclide scan on July 23, 197.5 showed normal findings. Subtotal resection of lesion was carried out on July 25, 1975. Microscopy revealed diffuse infiltration of white matter by small anaplastic cells of different sizes and shapes with scanty eosinophilic cytoplasm and dark nuclei. In some places, small groups of cells that generally resembled neoplastic microglial cells were seen. After surgery, the patient received 4000 rads to the total brain over four weeks and 1000 rads small field irradiation over one week with a 4 MEV machine.

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In April 1976 CT studies showed a nodular enhancing density with surrounding; edema. The patient was readmitted to the hospital with reduced mentation and left hemiplegia. Right carotid angiography done on July 25, 1976 showed a large, relatively vascular ~frontoparietal tumor. Tumor blush and an early draining vein were noted. The patient died in August ‘1976.

Case 3

FIGURE 1. Case onstrates partial lateral ventricle. right frontal lobe

l.(A) NNCT [contiguous sections] demobliteration of frontal horn of the right (B) CECT shows no enhancement of the lesion,

FIGURE 2. Case 2. CECT (contiguous sections) two obtained months after surgical excision and irradiation shows a large peripherally enhancing lesion in the right frontal lobe. Note the change in enhancement characteristic as well as increase in size of the lesion.

GH, 52-year-old man presented in May 1977 with four-day history of constant dull aphing sacral pain. A lumbar puncture revealed evidence of lymphomatous leptomeningitis. He was; treated with intrathecal and systemic cyclophosphamide (Cytoxan), vincristine, and prednisone. A cranial CT study showed normal findings. The patient was readmitted in November 1977 with hemiparesis and seizure. A !CT study done at that time revealed a nonenhancing hyperdense mass in right posterior thalamic region [Figure 3). In light of the history of lymphomatous leptomeningitis, the patient was given 3000 rads total brain irradiation. In February 1978 the patient presented with mild lethargy and dysphasia. A CT study showed a large enhancing left frontoparietal lesion with marked surrounding edema i(Figure 4). No significant ventricular compression was noted, The patient underwent left frontoparietal craniotomy and two thirds of the tumor was removed. Pathologic examination was consistent with that of poorly differentiated lymphoma. After surgery the patient was

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treated with another 3000 rads total brain irradiation A small residual tumor was noted on subsequent CT. In April 1978 the patient was readmitted with lethargy and right hemiparesis. Marked increase in tumor size and surrounding edema was noted on CT. The patient had a progressive downhill course and died in May 1978.

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Case 4 AS, 56-year-old man was admitted with history of gradual onset of right-sided weakness. On physical examination, early blurring of disc margins bilaterally and right hemiplegia was noted. A CT study demonstrated an isodense lesion with surrounding low density in the left parasagittal region with homogeneous enhancement following

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contrast administration. Angiography demonstrated a relatively avascular mass involving the cingulate gyrus on the left side. Left parietal craniotomy was done and 3.2 X 2.4 X 1.8 cm of tumor tissue was removed. Histologic studies indicated reticulum cell sarcoma. After surgery the patient received 5000 rads whole brain irradiation over five weeks. The patient is alive following one course of radiation therapy. Case 5 TD, 48-year-old woman with a six-month history of progressively inceasing confusion, inappropriate behavior, and headaches was found to have bilateral papilledema upon physical examination. Radionuclide scan showed a large area of abnormal uptake in the left frontopatietal region. Carotid angiography demonstrated a large, relatively vascular mass in the left basal ganglia. A CT study revealed a large ring enhancing lesion in the left caudate nucleus and internal capsule area [Figure 5). On February 8, 1979 the patient underwent a resection of tumor. After surgery the patient developed right hemiplegia and global dysphasia. Over a prolonged postoperative period the right arm remained plegic but the right leg began to move spontaneously with poor stength. Her global dysphasia resolved. The patient underwent 6300 rads of brain irradiation. Computed tomography studies on Feb-

FIGURE 5. Case 5. Computed tomography scans before (C- ) and after (C+) contrast enhancement. Noncontrast CT shows a hyperdense lesion in left caudate nucleus and internal capsule CECT shows intense enhancement of the lesion.

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a ruary 26, 1979 and March 12, 1979'demonstrated low density area considered to represent postsurgical gliosis.

GROUP 2 Case 6 MH, a 50-year-old man with six-year history of seizures, presented in May 1975 withileft hemiparesis. A CT study on May 4, 1975 demonstrated a nonenhancing low density area in righit parietal region with minimal indentation of body of right lateral ventricle (Figure 6). A radionuclide scan on May 9, 1975 indicated normal findings. Right carotid angiogram on May 15, 1975 demonstrated an avascular mass in right posterior parietgl region. Repeat radionuclide scan on October 2, 1975 again showed normal findings. The CT study and pneumoencephalogram demonstrated the mass indenting the body of the right lateral ventricle (Figure 7). Biopsy of the lesion on October 9, 1975 demonstrated diffuse cellular infiltrate involving both cortex and white matter. Most of the cells were cheracterized by a slightly and irregularly indented, huge nucleus exhibiting a large nucleolus. Cells were diffusely scattered among the neurophil or were arranged in perivascular fashion. After surgery the patient received 5000 rads total brain over five weeks. Follow-up CT scans in April 1980, February 1981, and March

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Case 7 OJ, 31-year-old man, was admitted in June 1976 with 1.5-year history of seizures. On admission, neurologic examination showed normal findings. The radionuclide scan also demonstrated normal findings. A CT study showed an isodense area surrounded by zone of low density and showing homogeneous enhancement, often contrast administration, in right parietal region (Figure 8). The right lateral ventricle was compressed. Right carotid angiogram on July 1, 1976 demonstrated minimal shift of anterior cerebral artery. Insular branches of the right middle cerebral artery were slightly splayed. The posterior parietal and temporal arteries were slightly stretched. Internal cerebral vein was shifted 8 mm from midline. Early draining into the internal cerebral vein was noted. A biopsy of the lesion revealed evidence of microglioma. The patient received whole brain irradiation of 5000 rads over five weeks. Further follow-up was not possible because the patient left the country. FIGURE 7. Case 6. Pneumoencephalogram demonstrated indentation of roof (arrow) of right lateral ventricle.

GROUP

3

Case 8 1982 show focal area of low density in right parietal region. At present the patient suffers from frontal lobe syndrome and lower extremity weakness. He is receiving phenytoin (Dilantin) and primidone (Mysoline).

CD, 45-year-old woman, was admitted with a history of an episode of nocturnal seizure. Neurologic examination at time of admission showed normal findings; a radioisotope scan was within normal limits; and an electroencephalogram revealed left temporoparietal focus. A visual field examination

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revealed a mild left temporal field defect. On CT a nonenhancing mass in the left basal ganglia was found (Figure 9). The CT findings were thought to represent either a low grade neoplasm or the result of an infarct. Subsequent CT studies revealed similar findings as the initial CT study. The patient is being treated with phenytoin (Dilantin) and mild doses of steriods to control seizures. Angiography demonstrated an avascular mass.

FIGURE 8. Case 7. Computed tomography scans before (C-) and after [C+) contrast enhancement shows an isodense lesion with surrounding edema in the right parietal lobe. Homogeneous enhancement of the lesion is seen after contrast administration.

FIGURE 9. Case 8. CECT (contig-

uous sections) shows hypodense, nonenhancing mass in the left hemisphere. Contralateral shift of the midline structures is seen.

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DISCUSSION Microgliomas are characterized by perivascular or parenchymal infiltration of primitive reticulum cells on histologic study. Microgliomas are presently considered by many pathologists as being synonymous with histiocytic lymphomas or reticulum cell sarcoma, a rare form of primary intracranial neoplasm. Based on one large series of 83 cases, the

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neoplasm was multifocal in 44% and solitary in 56% of cases (1). In comparing the CT features and reviewing previously reported cases, it appears that no specific CT patterns can be considered characteristic of microglioma on the preenhanced scan. The lesion can be hypodense (8, 9), isodense (7, 8, ll), or hyperdense (6, 10). In previous reports the lesions have been characterized as having uniform enhancement (6-12). It is interesting to note, however, that in nearly 50% of the cases reported here and in one of the four cases reported by Tadmor et al (8), the neoplasm did not show enhancement on postcontrast CT, although there was definite evidence of mass. These findings when seen on the initial CT may be mistaken for region of infarction, especially when they involve the thalamus or basal ganglia. Unlike infarction, however, the hyposdense lesion of microglioma may not show evidence of further gliosis on subsequent sequential CT studies. The nonenhancement in some of our cases could not be attributed to differing cellular architecture or neovascularity, as with different grades of astrocytoma, because the histologic patterns of enhancing and nonenhancing lesions were similar in pathologic studies of our cases. Another feature in our small series was the rapid invasiveness of the neoplasm, as demonstrated on CT by marked enhancement in patients who underwent surgical excision followed by radiation therapy. A better outcome was noted in two of the eight patients who had radiation therapy as the primary modality of treatment following tissue diagnosis by surgical biopsy. SUMMARY

The CT characteristics of microglioma can be variable. Enhancement is not characteristic in microglioma. Survival seems to be related to treatment modality. Longest survival is in patients treated with radiation alone or following biopsy. REFERENCES 1. Henry JM, Heffner RR, Dillacd SH, et al: Primary malignant

lymphomas of the central nervous system. Cancer 1974; 34:1293.

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2. Schaumberg HH, Plank CR, Adams RD: The reticulum cell sarcoma-microgliomas group of brain tumors. Brain 1972; 95:199-212. 3. Barnett LB, Schwartz E: Cerebral retriculum cell sarcoma after multiple renal transplants. J Neural Neurosurg Psychiatry 1974; 37:966-70. 4. Cho ES, Connolly E, Porro RS: Primary reticulum cell sarcoma of the brain in a renal transplantation recipient. J Neurosurg 1974; 41:235-g. 5. Jellinger K, Radaszkiewicz T: Involvement of the central nervous system in malignant lymphomas. Virchow Arch (Path01 Anat) 1976; 370:345-62. 6. Thomson JLG, Brownell B: Computed tomographic ance in microglioma. Clin Radio1 1981; 32:367-74.

appear-

7. Enzmann DR, Kirkorian J, Norman D, et al: Computed tomography in primary reticulum cell sarcoma of the brain. Radiology 1979; 130:165-70. 8. Tadmor R, Davis KR, Roberson GM, Kleinman GH. Computed tomography in primary malignant lymphoma of the brain. J Comput Assist Tomogr 1978; 2:135-40. 9. Kazner E, Wilske J, Steinhoff NS, Stochdroph 0. Computer assisted tomography in primary malignant lymphomas of the brain. J Comput Assist Tomogr 1978; 2:125-34. 10.Radvany J, Levine M. Computed tomography in the diagnosis of primary lymphoma of the central nervous system. J Comput Assist Tomogr 1978; 2:215-17. 11. Tallroth K, Kalevuo K, Holsti L, Anderson LJ. Angiography and computed tomography in the diagnosis of primary lymphoma of the brain. Clin Radio1 1981; 32:383-8. 12. Zawdzki MB, Enzmann DR. Computed tomographic scanning in patients with lymphoma. Radiology 129:67-71.

brain 1978;

CONTINUING MEDICAL EDUCATION QUESTIONS 1. Microgliomas brain tumors?

account

% of primary

for

a. 0.1-0.5°/0. b. 0x-1.5%. c. 1.8-3.5%. d. 4-a%.

2. Microgliomas

are often confined a. Basal ganglia. b. Thalamus. c. Vermis. d. All of the above.

3. Microglioma on noncontrast a. Hypodense. b. Isodense. c. Hyperdense. d. All of the above.

to

CT may appear