DOI:10.2214/AJR.07.7040
AJR 2008; 191:S31-S33
© American Roentgen Ray Society
AJR Teaching File: Lump on the Head
Stephen M. Sabourin1,
Ashok Jayashankar and
Mark E. Mullins
1 All authors: Department of Radiology, Emory University School of Medicine,
1364 Clifton Rd. NE, Atlanta, GA 30322.
Received September 12, 2007;
accepted after revision April 25, 2008.
Address correspondence to S. M. Sabourin
(ssabour{at}emory.edu).
Keywords: postirradiation osteosarcoma • retinoblastoma • secondary osteosarcoma • second malignant neoplasm
Clinical History
A 23-year-old man presents with a lump on the left side of his head. The
patient had undergone enucleation and radiation therapy for retinoblastoma
(RB) as a child.
Radiologic Description
Unenhanced axial CT images of the head through the level of the foramen
magnum using soft-tissue (Fig.
1A) and bone (Fig.
1B) algorithms show an aggressive, densely ossified bone-forming
tumor that involves portions of the left temporal and greater sphenoid bones.
The right globe prosthesis is a significant finding because it is suggestive
of the cause of the mass. The left-sided mass is consistent with the provided
clinical history of a palpable lesion. An axial T1-weighted
gadolinium-enhanced image through the same level
(Fig. 1C) confirms a large mass
with an ill-defined enhancing soft-tissue component.
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Fig. 1A —23-year-old man with lump on left side of his head.
Unenhanced axial CT images of head through the level of the foramen magnum
using soft-tissue (A) and bone (B) algorithms demonstrate an
expansile bone-forming mass involving portions of the left temporal and
greater sphenoid bones (arrows, B) and a right globe
prosthesis (arrow, A).
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Fig. 1B —23-year-old man with lump on left side of his head.
Unenhanced axial CT images of head through the level of the foramen magnum
using soft-tissue (A) and bone (B) algorithms demonstrate an
expansile bone-forming mass involving portions of the left temporal and
greater sphenoid bones (arrows, B) and a right globe
prosthesis (arrow, A).
|
|
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Fig. 1C —23-year-old man with lump on left side of his head. Axial
T1-weighted gadolinium-enhanced MR image through the level of the cavernous
sinus demonstrates a large heterogeneously enhancing mass with intraorbital
(long straight arrow), intracranial (arrowhead), and
extracranial (short straight arrow) extension.
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The lesion shows dense mineralization and an ill-defined soft-tissue
component suggestive of a high-grade malignancy. The right globe prosthesis
reminds us that the patient has a significant medical history and that the
cause of this skull-based tumor may be primarily or secondarily related to the
history of retinoblastoma—for example from metastasis, treatment-related
malignancy, or de novo neoplasm.
Differential Diagnosis
The differential diagnosis for an aggressive-appearing sclerotic entity
involving the craniofacial bones includes Paget's disease, osteosarcoma,
chondrosarcoma, osteomyelitis, fibroosseous lesions such as ossifying fibroma
and fibrous dysplasia, metastasis and intraosseous meningioma.
Given the imaging characteristics of this lesion and the clinical history,
a focused differential diagnosis for this case includes osteosarcoma (de novo
or radiation-induced), metastasis (from retinoblastoma or a second malignant
neoplasm), intraosseous meningioma, Paget's disease, and infection.
Retinoblastoma metastatic disease usually presents with local extraocular
extension, and the time interval between diagnosis and treatment of the
primary disease mitigates against this representing recurrent retinoblastoma.
The patient could have a second primary malignancy that has metastasized or a
de novo primary neoplasm. Because patients with retinoblastoma are genetically
predisposed to developing malignancies, most commonly osteosarcoma, a de novo
osteosarcoma is a reasonable consideration. Rarely, intraosseous meningioma
may have this aggressive appearance. Osteosarcoma arising in pagetoid bone is
unlikely given the patient's age and unilateral distribution, with Paget's
usually having a bilateral manifestation in the skull. Although infection can
be an aggressive lesion, it is unlikely to have this bone-forming appearance.
Further review of the patient's history revealed that he was treated with
enucleation of the right globe and irradiation of the left globe for
retinoblastoma as a child. Radiation therapy has been linked to both
osteosarcoma and meningioma formation.
Diagnosis
Postirradiation secondary osteosarcoma is the most likely diagnosis after
review of surgical pathology and in conjunction with the clinical history of
radiation therapy to the left globe.
Commentary
Osteosarcoma is the second most frequent malignant bone tumor after
multiple myeloma [1]. Primary
osteosarcoma typically presents in the metaphysis of long bones; however, this
tumor can occur in any part of the skeleton
[1]. Osteogenic sarcoma of the
head and neck region is infrequent, accounting for less than 10% of reported
cases [2]. Postirradiation
sarcomas usually occur after treatment of soft-tissue tumors, and they
typically arise in osseous structures
[1,
3].
Regarding postirradiation osteosarcoma, the age of the patient at the time
of diagnosis depends on the age at which the patient first received radiation
treatment [4,
5]. The latency period
typically averages approximately 15 years but can range from 3 to 65 years
[1,
3–5].
Some studies have found a slightly shorter latency period associated with
chemotherapy administration
[4], whereas others have found
no association [5].
Development of postirradiation sarcomas is a recognized complication of
treatment, showing a wide range of prevalence—0.02–5.5% of all
sarcomas—with the most common histologic subtypes being osteosarcoma,
malignant fibrous histiocytoma, and fibrosarcoma
[1,
3,
4]. Secondary transformation of
osseous and soft-tissue osteosarcomas arising from benign lesions represents
5–7% of all osteosarcomas
[1]. Common nonocular second
tumors in children with retinoblastoma include osteosarcoma, malignant fibrous
histiocytoma, angiosarcoma, and rhabdomyosarcoma
[5–9].
In this case, the patient had a history of retinoblastoma treated with
enucleation of the right eye and irradiation to the left eye. Retinoblastoma
is caused by a loss of function of a tumor suppressor gene, the RB1
gene, located on the long arm of chromosome 13
[10,
11]. Children with the
familial form of retinoblastoma inherit a mutated form of the RB
gene, placing them at a significantly increased risk for developing the
disease. They also have a propensity to develop second nonocular malignancies,
the most common of which is osteosarcoma
[8–12].
In patients with familial retinoblastoma, the relative risk of developing a
second malignant tumor increases over time
[5,
6,
13].
Although the occurrence of second malignant tumors is well recognized,
there is some controversy regarding their cause
[5]. Determining whether a
second malignant neoplasm is causally related to radiation therapy,
chemotherapeutic agents, or the underlying genetic predisposition of the
patient is difficult. Initial reports attributed the increased incidence to
irradiation treatment, but subsequent reports discovered second nonocular
malignancies in retinoblastoma patients who had not undergone irradiation
[6]. Second nonocular tumors
that occur below the neck of patients who had radiation therapy are unlikely
to be radiation-associated [6].
The study by Mohney et al. [5]
found that in 60 patients with familial retinoblastoma treated with
irradiation, 14 patientsdeveloped a second nonocular neoplasm, but in only
four of those 14 was the neoplasm in the field of irradiation. Some proposed
explanations for these differences include higher doses of radiation in
initial published reports, variations in irradiation technique, the use of
chemotherapeutic agents and their dosages, as well as published studies with
relatively short-term follow-up
[5].
The investigation by Mohney et al.
[5] regarded tumors occurring
in or immediately surrounding the orbit of the irradiated eye to be
radiation-associated. In our patient, the tumor occurred in the radiation
portal of the left eye, lending confidence to the final diagnosis of
postirradiation osteosarcoma. Lower doses at the periphery of the radiation
portal result in damage to the reparative mechanisms without devitalization of
the tissue, putting these regions at the most increased risk for tumor
formation [1,
4]. The prognosis of these
tumors is poor, with radical surgical resection the mainstay of treatment
[1,
3,
4].
Clinical presentation usually involves localized pain or a palpable mass
[2]. Radiologic evaluation of
craniofacial masses is typically performed with CT and MRI to characterize the
lesion and to fully evaluate the extent of the tumor for preoperative
assessment before debulking surgery
[2].
Typical radiologic findings associated with postirradiation bone sarcomas
include a soft-tissue mass, bone destruction, tumor matrix mineralization, and
periosteal reaction, in descending order of occurrence
[1–4].
Tumor matrix mineralization and cortical bone destruction are best evaluated
with CT [2,
4]. MRI is superior for
defining the soft-tissue component and the extent of the lesion
[1,
4]. Imaging features and
pathology cannot distinguish between a spontaneous (de novo, primary) and a
secondary osteosarcoma malignancy
[1,
3,
4]. Clinical history, radiation
dose, latency period, and a histologically proven malignant tumor arising in
the field of irradiation must all be considered to reach a presumptive final
diagnosis of postirradiation osteosarcoma
[3,
4].
Concerning our patient, the history of radiation treatment for
retinoblastoma as a child should raise suspicion for a postirradiation
complication. Even if a full therapeutic radiation history is not available,
an appreciation of the expected latency period may help to suggest the
diagnosis of a secondary tumor. The imaging findings are characteristic of an
osteosarcoma: the enhancing soft-tissue mass, mineralization pattern, and
destruction of surrounding bone. MRI is the standard imaging technique for
local staging and surgical planning to ascertain the proximity and involvement
of tumor with nerves, vessels, and other vital structures. Infection is
frequently a consideration with aggressive, destructive lesions, and may have
unusual presentations but it would not have this bone-forming appearance.
Objective
The objective of this article is to review the typical clinical setting and
radiologic findings associated with postirradiation osteosarcoma.
Conclusion
This patient has an appropriate clinical and radiation history and
characteristic imaging findings, allowing a presumptive diagnosis of
postirradiation osteosarcoma to be made, with a relatively short differential
diagnosis. Radiologists should be familiar with long-term complications
associated with neoplastic syndromes and antineoplastic therapies.
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Clinical History
Radiologic Description
