AJR 2004; 183:1169-1171
© American Roentgen Ray Society
Primary Oat Cell Carcinoma of the Breast: Imaging Features
Antonio Mariscal1,
Elda Balliu1,
Rocío Díaz1,
J. Darío Casas1 and
Ana María Gallart1
1 All authors: Department of Radiology, Hospital Universitari Germans Trias i
Pujol, Carretera de Canyet s/n, Badalona E-08916, Spain.
Received August 6, 2003;
accepted after revision March 22, 2004.
Address correspondence to A. Mariscal
(mariscal{at}ns.hugtip.scs.es).
Introduction
Anaplastic small cell carcinoma (oat cell carcinoma) is the most aggressive
variant of neuroendocrine tumors. Oat cell tumors occur generally in the lung
and exceptionally in the breast. We present the case of a patient with primary
oat cell carcinoma of the breast and report the imaging findings. To our
knowledge, this case is the first in which the sonographic and MRI features of
this entity are described.
Case Report
A 53-year-old woman with no relevant medical history was evaluated because
of a rapidly growing lump in the right breast for the previous 3 months. At
physical examination, a hard nodule, approximately 5 cm in diameter in the
axillary prolongation of the breast, adhering to deep planes and with minimal
skin retraction was detected. A hard mobile mass, approximately 4 cm, was
palpated in the right axilla. Neither relevant signs nor symptoms were found
at the physical examination. Mammography revealed a round 5 x 5 cm mass
that was denser than the surrounding parenchyma and showed partially
well-circumscribed and microlobulated margins in the axillary tail of the
right breast. On the mediolateral oblique view, an enlarged dense axillary
lymph node was partially visualized in the axillary region
(Fig. 1A). A sonographic study,
obtained using a 7.5-MHz linear transducer, depicted the breast lesion as a
solid hypoechoic mass with low homogeneous echoes, mild posterior acoustic
enhancement, and a microlobulated contour
(Fig. 1B); this mass was highly
suspected to be malignant. An enlarged (4-cm) hypoechoic lymph node with no
fatty hilum was visualized in the axillary region and was suspected to be
metastatic.
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Fig. 1A. —53-year-old-woman with rapidly growing breast mass. Right
mediolateral oblique mammogram shows round mass in axillary tail of breast.
Margins are partially obscured by adjacent normal breast tissue. Enlarged
dense lymph node is partially visible adjacent to lesion in lower axillary
region.
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Mammographic MRI was performed on a 1.5-T unit using a bilateral dedicated
breast coil with the following sequences: axial T2-weighted turbo spin-echo
and coronal dynamic T1-weighted fast field-echo after gadolinium injection
(dose, 0.16 mmol/kg; injection rate, 2 mL/sec). A 2-mm slice thickness was
used, and postprocessing of the image from the dynamic study with subtraction
techniques was performed. Maximum-intensity-projection and multiplanar
reconstructions and time–intensity curves of the lesion signal were
obtained. MRI revealed a 5.5 x 3.5 cm lesion with rounded morphology and
well-defined, partially microlobulated borders that enhanced during the early
phases of the dynamic study (Figs.
1D and
1E). The time–intensity
curve of the signal showed marked early enhancement of the lesion, suggesting
malignancy (Fig. 1F). No other
lesions were detected in the right breast or contralateral breast.
Fine-needle aspiration biopsy of both masses was performed. Cytology
revealed loosely cohesive cell groups of varying size with hyperchromatic
nuclei and evident molding, which is consistent with oat cell carcinoma
(Fig. 1G). Tissue obtained with
sonographically guided core biopsy showed morphologic characteristics
identical to those found in the samples from fine-needle aspiration biopsy.
The findings for the immunohistochemical study were positive for
synaptophysin, which is a specific marker for tumors of endocrine origin, and
negative for thyroid transcription factor-1, which is a sensitive, specific
diagnostic marker for oat cell carcinoma of the lung and adenocarcinoma.
Cytology of the axillary lymph node showed similar characteristics.
On chest and abdominal CT, performed as part of staging, the right breast
mass and enlarged axillary lymph node were also visible
(Fig. 1H) and there was no
evidence of lesions consistent with extramammary oat cell carcinoma
(particularly of the lung) or of distant metastasis.
Neoadjuvant chemotherapy was initiated with cisplatin and VP-16. After four
cycles of chemotherapy the patient experienced complete clinical remission.
Mammography, sonography, and MRI showed near resolution of the lesions
described. Given the good clinical and radiologic response, the tumor and
axillary lymph nodes were resected. Examination of the surgical specimens
showed fibrosis and fibrocystic mastopathy changes with no evidence of
residual neoplasm. Subcapsular micrometastasis was observed in one lymph node.
The patient is alive and shows no evidence of local recurrence or extramammary
disease 6 months after treatment.
Discussion
Neuroendocrine tumors comprise a spectrum of lesions that range from
relatively unaggressive types, such as carcinoid tumor, to highly aggressive
ones, such as oat cell carcinoma
[1]. The prognosis of patients
with primary oat cell carcinoma of the breast is uncertain, and the stage of
the disease at the time of diagnosis is a determinant factor in its evolution
[2].
Oat cell carcinoma can occur in various locations, with the lung being the
most common [3]. This tumor
rarely affects the breast, and cases have been documented only sporadically in
the literature [2,
4,
5]. The mammographic findings
have been reported in only one case to our knowledge. That lesion was
described as a 3.5 x 3.5 cm lobulated mass with partially smooth and
partially ill-defined margins
[4], features similar to those
observed in our patient. Sonographic and MRI findings have not, to our
knowledge, been described previously. In our patient, sonographic study showed
a solid hypoechoic breast lesion with slight posterior acoustic enhancement.
MRI revealed a partially well-defined round mass, with a somewhat
microlobulated contour that enhanced on the dynamic study. These radiologic
findings are not specific, but they met the criteria of suspected malignancy
and therefore warranted cytohistologic study.
Cytology results from fine-needle aspiration biopsy disclose the
characteristic features of these tumors but cannot be used to determine the
primary or metastatic nature of the lesions
[6]. Histologic study of core
needle or surgically biopsied tissue can support the diagnosis of primary oat
cell if the in situ neuroendocrine component is observed
[2]. Because pulmonary
carcinoma often metastasizes to the breast, this possibility should be ruled
out by a staging study [7,
8]. The differentiation between
primary and metastatic neoplasms is essential for planning treatment to avoid
unnecessary radical interventions
[2,
4]. Immunohistochemical study
in our patient identified an oat cell–type neuroendocrine neoplasm of
probable extrapulmonary origin. The findings from the staging study were
negative.
Establishing the most suitable treatment in these patients is difficult
because the number of reported cases is still low
[4]. Because our patient had a
locally advanced carcinoma, she received neoadjuvant chemotherapy according to
the guidelines for pulmonary oat cell carcinoma used in our
hospital—that is, cisplatin and VP-16. The chemotherapeutic agents used
to treat an oat cell carcinoma differ from those that would be used to treat
an invasive ductal carcinoma of the breast, a more common malignancy. After
the patient showed excellent clinical and radiologic response, conservative
surgical treatment was performed.
In summary, primary oat cell carcinoma of the breast presented nonspecific
mammographic, sonographic, and MRI features in our patient. The case we
describe is an example of a rare entity in the breast in which percutaneous
core needle biopsy is important in establishing a diagnosis and, therefore, in
treating the patient. Any information that can be gained about this rare
condition is useful for its characterization. Descriptions of new cases are
necessary to determine the radiologic presentation of primary oat cell
carcinoma of the breast, assess treatments to find the most suitable one, and
determine the prognosis of affected patients.
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Fig. 1C. —53-year-old-woman with rapidly growing breast mass. Coronal
T2-weighted turbo spin-echo image shows partially well-defined round mass with
somewhat microlobulated margins and predominantly hyperintense heterogeneous
signal located in axillary prolongation of right breast.
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