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Sep 25, 2015 - Seungbaek Hong, MD1, Yeon Joo Jeong, MD1, Geewon Lee, MD1, ... MD2, Chang-Hoon Lee, MD3, Ah Rong Kim, MD3, Ji Won Lee, MD1*.
Case Report pISSN 1738-2637 / eISSN 2288-2928 J Korean Soc Radiol 2016;74(4):226-229 http://dx.doi.org/10.3348/jksr.2016.74.4.226

Dynamic Computed Tomography Findings of Atypical Pulmonary Hamartoma and It’s Pathologic Correlations: A Case Report 비전형적 폐과오종의 역동성 전산화단층촬영 소견과 그 병리학적 연관성: 증례 보고 Seungbaek Hong, MD1, Yeon Joo Jeong, MD1, Geewon Lee, MD1, Yeong Dae Kim, MD2, Hyo Yeong Ahn, MD2, Chang-Hoon Lee, MD3, Ah Rong Kim, MD3, Ji Won Lee, MD1* Departments of 1Radiology, 2Thoracic and Cardiovascular Surgery, 3Pathology, Medical Research Institute, Pusan National University Hospital, Busan, Korea

We present the dynamic contrast-enhanced computed tomography (CT) findings of atypical pulmonary hamartoma with a rare histologic pattern in a 20-year-old male. CT showed a 3.4 cm lobulated mass with a ‘tip of the iceberg’ appearance in the medium bronchus of the right lower lobe. Dynamic contrast-enhanced CT demonstrated a heterogeneously and persistently enhancing mass. The CT Hounsfield unit (HU) measurements were: 17 HU pre-contrast, 32 HU at 1 minute, 44 HU at 2 minutes, 51 HU at 4 minutes, and 64 HU at 15 minutes. Pathologic examination after video-assisted thoracoscopic surgery disclosed a pulmonary hamartoma with a predominant fibroblastic component. Index terms Hamartoma Lung Multidetector Computed Tomography Fibroblast

INTRODUCTION

Received July 23, 2015 Revised August 25, 2015 Accepted September 25, 2015 *Corresponding author: Ji Won Lee, MD Department of Radiology, Medical Research Institute, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan 49241, Korea. Tel. 82-51-240-7354 Fax. 82-51-244-7534 E-mail: [email protected] This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

pathologic findings. This case report was approved by our Institutional Review Board.

Pulmonary hamartoma is the third most frequent cause of solitary pulmonary nodules with an overall prevalence of up to 5.7% (1), and chondromatous hamartoma is the most common type

CASE REPORT

of pulmonary hamartoma (2). Masses are composed of abnormal

A 20-year-old male was referred to our hospital for exertional

mixtures of epithelial and mesenchymal elements, such as carti-

dyspnea of two weeks’ duration. Clinical examination and rou-

lage, fat, fibromyxoid tissue, smooth muscle, and bone (3, 4).

tine laboratory test results were unremarkable, but chest radiog-

In spite of its relative frequency, no report has been published

raphy revealed a lobulated mass in the right lower lung field (Fig.

that details the CT findings of pulmonary hamartomas with rare

1). Non-enhanced CT showed a 3.4 cm lobulated mass without

pathologic patterns, such as fibrous or fibroleiomyomatous

evidence of fatty deposits or calcification. The mass was posi-

types. Here, we describe, for the first time, the unusual contrast-

tioned near the medium bronchus in the posterior basal seg-

enhanced CT findings of pulmonary hamartoma with a pre-

ment of the right lower lobe. It had a large extrabronchial com-

dominant fibroblast component and their relations with histo-

ponent and a small endobronchial component, that is, a ‘tip of

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Seungbaek Hong, et al

A

B Noncontrast 0.5 min

(HU) 70 60 50 40 30 20 10 0

C

1 min

2 min

5 min

15 min

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 (min)

D E Fig. 1. 20-year-old male with pulmonary fibroblastic hamartoma. A. Chest radiograph demonstrating the presence of a lobulated mass in the right lower lung field. B. Axial contrast-enhanced chest CT image with mediastinal setting (left) and oblique two-dimensional coronal reformatted image with lung setting (right) showing a 3.4 cm mass in the posterior basal segment of the right lower lobe. The mass consists of small endobronchial (arrows) and large extrabronchial components, suggestive of the ‘tip of the iceberg’ sign. C. Dynamic contrast-enhanced CT image showing persistent enhancement with a net enhancement of 47 Hounsfield units (HU). Non-contrast CT provides no evidence of fatty deposits or calcification. The CT HU measurements are 17 HU pre-contrast, 21 HU at 0.5 minute, 32 HU at 1 minute, 41 HU at 1.5 minutes, 44 HU at 2 minutes, 51 HU at 4 minutes, 57 HU at 5 minutes, and 64 HU at 15 minutes. D. Hematoxylin and eosin (H&E) staining showes that the tumor was composed predominantly of spindle cells, adipose tissue, and blood vessels. In addition, normal-looking pulmonary alveoli and bronchi are seen inside the tumor (× 40). E. Spindle cells has elongated nuclei with inconspicuous nucleoli and are arranged in short fascicles in a collagenous background (H&E staining, original magnification × 200).

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Unusual CT Findings of Pulmonary Hamartoma

the iceberg’ appearance, on contrast-enhanced CT (Fig. 2). Dy-

Most pulmonary hamartomas are located peripherally in

namic contrast-enhanced CT demonstrated a heterogeneous,

lungs, and only 1–19.5% are located endobronchially (2). Pa-

persistently enhancing mass (Fig. 3). The CT Hounsfield unit

tients with endobronchial hamartoma can have respiratory com-

(HU) measurements were: 17 HU pre-contrast, 21 HU at 0.5

plaints (7). Our patient had a mass containing mostly extrabron-

minute, 32 HU at 1 minute, 41 HU at 1.5 minutes, 44 HU at 2

chial components with small endobronchial components, thus

minutes, 51 HU at 4 minutes, and 64 HU at 15 minutes. There-

exhibiting the ‘tip of the iceberg’ sign on CT images, which has

fore, the net enhancement of the mass was 47 HU. Positron emis-

not been previously described for fibroblastic hamartoma.

sion tomography and magnetic resonance imaging were not per-

Hamartomas that contain calcifications or fatty deposits can

formed. At this time, the differential diagnosis was inflammatory

be diagnosed by CT in 62% of cases (8). In a report of 11 ham-

myofibroblastic tumor or carcinoid tumor, because of the rela-

artomas (mean diameter, 1.5 cm; range, 1–3 cm), all masses ex-

tionship between the mass and the airway and its enhancement

hibited thick capsular and septal enhancement and persistent

pattern.

enhancement without washout (4). However, our patient had a

Percutaneous needle aspiration biopsy was not performed be-

relatively large mass (diameter, 3.8 cm) without evidence of cal-

cause the mass was relatively large and symptomatic and be-

cification or fatty deposits. Furthermore, although persistent en-

cause this technique has a low negative predictive value (about

hancement was observed on dynamic CT, net enhancement was

80%) (5). The mass was excised by right lower lobectomy via vid-

relatively high (47 HU). These abnormal findings prevented our

eo-assisted thoracoscopic surgery. The gross pathologic speci-

making a diagnosis by CT.

men thereby obtained appeared as an ill-defined, white, solid en-

According to a previous study, malignant nodules generally

dobronchial mass measuring 3.0 × 2.5 cm with exophytic growth.

present a net enhancement of ≥ 25 HU and a washout of 5–31

Hematoxylin and eosin staining revealed that the tumor was

HU. Also, benign nodules are characterized by one of the follow-

composed of mostly of spindle cells, adipose tissue, blood vessels,

ing: a net enhancement of < 25 HU, a net enhancement of ≥ 25

and alveoli (Figs. 4, 5). Immunohistochemistry showed that the

HU in combination with persistent enhancement, or a net en-

spindle cells were negative for S-100 protein, desmin, and smooth

hancement of ≥ 25 HU in combination with a washout of > 31

muscle actin, so they were thus identified as fibroblasts. Angio-

HU (9). Considering that the mass showed a net enhancement

myolipoma was considered because the tumor contained spindle

of 47 HU without washout, dynamic contrast-enhanced CT

cells, blood vessels, and adipose tissue, but negative immunos-

could have been useful for identifying a benign nodule in our

taining for HMB45 enabled us to exclude a diagnosis of angio-

case. We considered that the fibrous stroma of the tumor may

myolipoma or other clear cell tumors. Accordingly, a diagnosis of

have contributed to the persistent enhancement observed in our

pulmonary hamartoma with a predominant fibroblast compo-

case, and the delayed contrast enhancement might have been

nent was made. Five months after surgical resection, the patient

the result of contrast redistribution. Typically, after wash-in of a

was well and the condition had not recurred.

well-vascularized tumor cell zone during the early phase, contrast medium moves into fibrous stroma, which has scant blood

DISCUSSION Pulmonary hamartomas contain disorganized mixtures of various connective and epithelial tissues normally found in lung

supply, in the late phase, where it remains for a considerable time (4). Thus, it seems that the persistent enhancement pattern observed for many benign nodules is related to the amount and degree of fibrosis tissue (4).

(6). Hamartomas are divided into subtypes based on their main

We present the CT findings of pulmonary hamartoma with a

component; chondromatous hamartoma is the most common

predominantly fibroblastic component in a 20-year-old male.

(2). In our case, fibroblasts and fibrous stroma predominated,

Awareness of its imaging features, which include persistent en-

and thus, the mass was of the fibroblastic subtype. To the best of

hancement and ‘the tip of the iceberg sign’ on CT images, may

our knowledge, previous publication has reported the radiologic

substantially aid in the future diagnosis of this disease.

findings in cases of fibroblastic hamartoma.

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Seungbaek Hong, et al

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비전형적 폐과오종의 역동성 전산화단층촬영 소견과 그 병리학적 연관성: 증례 보고 홍승백1 · 정연주1 · 이지원1 · 김영대2 · 안효영2 · 이창훈3 · 김아롱3 · 이지원1* 저자들은 드문 병리학적 결과의 비전형적인 폐과오종을 갖는 20세 남자 환자의 역동성 조영증강 전산화단층촬영 소견을 보고하고자 한다. 전산화단층촬영에서 3.4 cm 크기의 ‘빙산의 일각’ 소견(‘tip of the ice berg’ sign)을 보이는 소엽성 종괴 가 우하엽 후기저분절의 중간 크기의 기관지에서 관찰되었다. 역동성 조영증강 전산화단층촬영에서 종괴의 밀도는 조영 증강 전에는 17 Hounsfield unit (이하 HU)이었고 조영증강 후 1분에 32 HU, 2분에 44 HU, 4분에 51 HU, 15분에 약 64 HU로, 지속적이며 비균질적인 조영증강을 보였다. 폐엽절제술을 시행하였고 병리 소견상 종괴는 두드러진 섬유모세포 성분을 가진 폐과오종으로 판명되었다. 부산대학교병원 의생명연구원 1영상의학과, 2흉부심혈관외과, 3병리과

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