The Adult Form of. Pulmonary Hamartoma. O.S. U. Series. A Reappraisal. Malvin Weinberger, M.D., Gerard S. Kakos, M.D., and James W. Kilman, M.D.

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1 The Adult Form of Pulmonary Hamartoma A Reappraisal Malvin Weinberger, M.D., Gerard S. Kakos, M.D., and James W. Kilman, M.D. ABSTRACT Pulmonary hamartoma is often an incidental, asymptomatic finding on routine chest roentgenogram. It has been considered a congenital malformation since the original description by Albrecht in 1908 and has been classified into two types, a small, fibrocartilaginous mass in adults, and a cystic lobar mass in infants. The adult type is an unusual finding in patients under the age of 20 years, and a review of the experience at one large hospital shows a preponderance in the fifth and sixth decades of life, as has been found in other reported series. Although many investigators consider the so-called adult pub monary hamartoma to be a late-appearing developmental anomaly or malformation, its histogenetic and behavioral characteristics are more similar to those of a benign acquired tumor. These factors suggest that it should be reclassified as such. T he adult form of hamartoma of the lung is an enigma. Its embryological origin, growth characteristics, and behavior have not been satisfactorily explained despite increased clinical recognition of its incidence. Recently, the unusual presentation and behavior of a hamartoma in a 12-year-old boy prompted us to review our experience at the Ohio State University Hospitals as well as to survey other reports in an effort to develop a better understanding of this lesion. O.S. U. Series We reviewed 29 patients with histologically proved adult-form hamartoma from a population whose age spanned 12 to 71 years with a mean of 58 years. There were 18 male patients and 11 female patients in the series. All the lesions but 1 were intrapulmonary and subpleural. The size ranged from 0.5 cm. to 7.0 cm. with an average diameter of 2.5 cm. Only 1 lesion was symptomatic; the remaining lesions were asymptomatic findings on routine chest roentgenograms. Resection was carried out in all patients and included 23 enucleations or subsegmental resections, 5 lobectomies, and 1 pneumonectomy; this last case will be reviewed. On gross examination, all the hamartomas were uniformly rubber-hard with a lobulated surface. The majority were easily demarcated from the surrounding pulmonary tissue. From the Divisions of Pediatric Surgery and Thoracic Surgery, Department of Surgery, Ohio State University Hospitals and Columbus Children's Hospital, Columbus, Ohio. Accepted for publication April 10, Address reprint requests to Dr. Kilman, Division of Thoracic Surgery, Ohio State University Hospitals, 410 W. 10th Ave., Columbus, Ohio VOL. 15, NO. 1, JANUARY,

2 WEINBERGER, KAKOS, AND KILMAN A FIG. 1. (A) Roentgenogram of the patient at the age of 9 years showing small peripheral mass in right upper lung field. (B) Roentgenogram three years later shows marked enlargement of the tumor mass and atelectasis of peripheral tissue. Note calcification in the mass in both films. B Microscopically they contained all components of bronchial tissue, but in differing proportion. Most prominent were areas of fibrosis and fibrocartilage and numerous cleftlike spaces lined by columnar or cuboidal epithelium. One large lesion had a small bronchus leading to it. CA$E KEVIEW A 12-year-old boy was first seen in 1966 at the age of 9 years, at which time a routine chest roentgenogram (Fig. 1A) showed a 2 cm. lobulated, calcified mass in the right upper lobe. Physical examination was normal, and no progression in the size of the mass was seen over one year. The clinical impression was that the lesion was a granuloma. He was lost to followup for two years, and when he was seen again in 1969, repeat films (Fig. 1B) demonstrated an increase in size to 7 cm. At thoracotomy the mass was found to encircle the hilar vasculature and bronchi, and pneumonectomy was required for removal of the lesion (Fig. 2). Comment. The excessive growth of this mass over a 2-year period raised the specter of malignancy. The location precluded a more limited resection. Improved follow-up with an earlier thoracotomy would have allowed a lesser procedure to be done for adequate removal without the loss of additional functional tissue. Comment The concept of hamartoma is traceable to Albrecht, who first described these tumorlike, nonneoplastic malformations as an abnormal mixture or 68 THE ANNALS OF THORACIC SURGERY

3 Adult Form of Hamartoma FIG. 2. Photomicrograph of a section of the excised tumor. (H&E; X88.) arrangement of tissues indigenous to a part with an excess of one or more components. Two distinct pulmonary lesions have been labeled collectively as hamartomas, a small, fibrocartilaginous solid mass in adults, and a cystic lobar mass seen most often in the neonatal period. Because of this diversity in structure, many workers, perhaps erroneously, have classified pulmonary hamartoma into infantile and adult types. The infantile form is rare and includes congenital lung cysts and cystic adenomatoid malformations of the lung. Respiratory distress in the newborn period with progressive cough, wheezing, and cyanosis are the usual presenting symptoms. Even when discovered in older children, the lesion is associated with respiratory symptoms. Recent reports of Izzo and Rickham 171 and Moncreiff and his associates [l 13 have adequately reviewed experiences with this anomaly. Clinically and histologically it differs significantly from the more common adult form of hamartoma. We have treated 4 children with infantile hamartoma at the Columbus Children s Hospital since The so-called adult type has included those lesions variously referred to as chondrohamartoma [3], chondroadenoma [ 13, adenolipofibroosteochondroma [31, lipochondroadenoma [4], bronchoma [Z], and mixed tumors of VOL. 15, NO. 1, JANUARY,

4 WEINBERGER, KAKOS, AND KILMAN the lung [5]. They are usually asymptomatic and are discovered by way of routine chest roentgenograms. If followed over a period of time, they evidence little if any growth. Malignant alteration has rarely been reported [6]. The true incidence of adult hamartoma is unknown since the majority of these lesions are asymptomatic. In one series of 8,000 postmortem examinations reported from the Mayo Clinic, hamartoma was an incidental finding in 0.25% [91. In another study [8], hamartoma accounted for 8.0% of all solitary coin lesions on chest roentgenograms, ranking behind primary carcinoma, granuloma, and tuberculoma. No predilection for either lung or a particular lobe exists. Most series report a male predominance of 2: 1, and the usual age of discovery is in the fifth or sixth decade, leading to confusion with primary or metastatic malignancies. The adult hamartoma occurs predominantly within the lung parenchyma, with 10% arising there and remaining endobronchial. Infrequently, an extralobar location has been noted with a pedicle attachment to the bronchus or pulmonary ligament [ 131. This common peripheral location accounts for the lack of symptoms unless adjacent tissue is compressed with subsequent atelectasis and pneumonitis. Criteria for a differential radiological diagnosis have been described in an extensive review by Bateson and Abbott [3]. In essence, the roentgenographic manifestations of hamartoma include a sharply defined parenchymal tumor, often with lobulated margins, occurring in a subpleural location. These lesions are usually less than 3 cm. in diameter, and irregular patches of calcification with a popcorn appearance and areas of lesser density near the periphery due to collections of fat may be seen, but need not be present. The first report discussing any growth in size was that of Weisel, Glicklich, and Landis [15] in 1955, who called attention to a slow increase in the size of the hamartoma in 10 patients over a three-month to five-year period, i.e., an increase of 0.5 cm. in diameter per year. A single report [14] in 1968 documented the growth of a hamartoma from 1.0 to 2.6 cm. over an eighteen-month period, and this was considered extraordinary by the authors. The origin of hamartoma and the stimulus for its growth are obscure. Most workers accept the premise that the lesion is a malformation and not a neoplasm, and that it emanates from embryonic connective tissue cells of the bronchial walls, which retain the potential for new growth at any age. This explanation holds for the infantile type but is difficult to reconcile with the characteristics of the adult lesion. We would expect confirmatory evidence for the theory to come from reports of growth coinciding with the growth spurts in human development, i.e., during childhood and adolescence; or if not coinciding with growth spurts, the lesion at least should grow at a parallel rate with the host pulmonary tissue. Morison [12] in discussing hamartoma has stated, They may show periods of growth independent of the body, but they all tend to grow with the part affected and, unless neoplastic potentialities appear, usually cease to grow when its growth 70 THE ANNALS OF THORACIC SURGERY

5 Adult Form of Hamartoma stops. As is documented in our series and by others, such is not the case. At present, numerous routine chest roentgenograms have been taken in youths of military age and younger, and yet no increased incidence of hamartoma in this age group has been noted. We could find but 6 additional case reports of the adult form of pulmonary hamartoma in people under the age of 20 years. For a mass lesion that would be considered a growth-related entity to appear primarily in the fifth and sixth decades seems inconsistent with the theory. Another explanation is that hamartoma arises as a hyperplastic response to inflammation. The commonness of pulmonary infections and rarity of hamartoma make this an unlikely conclusion, however. Finally, a third theory, and perhaps the most plausible, is that of Willis [16], who believes the lesion is not a hamartoma,at all, but a benign acquired tumor. Willis reserves the term hamartoma for lesions showing clear evidence of an underlying developmental anomaly, either present at birth or manifested by overgrowth during normal tissue maturation. Among the lesions he would accept as meeting the definition of hamartoma are benign angioma, skeletal exostosis, and enchondroma. In lung tissue, Willis considers that only the infantile hamartoma has characteristics which qualify it as a true hamartomatous lesion. Moller [lo] in 1933 showed that the adult lesion is a mixed tumor of the bronchial wall in which epithelial proliferation is accompanied by underlying mesenchymal tissue proliferation. Bateson and Abbott [3] analyzed the similarity in structure and development of parenchymal and endobronchial adult hamartomas and ascribed any differences solely to the site of origin in either major or peripheral bronchi. We are of the opinion that the so-called adult hamartoma is not a hamartoma at all, but, as Willis proposed, a benign acquired tumor. Clinically and histologically it differs significantly from the infantile hamartoma and behaves as an acquired benign tumor. Unfortunately, the popular application of this term and common understanding of what it means are thoroughly ingrained in the medical terminology. A change analogous to the past reclassification of fibroadenomas of the breast seems in order. Conclusions Adult-type pulmonary hamartoma is often an incidental, asymptomatic finding on routine chest roentgenogram. It is an unusual finding under the age of 20 years and appears preponderantly in the fifth and sixth decades of life. Although many workers consider adult hamartoma to be a late-appearing developmental anomaly or malformation, its histogenetic and behavioral characteristics are more similar to those of a benign acquired tumor. These factors strongly suggest that it should be reclassified as such. VOL. 15, NO. I, JANUARY,

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