Leiomyoma and \201 broleiomyoma These are extremely rare tumors and usually occur in mid- dle aged women. Pulmonary leiomyomas resemble those encountered in other sites. They are w ell circumscribed. Angiomyolipoma These are also extremely rare benign tumors which are hamartomas and compose d of a mixture of blood vessels, smooth muscle and fat. Although most commonly found in the kidney they have rarely been reported in the lung. Speci \201 c types of benign parenchymal lung tumor Soft (connective) tissue tumors Chondr oid hamartoma and related lesions These tumors, although relatively uncommon, are, in terms of benign lung tumors, the commonest type and account for about 8% of coin lesions seen on CXR. They are commonest in late middle age, show a male preponderance, most are parenchyma l and consequently asymptomatic but about 10% are endobronchial and cause endobronchial sym ptoms. Massive haemoptysis has been described. They comprise a mixture of various connectiv e tissues (fat, carti- lage, smooth muscle) and epithelial tissue components, but there is debate as to whether these lesions are truly ham- artomas or are true neoplasms. The term m esenchymoma has been proposed and it is now recognized that pulmonary lipomas, chondromas a nd \201 bromas may be related neo- plasms. These monotypic examples are, however much les s common than the heterogeneous \200\230chondroid hamartoma \200\231. The connective tissu e components may calcify, giving the characteristic \200\230pop-corn \200\231 pattern of c alci \201 cation in some lesions on the chest radiograph. Fig. 13.9.3 This is an endobronchial chondroid hamartoma. The cartilage plates and seromuco us glands of the native bronchus are seen below, the lesion comprising connective and adipo se tissue and cartilage, which has ossi \201 ed and has a substantial component of bone ma rrow (top right). (See Plate 11.) In \202 ammatory myo \201 broblastic tumor This rare pulmonary lesion is a member of the rare heterogeneous group of so-called in \202 ammatory pseudo- tumors. It has many synonym s and has subsumed a number of previous \200\230entities \200\231 such as plasma cell gran u- loma and \201 brous histiocytoma. It occurs most often in patients aged under 40 years and shows an equal gender distribution. Most lesions present as localized pulmonary masses which may mimic carcinoma radiologically. Signs and symptoms are dependent on the localiza tion of the lesion. Rarer endo-bronchial lesions may cause cough, wheeze and hae- moptysis. Peripheral lesions give fewer symptoms unless the chest wall is involved. Fig. 13.9.2 CT image of a calci \201 ed chondroid hamartoma. These lesions show a heterogeneous mixture of spindles cells, macrophages and variable in \201 ltrates of chronic in \202 am- matory cells. Giant cells may be seen. Atypia is rare but the tendency to occasionally invade locally, recur after excision and even rarely metas tasise has led some to consider this lesion a low grade malignancy. The pathological features of pulmonary hamartomas are the same wherever they arise, be it i n the lung parenchyma or as endobronchial growths. They are usually 1 \200\2233 cm in size but can grow up to 9 cm. Those arising in a parenchy- R MILROY & K KERR 312 presentation is wide (10 \200\22360 years),with a median age at 40. Half of the patients ar e asymptomatic. The remain- der complain of cough, and of breathlessness. Typical radiologi c \201 ndings are the presence of multiple bilateral, sometimes calci \201 ed small nodu les of 1 \200\2232 cm diameter, though solitary masses may occur. Typically this condition is misinterpreted as metastatic disease or old granuloma- tous in \202 ammation. Histologi cally the tumor shows cords and nests of epithe- lioid endothelial cells set in a rather my xoid stroma. This tumor may also occur in the pleura. The multiple tumors slowly enlarge ov er a period of years and patients die of respiratory failure. Other vascular tumors Haemangioma and lymphangioma are exceedingly rare in the lung. They r esemble similar tumors elsewhere in the body and form well circumscribed lesions. They tend to be intrapulmonary but may occur endobronchially. Such a case causing haemoptysis has be en described. Fig. 13.9.4 Bronchial lipoma showing accumulations of adipose tissue deep to the respirator y mucosa. Clear cell tumor This benign lung tumor has also been named the \200\230sugar tumor \200 \231. Less than \201 fty cases have been reported in the world literature. They tend to o ccur in middle aged patients who are usually asymptomatic and the tumor is an incidental so litary \201 nding. This is probably a tumor of perivascular epithelioid cells (so-called PEC cells) and the most important differential diagnosis would be with metastatic renal cel l carcinoma since the lesion comprises large but banal looking cells with clear cytoplasm c ontaining abundant glycogen. These tumors are quite vascular. The benign pulmonary tumor wi ll not express cytokeratins but will express HMB45. The tumor is usually peripheral and res ection is generally curative. Neural tumors These include nerve sheath tumors, and granular cell tumors. They are all ext remely rare occurences in the lung. Nerve sheath tumors comprise both neuro \201 bromas an d neurilemmomas which are identical to their counterparts elsewhere. These tumors are somet imes associated with neuro \201 bromatosis. They may be parenchymal but have also been fou nd in the airways and visible on bronchoscopy. Granular cells tumors are more often endobro nchial and discussed later. Parenchymal epithelial tumors Sclerosing pneumocytoma (sclerosing haemangioma) Despite the original belief that this was a vascular tumor, hence the term \200\230haemangioma \200 \231, it now clear that this is an epithelial tumor showing pneumocyte differentiation. Vascular tumors Epithilioid haemangioendothelioma This is a low grade but potentially malig nant endothelial tumor, 80% of which occur in women. Age range at Table 13.9.1 Benign tumors and tumor-like conditions of the lung Parenchymal tumors Epithelial neoplasms Soft tissue and other neoplasms Non-neoplastic conditions Alveolar adenoma Papillary adenoma Mucinous cystadenoma Sclerosing haemangioma (pneumocytom a) Thymoma Pleomorphic adenoma Hamartoma Chondroma Lipoma Fibroma Leiomyoma Clear cell (sugar) tumor Meningioma In \202 a mmatory myo \201 broblastic tumor Granular cell tumor Epithelioid haemangioendothelioma Amyloid tumor Hyalinising granuloma Malakoplakia Endometriosis A-V malformation Lymphoproli ferative disorders Endobronchial tumors Epithelial neoplasms Soft tissue and other neoplasms Non-neoplastic conditions Papillomas Squamous papilloma Glandular papilloma Mixed papilloma Bronchial gland adenomas Mucous gland adenomas Oncocytoma Pleomorphic adenoma Hamartoma Chondroma Lipoma Granular cell tumor Fibroin \202 ammatory polyps Amyloid tumor Foreign body Bacillary angiomatosis CHAPTER 13.9 Benign lung tumors 313 These tumors are commonest in middle age and com- moner in women. These lesions are much co mmoner in East Asia, especially Japan. The are usually asymptomatic, but cough, pain and ha emoptysis may occur. Pathologically the tumors tend to compress adjacent nor- mal lung pare nchyma and most measure under 3cm, though lesions up to 8cm are described. Most are solitar y lesions though around 4% are multiple. The two basic histological features of a sclerosin g pneumocytoma are the presence of sclerosis and papillary epithelial proliferation but the y may show a very wide range of features including alveolar-like spaces and a dual populati on of larger pale cells and smaller \200\230stromal \200\231 cells. Haemorrage and heamosi derin are com- monly present. Immunohistochemistry for cytokeratins and TTF1 are key to the histologic diagnosis. Wegener \200\231s granulomatosis, nodular sarcoidosis and infec- tious granulomatous masses enter the differential diagnosis of benign lung tumors but are discussed elsewhere. Other benign non-neoplastic conditions which may mimic neoplasia include rounded atelectasis (see above), seques- tered pulmonary segments and organizing pneumonia. Also included in this c ategory are amyloid tumor, hyalinis- ing granulomas, malakoplakia, thoracic (usually pleura l) endometriosis, AV malformations and some unusual lym- phoproliferative conditions, which are brie \202 y discussed. Amyloid tumor Amyloid tumor in the lung can occur in isolation or as part of systemic amylo idosis. Nodules may be solitary or multiple and can occur endobronchially, when the patient may be symptom- atic. Most patients are middle aged. Localized pulmonary amyloid tumors co mprise masses of eosinophilic amorphous material which elicits a foreign- body type giant c ell reaction. Calci \201 cation or even ossi \201 ca- tion have been described. A minorit y of these patients will have a lymphoproliferative disorder associated with the amyloid an d screening for serum paraproteins may be appropriate. Mucinous cystadenoma These are extremely rare tumors, lined by columnar mucin-secreting epi thelium, enveloping a uniloculate space \201 lled with mucin. They tend to occur in elder ly patients. Cases with borderline malignant histological features have been described. De \201 nitive diagnosis requires surgical exci- sion, which is curative. Thoracic endometriosis This condition is rare and usually affects the pleura or sub pleural lung tissue but occasionally is purely intrapulmonary. Patients may have an incidental tum or \200\223like abnormality identi \201 ed on the CXR but catamenial pneumothorax and haem optysis have been reported. Alveolar adenoma These are well circumscribed tumors. All lobes have been reported to be in volved though there is a predeliction for the left lower lobe. They comprise micro- and mac rocystic spaces, a feature which may be apparent on CT scan, lined by alveolar pneumocytes, all embedded in a variably dense \201 - brous stroma. These lesions have been described up to 6cm in diameter and are usually asymptomatic incidental \201 ndings. Following surg ical resection there have been no reports of recurrence. Arterial venous malformation Developmental AV \201 stulae in the lungs have long been rec ognized and a signi \201 cant number of cases have been described in the world literature. They represent a vascu- lar hamartoma with abnormal communications between pulmonary arter ies and veins. These lesions may be single or multiple and often increase in size with age. Although the abnormality develops in fetal life, patients usually present in middle age wi th haemoptysis or features of chronic hypoxia if there is an appreciable arterial venous sh unt. These vascular malformations tend to occur in the periphery of the lung and are not in frequently multiple. The treatment of choice is balloon occlusion or embolisa- tion followi ng angiography. Papillary adenoma This is an extremely uncommon parenchymal neoplasm, predominantly found i n males of widely ranging age who are asymptomatic. Tumors are well de \201 ned encapsulat ed masses showing a compact growth of true papillae lined by bland epithelial cells which a re a mixture of Clara cells, type 2 pneumocytes and even ciliated cells. Surgical exci- sio n is curative. Intrapulmonary thymoma Primary thymoma has been described both in the lung and pleura and i s thought to arise from thymic rests in these tissues. Typically patients with a pulmonary thymoma will present with an asymptomatic peripheral pulmonary nod- ule. Such ectopic thymo mas are identical to those that arise in the thymus but generally are not so obviously sur- rounded by a capsule. Pulmonary thymomas are usually benign, slowly growing and are cured by complete surgical resection. As with mediastinal lesions, malignant forms do occur. Pleu ral thymoma has also been described and this presents as an asymptomatic pleural nodule or thickening on chest imaging. Patients with pleural thymoma may also present with symptoms s uch as chest pain, fever, cough and weight loss. There is a case report of a patient who pr esented with an intra pulmonary thymoma who had myasthenia gravis. Angiofollicular lymph node hyperplasia (Castleman \200\231s Disease) Although angiofolicula r lymph node hyperplasia usually involves mediastinal lymph nodes, it has been reported in the lung and the pleura, and the chest wall. Two speci \201 c histological sub types have been described \200\223 hyaline-vascular and plasma cell. The hyaline-vascular pattern is much com- moner and often presents as a random \201 nding on CXR. However, patients may p resent with symptoms due to pressure effects. This tends to be a more localized form of dis ease. The plasma cell pattern is more often multi- centric. It is associated with systemic features, lymphade- nopathy and hepatosplenomegaly and has an aggressive course. In contras t the solitary form of disease is benign and usually cured by surgery. Benign endobronchial tumors Endobronchial tumors usually present with \200\230bronchial \200\231 symptoms such as cough, haemoptysis, breathlessness, wheeze and stridor. Patients may be misdiagnosed as Parenchymal tumor-like conditions There is a wide range of benign lesions which present as masses mimicking neoplasms, yet are non-neoplastic. Many of these lesions, such as rheumato id nodules, localized