Histologically most cases of lung cancer are adenocarcinoma, squamous cell carcinoma, large cell undifferentiated carcinoma, and small cell carcinoma.

If carcinoid and atypical carcinoid tumors are added to the above-mentioned histopathologic types, 99% of all primary lung neoplasms are accounted for.

In addition to carcinoid tumors, this chapter will focus on benign lung tumors, as well as a variety of nonbronchogenic primary pulmonary malignancies.

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  Classification of these neoplasms is problematic because of disagreement regarding the histogenesis of these varied tumors.

  
  
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  It is easiest to just discuss these neoplasms individually.

Most common benign lung neoplasm

Arrigoni and colleagues reported on 130 benign lung tumors from Mayo Clinic and found that 100 (76.9%) were hamartomas ( Table 33-1 ).

Pathology: These tumors are derived from peribronchial mesenchyme and are composed mostly of cartilage, connective tissue, fat, smooth muscle, and respiratory epithelium ( Fig. 33-1 ).

Hamartoma. It is well demarcated from the surrounding lung. Note the variegated white and yellow appearance which corresponds to the cartilage and fat.

Clinical presentation: Most are asymptomatic and account for 7% to 14% of pulmonary coin lesions.

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  In a review of 215 patients with hamartomas, Gjevre and associates found only 3% were symptomatic.

  
  
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  Commonly occur between the ages of 40 and 70 years, with a 2:1 to 4:1 male-to-female ratio.

Radiology: often solitary and can occur in any part of the lung but are more common in the periphery

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  The tumors measure from 1 to 7 cm (average 2 cm) in diameter.

  
  
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  A characteristic popcorn pattern of calcification may be present on computed tomography (CT) scan in up to 30% of cases, but some authors report a much lower incidence of calcification.

  
  
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  CT may also demonstrate fat within the lesion. Siegelman and colleagues reported fat in 50% of hamartomas ( Fig. 33-2 ).

  
  
  
  
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    The presence of fat density by high-resolution CT in a peripheral solitary lesion is strong presumptive evidence for a benign hamartoma.

  
  

  
  

  
  

  

  
  

  
  

  Computed tomography scan showing a 1-cm pulmonary nodule with a central fat density ( arrow ). This lesion has an appearance consistent with a hamartoma.

  
  

Pathology: Malignant transformation is rare.

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  Growth is slow.

  
  
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  Needle biopsy may be diagnostic.

  
  
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  This may be useful after CT studies when the diagnosis of hamartoma is still in doubt and the patient is poor risk for surgical intervention.

Treatment

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  Excision should be considered if the diagnosis is in doubt.

  
  
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  Small (<2 cm) hamartomas can be observed.

  
  
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  Hamartomas larger than 2.5 cm should be considered for excision.

  
  
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  Video-assisted thoracoscopic wedge resection is the preferred treatment.

  
  
  
  
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    Segmentectomy or lobectomy may be required, and pneumonectomy should be avoided.

  
  
  
  
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  Recurrence is highly unlikely.

Numerous synonyms: histiocytoma, plasma cell granuloma, plasmacytoma, xanthoma, xanthogranuloma, xanthofibroma, and inflammatory myofibroblastic tumor.

Pathology: Classically considered a non-neoplastic process characterized by unregulated growth of inflammatory cells.

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  Historically, cause was unknown but thought to represent an exaggerated tissue response to injury.

  
  
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  Now thought to be of neoplastic origin with evidence of rearrangement of the anaplastic lymphoma kinase gene on chromosome 2p23.

Presentation: The true incidence is unknown; however, in 56,400 general thoracic surgical procedures performed at Mayo Clinic between 1946 and 1993, 23 patients (0.04%) had resection of inflammatory pseudotumors.

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  Median age 47 years (range, 5 to 77 years).

  
  
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  They are the most common benign lung tumor in children.

  
  
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  Presentation is usually with symptoms: cough, weight loss, fever, fatigue.

Radiology: usually appear as well-defined solitary parenchymal masses 0.5 to 36 cm in diameter; the most common size is 1 cm to 6 cm.

Pathology: Grossly they consist of multilobular or bosselated tumor with a rubbery surface. They commonly have a white shiny appearance due to the large amount of fibrous tissue present; however, as the number of histiocytes or xanthomatous cells increase, their color becomes more yellow due to lipid accumulation ( Fig. 33-3 ).

Inflammatory pseudotumor. Note the sharp demarcation from the surrounding lung. The presence of xanthoma cells imparts a yellow color, plasma cells and lymphocytes a tan color, and fibrous connective tissue a white color.

Treatment is complete resection to avoid local recurrence.

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  In the Mayo Clinic series, complete resection was accomplished in 18 (78%) patients. Resection required pneumonectomy in six patients, bilobectomy in one, lobectomy in six, segmentectomy in one, wedge resection in seven, and chest wall resection in two.

  
  
  
  
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    Two patients with positive margins underwent re-resection, and two have been observed without evidence of tumor growth.

    
    
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    The 5-, 8-, and 10-year survival rates were 91.3%, 91.3%, and 77.7% respectively.

  
  

Presentation: Rare, with only two found out of 130 benign lung tumors in the Mayo Clinic series.

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  Most are endobronchial and cause obstruction.

Radiology: Because of their fatty composition, CT may strongly suggest the diagnosis of endobronchial lipoma.

Treatment: Use bronchoscopic removal whenever possible.

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  Muraoka and associates reported on 64 cases with surgical procedures including pneumonectomy in four patients, lobectomy in 24, bilobectomy in eight, bronchotomy in four, bronchoscopic removal with Nd:YAG laser in 17, cautery in five, and a combination of laser and cautery in five.

  
  
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  Reasons for surgical resection include

  
  
  
  
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    Difficulty in obtaining a definitive diagnosis and the existence of a possible complicated malignant tumor

    
    
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    Peripheral destruction of the lung secondary to long-standing atelectasis or pneumonia

    
    
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    Extrabronchial growth or the existence of subpleural lipomatous disease

    
    
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    Technical difficulties encountered during the bronchoscopic procedure

  
  

Presentation:

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  Account for 1.5% to 2% of benign lung neoplasms

  
  
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  Most common in young and middle-aged women

  
  
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  Location split almost evenly between lung parenchyma and tracheobronchial

  
  
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  Peripheral lung parenchymal leiomyoma are often asymptomatic while tracheobronchial leiomyoma may cause pulmonary obstruction.

Radiology: On CT, there are no distinguishing features from other pulmonary nodules.

Pathology: Grossly, they resemble smooth muscle tumors ( Fig. 33-4 ).

Benign pulmonary leiomyoma. The nodule is lobulated with a typical pale white smooth muscle appearance.

Treatment

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  Endobronchial leiomyoma without destroyed distal lung parenchyma may be treated with endobronchial resection with or without the use of Nd:YAG laser.

  
  
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  Surgical resection is the treatment of choice for peripheral leiomyoma and those endobronchial leiomyoma with destroyed distal lung tissue.

Benign metastasizing leiomyoma

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  Term used for multiple (occasionally single) well-differentiated pulmonary smooth muscle nodules found almost exclusively in women, many of whom have a history of uterine leiomyoma.

  
  
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  Pathology: very bland cytologic appearance, with minimal mitosis or necrosis very similar to uterine leiomyomas.

  
  
  
  
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    Controversial term because they have hematogenously spread from benign uterine leiomyoma; this contradicts their “benign” designation.

    
    
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    Kayser and colleagues compared benign metastasizing leiomyomas with uterine leiomyomas using a variety of markers such as estrogen receptor (ER) and progesterone receptor (PR) receptors and Ki-67. They concluded that benign metastasizing leiomyomas are in reality slow-growing uterine leiomyosarcomas.

    
    
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    Takemura and colleagues believe that benign metastasizing leiomyomas could be due to multicentric benign leiomyomatous growths instead of actual metastases.

  
  
  
  
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  Treatment

  
  
  
  
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    Pulmonary resection can be considered when feasible and for establishment of diagnosis.

    
    
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    These tumors can regress following oophorectomy.

    
    
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    Because these tumors are ER- and PR-receptor positive, they may respond favorably to hormonal therapy.

  
  

Sclerosing hemangioma

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  Presentation: Sugio and colleagues reported sclerosing hemangioma as the 2nd most common benign lung neoplasm following hamartoma.

  
  
  
  
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    Eighty percent occur in women.

    
    
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    Most are asymptomatic.

  
  
  
  
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  Radiology: they appear as a solitary, circumscribed, homogeneous mass that occasionally is calcified.

  
  
  
  
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    They range in size from 0.4 cm to 8.0 cm, with an average of 2.8 cm.

  
  
  
  
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  Pathology: Four major histologic patterns exist: solid, papillary, sclerotic, and hemorrhagic. Most of these neoplasms exhibit combinations of these patterns.

  
  
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  Treatment: Surgical resection is the procedure of choice.

  
  
  
  
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    Miyagawa-Hayashino and colleagues have reported on 4 patients with sclerosing hemangioma and lymph node metastases.

    
    
    
    
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      Lymph node metastases were described as peribronchial, regional, and hilar.

      
      
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      Despite the presence of lymph node metastases, these authors still consider sclerosing hemangiomas to be benign.

      
      
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      Because of the possibility of lymph node metastases, a regional and hilar lymph node dissection should be done in addition to surgical resection of the sclerosing hemangioma.

    
    

  
  
  
  
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  Prognosis is excellent, and prognosis did not appear to be affected by the presence of lymph node metastases.

Cavernous hemangioma

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  Presentation: Extremely rare, occurring in all age groups

  
  
  
  
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    Shields and Robinson consider these to be pulmonary arteriovenous malformations (AVMs).

    
    
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    May occur in the tracheobronchial tree or in the peripheral lung parenchyma

    
    
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    Presentation may be asymptomatic or include hemoptysis, respiratory distress, or congestive heart failure.

  
  
  
  
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  Treatment

  
  
  
  
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    Endobronchial lesions are managed by Nd:YAG laser.

    
    
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    Parenchymal AVMs can be embolized with metal coils and occasionally require surgical excision.

  
  

Synonyms: mucous gland cystadenoma, adenomatous polyp, and adenomas of mucous gland type

Presentation: Rare neoplasm that occurs in both children and adults, and is more common in women.

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  Arises in the bronchus and derived from bronchial mucus glands

  
  
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  Because of their bronchial location, patients often have symptoms secondary to obstruction or hemorrhage: cough, fever, hemoptysis, recurrent pneumonia.

Pathology: Grossly the tumors are soft, spherical, polypoid endobronchial nodules that are usually smaller than 2 cm in diameter but may range up to 7 cm.

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  They are more common lower or middle lobe lobar or segmental bronchi.

  
  
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  The differential diagnosis includes low-grade mucoepidermoid carcinoma.

  
  
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  Distinguishing between the two types may be difficult with small biopsies. The lack of cytologic atypia, mitoses, and necrosis aids in differentiation.

Treatment

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  Endobronchial resection with or without the use of Nd:YAG laser or cryotherapy if there is no distal lung destruction

  
  
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  Surgical resection is the treatment of choice for these neoplasms if there is destroyed distal lung parenchyma or there are contraindications to endoscopic resection

Prognosis: excellent.

Benign tumors composed of hyaline cartilage, which may be parenchymal or involve the cartilaginous airways.

Presentation:

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  Endobronchial chondromas are often associated with obstructive symptoms, are more common in men, and may be treated by endobronchial removal or surgical resection.

  
  
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  Although parenchymal chondromas are frequently asymptomatic, they are more common in women and may be associated with Carney’s triad. In fact, the presence of a pulmonary chondroma in a young woman should lead to consideration of this triad, which includes

  
  
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  Chondroma of the lung single or multiple

  
  
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  Gastrointestinal stromal tumor

  
  
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  Extra-adrenal paraganglioma

Treatment: repeated surgical resections of the respective tumors

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  Lung parenchymal–sparing resections are adequate for pulmonary chondromas.

Prognosis

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  For a single pulmonary chondroma, overall survival is excellent.

  
  
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  For patients with Carney’s triad, despite repeated resections, the development of recurrent neoplasms is common. Neoplasms that grow or cause symptoms should be resected. Carney’s triad is a chronic, persistent, indolent disease extending over a long period of follow-up. Sixteen percent of patients eventually die of the disease.

Atypical adenomatous hyperplasia (AAH) is of increasing interest because of its association with bronchoalveolar carcinoma (BAC).

Pathology: AAH is a focal lesion smaller than 5 mm in diameter due to proliferation of atypical bronchoalveolar cells lining centriacinar alveoli.

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  Autopsy studies have demonstrated AAH in 2% to 4% of cases.

Presentation: Demographic data are conflicting.

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  May be more common in women

  
  
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  May be more frequent in Japanese individuals

Radiology:

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  Most AAH is completely invisible; however, when visible, it may present on thin-section high-resolution CT as tiny foci of ground-glass opacification within the lung parenchyma.

  
  
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  These ground-glass features, however, are not specific to AAH.

Differential diagnosis is primarily with BAC.

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  Grossly, AAH is typically smaller than 5 mm in diameter and BAC is larger than 10 mm; however, size alone cannot reliably make the distinction between the two.

  
  
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  Pathology: cell population of AAH may be more heterogenous and BAC more monomorphic. Of the following histologic features, AAH rarely demonstrates more than one, whereas BAC exhibits three or more.

  
  
  
  
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    Marked cell stratification

    
    
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    High cell density, with marked overlapping of nuclei

    
    
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    Coarse nuclear chromatin and prominent nucleoli

    
    
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    True papillae or an obvious picket-fence growth pattern

    
    
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    Increase in columnar cell height in excess of those lining terminal bronchioles

  
  
  
  
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  BAC

  
  
  
  
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    There are little data on the appropriate treatment of AAH.

    
    
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    In most cases, treatment is determined by the associated lesions that may be present.

    
    
    
    
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      If a ground-glass opacity is resected and AAH is identified, then only a wedge resection with free margins is required.

      
      
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      Even for BAC, there is a growing consensus that sublobar resection may be adequate therapy.

    
    

  
  

Describe a group of slow-growing neoplasms, most of which arise from the bronchial glands

Three histologic types of tumors

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  Bronchial carcinoids

  
  
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  Adenoid cystic carcinoma

  
  
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  Mucoepidermoid carcinoma

The term bronchial adenoma is a misnomer because these tumors are usually low-grade malignancies and not benign neoplasms as the term adenoma implies.

The term bronchial adenoma should be avoided whenever possible.

History: First described by Otto Lubarsch in 1888 who identified multiple tumors in the distal ileum of two patients at autopsy.

Sigfried Oberndorfer in 1907 coined the term karzinoide to describe tumors with carcinoma-like features but a much more indolent behavior.

Pathology

Pulmonary carcinoids are malignant neuroendocrine tumors comprising 1% to 2% of all primary lung tumors and 85% of bronchial gland tumors.

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  Carcinoid tumors are part of the spectrum of malignant neuroendocrine tumors, which range from low-grade typical carcinoid tumors to intermediate-grade atypical carcinoid tumors to high-grade tumors, including large cell neuroendocrine carcinoma and small cell lung carcinoma.

  
  
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  Most pulmonary carcinoid tumors arise in major bronchi.

  
  
  
  
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    Ten percent in mainstem bronchi

    
    
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    Seventy-five percent in lobar bronchi

    
    
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    Fifteen percent in the lung periphery that is segmental bronchi and distal

  
  
  
  
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  Frequently have a large endobronchial component with a fleshy smooth polypoid mass protruding into the bronchial lumen ( Fig. 33-5 ). The cut surface may appear tan-yellow or red depending on the extent of vascularity.

  
  

  
  

  
  

  

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