Fine needle aspiration diagnosis of pulmonary hamartoma.

Hamartomas are composed of an abnormal admixture of normal constituents of the organ in which they are found.[1] Pulmonary hamartoma (PH) although rare, is the most common benign tumor of the lung. It usually presents as a coin-like lesion on conventional radiography. Fine needle aspiration cytology (FNAC) helps in differentiating it from other lesions like carcinomas, metastasis and granulomas.[2] The diagnosis of PH by FNAC is of considerable clinical importance as the technique can be used before any invasive procedure.

A 70-year-old female presented in Pulmonary Medicine OPD with complaints of pain chest for 3 months. Chest radiograph revealed opacity in the right middle lobe of the lung parenchyma. Computerized tomography (CT) showed a soft tissue mass measuring 3.3 × 3.2 cm with smooth walls in the anterior segment of the right middle lobe. The patient was subjected to CT-guided transthoracic FNAC with the suspected clinical and radiological diagnosis of malignancy.

Aspiration was performed using 22-G lumbar puncture needle attached to a disposable 20-ml syringe mounted on Cameco handle. Slides were prepared and residual material was put in formalin to be processed as cell block. Aspiration smears were stained with May-Grünwald-Giemsa (MGG) and hematoxylin and eosin (H and E) stains. Cell block sections were stained with H and E stain. FNA procedure was uneventful. The smears showed prominent chondroid material, fibromyxoid stroma and benign bronchiolar epithelial cells [Figure 1]. The chondroid material was dense homogenous and stained pale with H and E and bright magenta with MGG stain. Bronchiolar epithelial cells were present singly and in sheets closely associated with the chondroid material. These cells had abundant pale cytoplasm and no cytological atypia was seen. The fibromyxoid tissue was seen as fibrillary material with wispy edges and admixed spindle cells. No inflammatory cells or necrosis was seen. Cell block showed a fragment of benign cartilaginous component; however, no epithelial cells could be seen. In view of the above cytological findings on smears and cell block, the diagnosis of PH was rendered. The patient is on regular clinical follow-up and she remains well 2 years later.

Figure 1

FNA smear showing chondroid material and benign bronchiolar epithelial cells (MGG, ×400). Inset shows fibromyxoid stroma with benign spindle cells (H and E, ×400)

PH is a well-circumscribed lesion usually smaller than 4 cm in diameter. The lesions are more common in men and the average age of presentation is 5th to 6th decade. Because of its peripheral location, patients of PH are usually asymptomatic; however, patients with an endobronchial lesion usually present with wheezing or hemoptysis. On imaging, PH characteristically appears as sharply outlined round/oval lobulated solitary pulmonary nodule with varying patterns of calcification. Popcorn calcification if present is virtually diagnostic.[1]

Majority of PH are chondromatous (chondroid hamartoma) and the remaining are either vascular or have predominance of fibrous tissue or myxomatus tissue.[1] The chondroid hamartoma is of firm texture and the aspiration needle may be deflected or may bend when inserted into it. Firm to gelatinous material which is difficult to express onto the slide can provide a clue to the diagnosis.[2] Sometimes aspirate may be scanty because of the dense nature of the lesion.[3] In such cases the use of a wide gauge needle helps in obtaining adequate material.

The cytological smears consist of nonorganized epithelial and mesenchymal tissues. Epithelial cells consist of normal appearing bronchial cells and appear as sheets of small, uniform, cuboidal or columnar cells and bare nuclei. Mesenchymal tissue such as fat, smooth muscle, cartilage, fibrous tissue and occasionally bone can be seen. Mature cartilage is distinctive when present, but is seen in a minority of cases. Fibromyxoid stroma and chondroid material are common features seen in PH. Fibromyxoid stroma is identified as stromal material intermixed with spindled cells. Chondroid material is identified as dense, homogenous glassy or slightly refractile material with or without lacunae.[4-6] Chondroid material in the absence of other components can be misdiagnosed as material from costochondral junction.[2] The myxoid or chondroid stromal material can also be seen in other tumors like pleomorphic adenoma of bronchial glands, teratoma or pulmonary blastema.[5] However, the appearance of epithelial component helps in making a definite diagnosis.

PH has been found to be responsible for a significant rate of false positive malignant diagnosis in cases where there is dominance of epithelial cells showing some cytologic atypia with variation in nuclear size. The most common false positive diagnosis are carcinoid tumor, adenocarcinoma and small cell carcinoma.[3] Identification of the characteristic components of PH including the presence of the typical stromal components should allow the distinction to be made. S-100 positivity of the stromal material may be useful in supporting the diagnosis.

To conclude, transthoracic needle aspiration is an efficient and valuable method to achieve the diagnosis of PH. Recognition of this condition by FNAC is important as it can be managed conservatively and major surgical procedures can be avoided.