Indian Journal of Pathology and Microbiology

: 2014  |  Volume : 57  |  Issue : 1  |  Page : 89--91

Case of pulmonary pneumocytoma: A probable cytological diagnosis with histopathological confirmation

Mayank Gupta1, Jigar Shah2, Marie Therese Manipadam3, Vinay M Rao4,  
1 Assistant Professor, Department of General Pathology, Christian Medical College, Vellore, India
2 PG Registrar, Department of General Pathology, Christian Medical College, Vellore, India
3 Professor, Department of General Pathology, Christian Medical College, Vellore, India
4 Assistant Professor, Department of Cardiothoracic Surgery, Christian Medical College, Vellore, India

Correspondence Address:
Mayank Gupta
4th floor ASHA Building Department of General Pathology Christian Medical College Vellore - 632 004, Tamil Nadu


Pneumocytoma is a rare benign tumor of the lung that usually presents as a solitary pulmonary nodule. It is believed to arise from the primitive undifferentiated respiratory epithelium. We report a case of pulmonary pneumocytoma that was suspected on needle aspiration smears and confirmed histologically. This case describes the cytological features of pneumocytoma that are rarely described in textbooks.

How to cite this article:
Gupta M, Shah J, Manipadam MT, Rao VM. Case of pulmonary pneumocytoma: A probable cytological diagnosis with histopathological confirmation.Indian J Pathol Microbiol 2014;57:89-91

How to cite this URL:
Gupta M, Shah J, Manipadam MT, Rao VM. Case of pulmonary pneumocytoma: A probable cytological diagnosis with histopathological confirmation. Indian J Pathol Microbiol [serial online] 2014 [cited 2021 Sep 26 ];57:89-91
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Pulmonary pneumocytoma, also known as sclerosing hemangioma, is a rare benign tumor of uncertain histogenesis. The term "sclerosing hemangioma" is a misnomer as it is not a true vascular neoplasm. [1] Initially, the origin of this tumor was doubtful but now it is believed to be derived from the primitive undifferentiated respiratory epithelium. [2] Histopathological features of pneumocytoma have been described previously; however, the cytological features are rarely described. We herein report a case in which pulmonary pneumocytoma was suspected on needle aspiration smears and was confirmed by histopathological examination.

 Case Report

A 43-year-old female was referred from an outside hospital to the Department of Cardiology, Christian Medical College (CMC), Vellore, for recurrent paroxysmal supraventricular tachycardia and she underwent radiofrequency ablation for the same. A coin-shaped lesion in the middle lobe of the right lung was detected on routine chest X-ray performed at that hospital. Subsequently, she underwent computed tomography-guided fine needle aspiration (FNA) for the lung lesion at that hospital. FNA smears of the lung lesion without cell block were sent to the Department of General Pathology at CMC Vellore for review. Smears were cellular and showed two population of cells; one with clusters and few acini of round to polygonal (surface epithelial) cells displaying mild anisonucleosis, fine chromatin and pale cytoplasm. The second population comprised of dispersed (stromal) cells displaying round to oval nuclei, slightly coarse chromatin and scant cytoplasm [Figure 1]. Based on the cytomorphology, pneumocytoma was suspected. As there was no cell block available for immunohistochemistry, diagnosis of pneumocytoma could not be confirmed. The patient did not give consent for repeat FNA and underwent right middle lobectomy. The specimen weighed 60 g, measuring 10 cm 7 cm 3.7 cm. A well-circumscribed grayish white firm tumor measuring 2.8 cm 2 cm 4 cm, 0.2 cm from the pleural surface and 2.2 cm from the endobronchial resection margin, was evident. Adjacent lung parenchyma appeared unremarkable. Microscopically, the tumor was well circumscribed and composed of proliferated tubular structures lined by a layer of surface cuboidal cells surrounded by sheets of polygonal (stromal) cells with clear to foamy cytoplasm and centrally placed vesicular nuclei [Figure 2]. Several intervening thin-walled dilated vascular channels were present. Cellular atypia, necrosis and mitotic figures were not evident. On immunohistochemistry, stromal cells expressed CD10 and vimentin but did not express cytokeratin [Figure 3]a and thyroid transcription factor (TTF-1) [Figure 3]b. Weak expression of epithelial membrane antigen (EMA) was seen in the stromal cells compared with the surface epithelial cells. Epithelial cells lining the tubules strongly expressed cytokeratin [Figure 3]a, EMA and TTF-1 [Figure 3]b but did not express vimentin and CD10. Smooth muscle actin (SMA), desmin, HMB-45, melan A, neuron-specific enolase (NSE), synaptophysin and S-100 were negative in both surface epithelial cells and stromal cells. Based on the above histomorphological features and immunoprofile, a diagnosis of pneumocytoma was made.{Figure 1}{Figure 2}{Figure 3}


Pneumocytoma is a rare benign tumor of the lung, first described by Liebow and Hubell. [3] They considered this tumor to be of vascular (endothelial) origin due to prominent angiomatoid features and coined the term sclerosing hemangioma. However, now, these tumors are not considered to be of vascular origin as they are immunonegative for CD34, CD31, factor VIII and Ulex europaeus agglutinin. [1] Nagata et al. reported the presence of intracytoplasmic surfactant apoprotein in both stromal and epithelial cells thus supporting the epithelial origin of this tumor. [4]

Clinically, this tumor is common in middle aged adults, with a female predominance. [2] It is incidentally detected during routine radiographic examination, as a solitary and peripherally located lesion, [2] which is similar to our case. The lower lobe is commonly involved; however, it can involve any lobe. [1] In our case, the tumor involved the right middle lobe. Some patients may present with hemoptysis, chest pain and cough. [2]

Gal et al. described salient cytopathological features of pulmonary pneumocytoma. [5] In their report, they described two populations of cells:

Type A (surface epithelial) cells comprising of polygonal to fusiform cells, arranged in small strips and clusters, displaying finely stippled chromatin, indistinct nucleoli and few with fine nuclear grooves and Type B (stromal) cells arranged in sheets displaying bland oval nuclei, slightly coarse chromatin and scant cytoplasm. Scattered alveolar macrophages, clumps of hemosiderin pigment and multinucleate giant cells were also seen. The hematoxylin and eosin-stained sections from the cell block also revealed two populations of cells as described above. Similarly, in our case, two populations of cells were evident on smears but no cell block was available for confirming the diagnosis of pneumocytoma. Gottschalk-Sabag and Sant also reported cases of pulmonary pneumocytoma diagnosed by FNA cytology. [6],[7]

In a resected specimen, the tumor is well circumscribed and has a solid grey to tan yellow cut surface. [2] Histologically, the tumor can have papillary, solid, hemorrhagic or sclerotic patterns and is composed of surface epithelial cells and round stromal cells, both of which are considered neoplastic. [2] Niho et al., based on an X-chromosme-linked polymorphic marker, human androgen receptor, concluded that pneumocytoma is a neoplastic lesion and both the cells of the tumor have a common origin, i.e. they are monoclonal. [8] The study by Sartori and colleagues did not reveal molecular alterations in epithelial growth factor receptor, human epidermal growth factor receptor 2 and K-ras sequencing, whereas allelic losses at p16 and RB loci with identical microsatellite allelic loss patterns were present in both the cellular components. [9] However, Wang et al. concluded that stromal cells are true tumor cells originating from the primitive respiratory epithelium while surface epithelial cells originate from the reactive proliferation of type-II pneumocytes. [10] Thus, due to conflicting results, further studies are required to confirm whether these two cell types are monoclonal or not.

The tumor, in our case, showed tubular structures lined by a layer of cuboidal (surface) cells surrounded by solid sheets of polygonal cells [Figure 2]. Papillary architecture, sclerosis or areas of hemorrhage were not evident. Devouassoux - Shisheboran et al. described immunohistochemical features of 100 cases of pulmonary sclerosing hemangioma in which both surface epithelial cells and stromal cells were positive for EMA and vimentin. [2] Most of the cases showed nuclear positivity for TTF-1 in both surface cells and stromal cells, while pancytokeratin was positive in surface epithelial cells only. [2] CK20, CK5/6, S-100, SMA, calretinin, synaptophysin, chromogranin and leu-7 (CD57) were negative. [2]

In about 61% of the cases, the tumor expressed progesterone receptor (PR) in the stromal cells while only few cases (about 7%) expressed estrogen receptor (ER) in the stromal cells. [2] Surface cells were negative for both ER and PR. [2] As this tumor is common in females, it is speculated that the female sex hormone, particularly progesterone, induces proliferation of undifferentiated primitive respiratory epithelium. In our case, surface cells strongly expressed pancytokeratin [Figure 3]a, TTF-1 [Figure 3]b and EMA, similar to the study by Devouassoux - Shisheboran et al., but did not express vimentin. [2] The stromal cells expressed vimentin but did not express cytokeratin [Figure 3]a, similar to the study by Devouassoux - Shisheboran et al., and did not express TTF-1 [Figure 3]b, which was in contrast to their findings. [2] Faint expression of EMA was seen in the stromal cells. The expression of CD10 was confined to the stromal cells while the surface cells were negative. CD10 expression in pulmonary pneumocytoma has not been reported in the literature before; therefore, further studies are required to evaluate the expression of CD10 in this tumor.

The most important differential diagnoses at the cytological level are carcinoid and other benign tumors of the lung, such as alveolar adenoma. The presence of a dual cell population on the smears favors pneumocytoma. However, the diagnosis has to be confirmed by immunohistochemistry. Thus, paraffin-embedded cell block preparation is required to confirm its diagnosis on smears. At the histopathological level, the differential diagnosis includes alveolar adenoma, clear cell (sugar) tumor, metastatic clear cell renal carcinoma, primary clear cell carcinoma and carcinoid. In our case, the presence of a dual cell population with the absence of malignant features ruled out these possibilities. Moreover, negative expression of S-100, HMB-45 and melan A ruled out clear cell tumor. Expression of TTF-1 in the surface epithelial cells ruled out metastatic clear cell renal carcinoma. NSE and synaptophysin were negative and thus a diagnosis of carcinoid was ruled out.

Wedge resection or lobectomy is the treatment of choice for pneumocytoma. This tumor usually has a benign course, but there have been instances where pleural and lymph node metastasis have occurred. [1] Therefore, close follow-up of these patients is required. As far as our case is concerned, the post-operative period and follow-up were uneventful.

In conclusion, this case emphasizes the importance of diagnosing pulmonary pneumocytoma at the cytological level by identifying a dual cell population and preparing cell block for immunohistochemistry. Awareness of this entity is required for proper evaluation of a solitary pulmonary nodule. If salient cytological features of pneumocytoma are evident on FNA smears, confirmation by immunohistochemistry can guide the clinician in appropriate management.


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