Pulmonary Blastomas

Path. Res. Pract. 184, 306-311 (1989)

Pulmonary Blastomas Immunohistochemical Investigations of Three Cases D. Dienemann Institut fOr Pathologie, Klinikum Steglitz, Freie Universitat Berlin, FRG

C.-A. Hartmann and C. Minck Pathologisches Institut, Krankenhaus Spandau, Berlin, FRG

SUMMARY

Three cases of pulmonary blastoma (PR) were investigated microscopically with conventional stainings and immunohistochemically with monocloncal antibodies to cytokeratin, vimentin, desmin and neurofilament protein. The tumors differed in terms of morphology as well as of immunohistochemistry. Two were epithelial and mesenchymal mixed tumors, and the remaining one was a monophasic tumor of a typical blastemic character. The two mixed tumors also differed from each other. In one of them, the epithelial and mesenchymal component expressed cytokeratin and vimentin in a clear-cut manner without any transition. The other mixed tumor displayed a gradual epithelial-to-mesenchymal transition accompanied by a switch in the expression ofcytokeratin and vimentin. The third tumor was ofpure mesenchymal origin, expressing vimentin in the majority ofcells and desmin in few cells. It is concluded that the PR is a morphologically and histogenetically heterogeneous tumor. Metaplastic changes may take place within a PB and make the recognition of embryogenesis more difficult.

Introduction

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PBs are rare neoplasias of the lung occurrin largely in man. The term was coined by Spencer in 1961 3 , who gave the histological description of a biphasic structure with 'epithelium-lined tubules and well formed stroma producing reticulin and collagen fibres'. The first description, however, was given by Barret and Barnard5 and Barnard4, the latter applying the term 'embryoma of the lung' because of the similarity of the tumor with embryonal lung tissue. The literature has so far reported about 120 cases3, 8, 13, 15, 16, 18-20,24-26,28,31,35,37, 41, ~ as well as 3 tumors of the same kind located in the upper respiratory tract ll ,27,30. Francis and Jacobsen 12 give a synopsis of the majority of cases from the literature including 11 cases of their own. These authors extended the definition of PB and included cases with a monophasic structure but an 0344-0338/89/0184-0306$3.50/0

otherwise typical blastemic character. The histogenesis of PB has not yet been clarified and is discussed controversially in the literature. Material and Methods Three lobectomy specimens were examined light-microscopically after formalin fixation and paraffin embedding. The diagnosis of PB had been made in each case according to the criteria of Francis and Jacobsen12 . Staining was done with H & E, Domagk-Elastica, PAS and Prussian blue. The immunohistochemical stainings were performed according to the alkaline phosphatase-anti alkaline phosphatase (APAAP) method 7 using new fuchsin as the alkaline phosphatase substrate4o• The following monoclonal antibodies were applied: 1) KL 143 , directed to 55-57 kd keratin polypeptides (Immunotech, Marseille, supplied by Dianova, Hamburg). © 1989 by Gustav Fischer Verlag, Stuttgart

Pulmonary Blastomas . 307 2} V 929 , directed to the 57 kd vimentin polypeptide (Dakopatts, Glostrup, Denmark). 3} DE-R-l1 lO, directed to the 53 kd desmin polypeptide (Dakopatts, Glostrup, Denmark). 4} NF 9, directed to the 200 kd polypeptide of the neurofilament protein triplet (Bio-Science, Emmenbriicke, Switzerland).

Results

Case Reports Case No.1: A 43-year-old man was admitted with the radiographic finding of a tumor in the third segment of the right lung. The resection specimen of the segment revealed a PB 4,5 cm in diameter. Nine months later, there was a local recurrence involving the parenchyma of the lung and the thoracic wall. Lobectomy and resection of two ribs disclosed a tumor 6 cm in diameter, which surprisingly exhibited the structure of an adenocarcinoma with mucus formation. Careful examination only at the periphery of the tumor within the scar resulting from the previous operation revealed a small focus with the typical structure of the formerly diagnosed PB. The patient died two weeks postoperatively due to complications resulting from the operation. Case No.2: A 67-year-old man presented with the radiographic finding of a tumor dorsobasal in the right lung. After lobectomy and resection of the partly involved

diaphragm a tumor of 10 cm diameter was found and classified as PB. Postoperatively irradiation was applied. The patient died one year later, post-mortem was not performed.

Case No.3: A 34-year-old man was admitted with the radiographic finding of a tumor in the apex of the left lung. Lobectomy revealed a PB 6,5 cm in diameter. Alocal recurrence necessitated the application of irradiation and chemotherapy. The patient died 22 months postoperatively. The post-mortem revealed an extensive local recurrence and metastases in both lungs, the mediastinal lymph nodes, the stomach and the brain.

Morphological and Immunohistochemical Findings

Case No.1: Microscopically, the tumor exhibited a striking biphasic pattern: equally dispersed tubular structures lined by cuboid epithelia with large but uniform rounded nuclei were embedded in a mesenchyma-like 'stromal' tissue consisting of rather large and mostly longish cells with oval nuclei and generally resembling fetal lung tissue of the first trimenon. The immunohistochemical examination likewise revealed a clear-cut biphasic pattern with a strong expression of cytokeratin and a lack of vimentin in the epithelia and the reverse in the 'stroma'. Neurofilament protein and

Fig. 1. Case No. 1. a} Biphasic pattern with tubular epithelial structures embedded in a mesenchyma-like 'stromal' tissue (H & E, x 200). b} Expression of cytokeratin exclusively by the tubular structures (KL 1 antibody, x 200). c} Expression of vimentin exclusively in the 'stromal' part (V 9 antibody, x 200).

308 . D. Dienemann, C.-A. Hartmann and C. Minck

desmin were not expressed. - In the local recurrence, the small area with the residual PB showed the described staining pattern, whereas the predominant part with an adenocarcinoma structure contained tumor cells that expressed cytokeratin only.

Case No.2: This tumor showed a monophasic pattern lacking epithelial differentiation. Besides large areas consisting only of small lymphocyte-like cells with round nuclei and scanty cytoplasm, there were numerous spots of undifferentiated spindle-shaped cells loosely arranged around irregularly structured blood vessels in a pseudorosette-like pattern. While cytoplasm was likewise scanty in most spindle cells, some of them had an ample amount but lacked any visible cross-striation. The mitotic frequency ranged up to 30 mitoses/HPF. The immunohistochemical examination revealed no expression of cytokeratin or neurofilament protein. Nearly half of the cells, both round and spindle-shaped, expressed

vimentin in varying quantities. However, approximately 5% of the perivascularly arranged spindle cells exhibited a strong expression of desmin.

Case No.3: Microscopically, the tumor showed a mixed pattern with morphologically clear-cut epithelial and mesenchyma-like components. The epithelial component mainly consisted of compact areas but focally revealed a trabecular pattern and, mainly at the tumor periphery, had a glandular (partly tubular or papillary) structure. The epithelial cells themselves also differed morphologically. Besides a majority of uncharacteristic polygonal cells, there were areas with keratinizing squamous cells as well as areas resembling a clear-cell carcinoma with typical hobnail cells. The mesenchyma-like component consisted partly of spindle or triangular-shaped cells in a loose perivascular arrangement. Moreover, there were large chondroid areas showing a striking gradual transition into epithelial areas.

Fig. 2. Case No.2. a) Monophasic pattern. Blastemic appearance with undifferentiated spindle cells arranged around blood vessels (H & E, x 122). b) Expression of desmin by some of the spindle cells (arrows), whereas the majority of cells is desmin-negative (DE-R-ll antibody, x 304).

Pulmonary Blastomas . 309

Fig. 3. Case No.3. a) Epithelial area (bottom) with gradual transition into chondroid area (H & E, X 200). b) All epithelial cells express cytokeratin. The cytokeratin-expression vanishes more and more with transition into chondroid area (KL 1 antibody, x 200). c) Chondroid area. Some of the chondroid cells express cytokeratin (arrows) (KL 1 antibody, x 200). The vast majority of epithelial cells expressed cytokeratin to different degrees, a small portion of cells showing a coexpression of vimentin. In the mesenchyma-like areas with perivascular arrangement, cytokeratin was likewise expressed by the majority of cells and vimentin by some of them. In the chondroid areas, the labeling was different: Cytokeratin expression was evidenced by the chondroid cells adjacent to the epithelium but vanished more and more at some distance, where a transition to vimentin expression was observed. No expression of neurofilament protein or desmin was detected. More clinical and radiographical details as well as histopathological descriptions of the cases have been published recently!5,34.

Discussion There have so far only been few publications with immunohistochemical investigations of PB. Scully et al. 36 examined one case, Addis and Corrin! four cases with antibodies to cytokeratin, which was expressed only in the epithelial and not in the stromal cells. Korbi et al.22 examined one case and found an expression of vimentin in mesenchymal as well as in blastematous areas, of desmin in mesenchymal areas, and of cytokeratin and epithelial membrane antigen in epithelial as well as in blastematous areas. Heckman et al.!6 found an expression of myoglobin, actin, desmin, and vimentin in two cases of PB with rhab-

domyosarcomatous differentiation. The three tumors we examined differed extraordinarily in their morphological and immunohistochemical aspects, suggesting that PBs are histogenetically heterogeneous tumors and that all three modes of histogenesis outlined in Table 1 may thus be possible. The first tumor, morphologically resembling embryonal lung tissue of the first trimenon, revealed a constant and distinct intermediate filament pattern with expression of cytokeratin exclusively in the epithelial cells and vimentin in the stromal cells without any transition. Even some particularly large epithelium-like 'stromal' cells strongly expressed vimentin but showed no cytokeratin coexpression. It can be assumed on morphological grounds that we are not dealing with an ordinary tumor stroma of a reactive nature but with a neoplastic component of stroma-like appearance. Neither the purely epithelial nature of the recurrence in this case nor the fact that Tarnai et al. 4! obtained a purely epithelial tumor after serial passages of a biphasic PB in nude mice is a solid argument against the neoplastic character of this sort of 'stroma'. Anyway, metastases and recurrences of PB as well as carcinosarcomas may differ morphologically from the primary tumor in displaying only one of the two components, i.e. epithelium or mesenchyma!2,39. In our opinion, we are dealing here with an epithelial and mesenchymal mixed tumor with the peculiarity of an organoid arrangement of the two components. This is in contrast with carcinosarcomas, where the epithelial and mesenchymal components are intermingled irregularly.

310 . D. Dienemann, C.-A. Hartmann and C. Minck

Table 1. Hypotheses concerning alternative developmental pathways of pulmonary blastomas Histogenesis primary epithelial (possibly secondary metaplasia towards mesenchyma) mixed epithelial and mesenchymal from the beginning mesenchymal

Embryogenesis entodermal

Authors Amemiya et al. 2 Tamai et al. 41

a) mixed tumor originating from two germ layers, i.e. mesoderm and entoderm b) mixed tumor originating from one germ layer, i.e. mesoderm mesodermal

McCann et al.26 Roth and Elguezabal35 Francis and jacobsen12

The second tumor, which expresses vimentin in about 30% of the cells and desmin in some of them, but lacks any epithelial features, presents differential-diagnostic difficulties because of its being monophasic in appearance and obviously of purely mesodermal origin. The question arises whether we are dealing here with a myosarcoma rather than a PB. Francis and Jacobsen 12, in some of their published cases of PB, described a muscular differentiation and also included such cases with a monophasic appearance but arrangement of tumor cells around thin blood vessels yielding a typical blastemic character. Other authors 21 ,23 think that a stereotypic adenocarcinoma of fetal type may possibly correspond to a PB. That means the PB/sarcoma and PB/carcinoma borderline may be vague in some cases. In our opinion, the expression of desmin by some of the tumor cells in this case does not permit the conclusion that the whole tumor must be of muscular origin throughout. Considering the striking perivascular arrangement of tumor cells, we favour the diagnosis of PB with 'maturation' of some tumor cells towards myoid cells, as su§~ested by Francis and Jacobsen 12• According to Spencer and Heckman et aJ.l6, some PBs evidence extensive areas with rhabdomyomatous features and may therefore be misinterpreted as rhabdomyosarcomas. The third tumor, besides its predominant epithelial parts, exhibited divergently differentiated mesenchymal structures as well as immature blastemic structures. It is striking that not only the morphologically definite epithelial cells but also the blastemic and chondroid cells partly express cytokeratin with a gradual transition from epithelial to stromal areas, immunohistologically corresponding with a decrease of cytokeratin expression and an increase of vimentin expression. This case likewise involves an epithelial and mesenchymal mixed tumor, but, in contrast with case No.1, the findings suggest a purely epithelial nature with transformation of the tumor cells with regard to their shape and the pattern of intermediate filaments expressed. The case supports other findings of metaplastic transformation of neoplastic epithelial cells towards mesenchymal cells in PBS41 , carcinosarcomas of the lung 1 and analogous tumors of the nasal cavity and paranasal sinuses32 • The variety of published considerations (Table 1) shows that the histogenesis of PB is uncertain. The strong expression of cytokeratin by chondroid cells as well as in blastemic areas of our third case points out that it may sometimes be impossible to draw histogenetic conclusions from

Spencer38

only morphological investigations with conventional histological stainings. On the other hand, it is also impossible to determine the histogenesis of tumors in a simple way by defining the intermediate filament expression. This is because there is increasing evidence that different intermediate filaments may be coexpressed in neoplastic and non-neoplastic tissues and that the pattern of expressed intermediate filaments may change, e.g. in tissue cultures and during embryological development6, 14, 17,33. On the contrary, it is indispensable to make a careful interpretation considering morphological as well as immunohistochemical findings and additionally taking into account dynamic aspects such as the possibility of metaplastic changes in tumors. To be sure, one should remember that the terms epithelium and mesenchyma are defined morphologically and functionally but not embryologically. Hence, the immunohistochemical analysis of intermediate filament expression, being helpful in the distinction between epithelium and mesenchyma, will make it possible to determine the histogenesis but not the embryogenesis, i.e. the derivation from a certain germ layer. Our investigations demonstrate that PBs are heterogeneous tumors morphologically as well as histogenetically. The question arises whether monophasic tumors with blastemic features, as in case No.2, should be included in PB according to Francis and Jacobsen 12 , or whether they should be classified as undifferentiated sarcomas. As for the biphasic tumors, these are really mixed epithelial and mesenchymal tumors, but it continues to be uncertain whether they originate from one germ layer only (mesoderm) or from two germ layers (mesoderm and entoderm). Acknowledgements For skillful technical assistance we are grateful to Mrs. I. Winter, Mrs. D. Wollensak and Mr. L. Oehring. References 1 Addis Bj, Corrin B (1985) Pulmonary blastoma, carcinosarcoma and spindle-cell carcinoma: an immunohistochemical study of keratin intermediate filaments. j Pathol147: 291-301 2 Amemiya R, Kodama T, Shimasotu Y, Koide T (1977) Three cases of pulmonary blastoma, with special reference to differential diagnosis from 'carcinosarcoma' and 'mixed tumor' of salivary gland type. jap j Cancer Clin 23: 123-131 3 Ashworth TG (1983) Pulmonary blastoma, a true congenital neoplasm. Histopathology 7: 585-594 4 Barnard WG (1952) Embryoma of lung. Thorax 7: 299-301

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Received January 25, 1988 . Accepted in revised form October 21, 1988

Key words: Pulmonary blastoma - Lung tumors - Monoclonal antibodies - Intermediate filaments - Histogenesis Dr. D. Dienemann, Institut rur Pathologie, KIinikum Steglitz der Freien Universitiit Berlin, Hindenburgdamm 30, D-1000 Berlin 45, FRG