SLIDES & TRANSCRIPTS
Tuesday, June 19

ANATOMIC CONSIDERATIONS OF LYMPHATIC PATHWAYS IN THE LUNG AND MEDIASTINUM AND ITS INFLUENCE ON SURGICAL AND OTHER LOCAL THERAPIES

Hisao Asamura, MD

In my presentation there are two points. One is the anatomic considerations of lymphatic spread in lung cancer. And the second point is the analysis of sub-centimeter cancers resected in our institute, maybe a good comparison with Dr. Miller's data, presented afterwards.

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Studies of the lymphatic pathways have been done. This is a very old and a new problem, as well as a very important problem in the thoracic surgical community, because this is cross-related to mode of the surgical resection, and the extent of the lymph node dissections. This study has been done by a gross anatomic dissection of cadavers, like Dick Rubia's(?) study 30 or 40 years ago. In vivo radioisotope sensographic studies using a gallium injection, or a sentinel node navigation surgery may be presented by the other speakers. These are clinical studies of metastasis and metastatic nodes of actual N2 lung cancer patients.

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Now I first presented my own prospective study on 166 N2 patients. This is a study conducted on 166 non-small cells lung cancer patients. They were resected, with at least a lobectomy, and they underwent a complete hilar and mediastinal lymph node dissection. So I have studied the pattern of the lymph node spread according to the primary site of the tumors. The distribution of the primary lobe of tumor involvement is as follows. In the right upper lobe, 54; right middle lobe, 8; right lower lobe, 41; upper segment of the left upper lobe, 34; the lingular segment, 10; and left lower lobe in 19 patients. The pattern of lymphatic spread was studied. And this is the incidence of metastasis in key stations. This is number 3, number 7, number 5. Number 3 in Japanese map corresponds to 4R or 4L in the US map. In the right side we can see for right upper lobe tumors, a higher incidence of pre-tracheal lymph node stations, that very, very low incidence of carinal stations occurred. But for both the middle and lower lobe tumors, both lymph node stations are involved.

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We can speculate two major lymphatic pathways. Number 10 means the nodes around the main stem bronchus, going up to the superior mediastinum. This is one way. And the other way is going below the carina and up to the superior mediastinum or even contralateral side. I can say that for right upper lobe tumors, the tumors mainly use this loop number 1 only, but for middle and lower lobe tumors, they use both 1 and 2. These are the results of the left side. A very, very similar pattern can be seen for upper segment tumors. The metastasis for subcarinal nodes is not so common. Instead in other lobar segments, both lymph node stations are involved. In the left side also, these two lymph node pathways are speculated, and for upper lobe, upper segment tumors, use only this one way.

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So these are the conclusions. There are two major pathways in both sides, in the left side. So basically upper lobe or upper segment tumor use only loop 1, and for middle and lower lobe tumors, uses both major lymphatic pathways. So at present, our basic attitude is changing the extent of lymph node dissection according to the site of the primary tumors, which is not uniform extent of dissection.

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The second point is our experience of lymph node involvement and prognosis for resection of sub-centimeter lung cancers. From our pathology file, I can pick up 52 cases of sub-centimeter lung cancers. This is only 2.7% of all the resected cases during the same period. It's a very, very small proportion.
Among these 52 cases, 3 cases were an early hilar type of squamous carcinoma, which can be detected only by bronchoscopy. So the remaining 49 cases are located in the periphery of the lung. So I mainly focus on these 49 cases. These cases underwent various extent of pulmonary resections with and without hilar or mediastinal lymph node dissection. The important thing is that among the 49 cases, there are 30 lesions that can be already presented by Dr. Yankelevitz's presentation. Solid lesions were seen in 21 cases, and GGO BAC type lesion were seen in 28 cases. I think that we can differentiate that these two type of lung cancers.

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This is the simple type of GGO lesion. And this lesion is only the GGO part. This is the example of the GGO BAC type of lesions. This is the method of the discovery of the lesion in these 49 cases. In 17 patients, the lesion was found by chest x-ray screening. In 10 patients, CT screening. Two patients were found by sputum screening. These are squamous cell carcinoma. And incidental chest x-ray is 7 cases. And the incidental CT scan is 13 cases. Incident means a by chance CT or by chance chest x-ray, which was conducted for other reasons, a persistent cough or something.

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Among these incidental chest x-ray detected or CT detected cases, 6 cases are symptomatic, but of course these symptoms was not directly associated with the nodule itself.

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This is the preoperative diagnostic work-up for these 49 lesions. In 27 cases, the diagnostic work-up was not performed. And in 22 cases, it is performed. The breakdown was like here: fine needle biopsy, transbronchial biopsies, sputum, CT guided fine needle biopsy, CT guided transbronchial biopsy. In about half of the cases, positive results for malignancy was obtained, but in the others it was not obtained.
[Slide]

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And this is the pathological results of these 49 cases. Of the 28 GGO BAC type of lesions, they are adenocarcinoma with minimal invasion, or bronchoalveolar carcinoma. Actually, of the 28 cases, we can find only one case of Type C Noguchi's classifications. All the other 27 cases were classified according to Noguchi's classification, either A or B. So this is a bronchoalveolar carcinoma. In the solid tumors, adenocarcinoma in 17; squamous cell carcinoma in 2, small cell carcinoma, and carcinoid tumor in 1 each.

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These are the surgical interventions for the sub-centimeter lung cancers. For solid tumors, we basically chose a lobectomy of course. But in the other four cases, for some functional reasons, we did limited resections. But for GGO BAC type of lesions, we have made only 13 cases for lobectomy. For the other 15 cases, we have done a limited resection. Five of the 13 lobectomy were performed by VATS lobectomy.

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This is the lymph node involvement of these 49 cases. Of course in the 20 cases of GGO BAC type lesions there was no lymph node involvement, and no recurrence of the tumor. But in the 21 solid tumors, N1 involvement was seen two cases, and N2 involvement in one case. And two of these three cases had a recurrence. Of course these patients may have their poor prognosis, but they are still alive with disease. So I can say that's the only solid tumors we can see lymph node involvement and recurrence.

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So my conclusion is here. Even for sub-centimeter lung cancers, higher mediastinum lymph node metastasis might happen, but in many sub-centimeter lung cancers, lymph node metastases was seen only in solid type, not in GGO BAC type of lung cancer. Therefore, for GGO BAC type lesions, systematic hilar mediastinal node dissection may not indicated. Even for lobectomy, it may not be indicated. For solid type lesions, at least nodal assessment of key stations during thoracotomy should be performed, and still for solid type of lung cancer, lobectomy is indicated.
Thank you for your attention.

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