Ultrastructure of tumour invasion and desmoplastic response of bronchogenic squamous cell carcinoma

Clinicopathologic characteristics of peripheral squamous cell carcinoma of the lung

Squamous cell carcinoma of the lung can be divided into two types according to the location of the primary site: the central type and the peripheral type. The clinicopathologic factors in the peripheral type of lung squamous cell carcinoma have not yet been fully evaluated. A total of 204 surgically resected lung squamous cell carcinomas were reviewed with special reference to their location, histologic characteristics based on tumor growth patterns, and clinicopathologic factors. The central type and the peripheral type accounted for 95 and 109 cases, respectively. Although the patient population of the peripheral type was older, with a lower pathologic stage, lower lymphatic vessel involvement, and lymph node metastasis, the Kaplan-Meier survival proportions did not differ significantly between these two groups. Based on the histologic growth pattern, the peripheral type was classified under three subgroups as follows: 1). the alveolar space-filling type, 2). the expanding type, and 3). the combined type. Among these three types, the alveolar space-filling type showed neither lymphatic vessel invasion nor lymph node metastasis and had the most favorable prognosis. The central and peripheral types of lung squamous cell carcinoma have different clinicopathologic characteristics and should be classified under respectively different categories.

Laminin and type VII collagen distribution in different types of human lung carcinoma: correlation with expression of keratins 14, 16, 17 and 18

The expression patterns of basement membrane components and keratin intermediate filament proteins were studied in normal human bronchial epithelium and 56 lung carcinomas using monoclonal antibodies to laminin, type VII collagen and the individual keratins 14, 16, 17 and 18. In normal lung, laminin and type VII collagen were present between the epithelium and the lamina propria of bronchi and bronchioles. Keratin 14 was expressed in the basal cells, keratin 17 in the basal and some suprabasal cells and keratin 18 in the columnar cells of the bronchi and bronchioles. Keratin 16 was not present in normal bronchial epithelium. Laminin was found in all subtypes of lung carcinoma, but type VII collagen was present only in squamous cell carcinomas, where it showed a reduction in expression with decreasing differentiation. Type VII collagen was not identified in adenocarcinomas, small cell carcinomas or carcinoids. Antibodies to basal cell keratins 14 and 17 also displayed positivity only in squamous cell carcinomas, although no correlation with the degree of differentiation could be observed. Keratin 16 appeared to be a marker of the squamous phenotype, rather than of hyperproliferation. The keratin 18 marker for columnar epithelial cells showed a reaction pattern opposite to that of the basal cell keratins, being extensively present in adenocarcinomas, small cell carcinomas and carcinoids, with less expression in squamous cell carcinomas. This study shows a correlation between the presence of type VII collagen and the basal cell keratins 14 and 17, and a negative correlation between these components and keratin 18. These findings are likely to be useful in identifying lung cancer subtypes.

Prognostic significance of basement membrane deposition in operable squamous cell carcinomas of the lung

Tumor histology, stage of disease, and performance status are the most important prognostic factors in squamous cell lung cancer (SqCLC). A potentially important descriptor is the pattern of tumor growth as reflected in the dissolution of preexisting or deposition of newly formed basement membrane (BM) around tumor cell nests. The possible correlation between the pattern of BM deposition and patient survival was investigated. Immunohistochemistry testing, using polyclonal antibodies to human type IV collagen, was done on tumor samples of 68 patients with operable Stages I or II SqCLC, and BM staining was scored semiquantitatively. More than 75% immunoreactivity was scored as extensive BM and less than 75% as moderate or limited BM. In six patients, no immunoreactivity could be detected. In 27 of 62 patients, extensive and, in 35 of 62 patients, moderate-limited BM deposition was found. This deposition had a significant effect on survival (P = 0.02). Cox regression analysis, including BM deposition and tumor stage, indicated that BM deposition might also have value as an additional independent prognostic indicator for survival (P = 0.02). Deposition of an appreciable amount of BM in the center of the SqCLC was a prognostically favorable sign, independent of tumor stage.

Basement membranes in bronchogenic squamous cell carcinoma: an immunohistochemical and ultrastructural study

Basement membrane (BM) deposition at the inter-face of tumor cells and stroma was studied in 27 bronchogenic squamous cell carcinomas. Specimens from peripheral and central parts of each tumor were collected. These were frozen, formalin fixed and paraffin embedded or fixed in Karnovsky's fixative, and processed for electron microscopy. With the use of antibodies to type IV collagen and laminin, the BM was visualized by light microscopy with an indirect immunoperoxidase technique. Light microscopic findings were compared to ultrastructural observations. The peripheral parts of the tumors showed continuous BM in a recognizable preexisting alveolar pattern without evidence of invasive growth into the alveolar septa. In contrast, central parts showed highly variable BM deposition ranging from continuous to almost completely absent. Alveolar patterns were not observed in the tumor centers. The stromal compartment of the tumor centers contained many spindle cells with irregular pericellular BM-like material that could be identified ultrastructurally as myofibroblasts. Electron microscopy and immunohistochemistry yielded virtually identical results. It is concluded that invasive growth in bronchogenic squamous cell carcinomas occurs in central parts of the tumor when the tumor periphery shows expansive growth without invasion of alveolar septa. The situation is different in invasive squamous cell carcinomas originating from other organs because of anatomical differences between the lung and solid organs.

What's new in the ultrastructure of tumor invasion in vivo?

An important point emerging from the literature on tumor invasion in vivo is the great variability of nearly all aspects studied. It seems that there is neither one particular morphologic change which renders a cell invasive, nor one particular mechanism by which a cell crosses the boundaries of its original tissue compartment to occupy another. Nevertheless, some general trends are demonstrable. The majority of invasive tumor cells appear to be characterized by prominent surface protrusions, decreased junctional contacts and, in the case of epithelium-derived tumor cells, an incomplete basement membrane. The fact that some tumors can invade foreign tissues without loosing their basement membrane is emphasized. Invasive cells frequently form organized associations with preexistent non-neoplastic cells without damaging them. Apparently, the eventual disappearance of the preexistent cells in most invaded tissues is not necessarily due to a direct action on the part of the tumor cells. It rather seems a secondary phenomenon caused by, e.g., the insertion of invasive tumor cells between the preexistent cells and their original stroma. Very often, this seems to be due to the affinity of malignant cells for basement membranes. In addition, the adhesion of tumor cells to basement membranes frequently seems to determine their pattern of spread through a tissue. A process which may turn out to be a key factor in tumor invasion is desmoplasia, the series of host reactions which creates a new environment for the tumor cells which may favor their survival, proliferation, and locomotion. With the rapid development of new techniques, electron microscopy will probably contribute to the elucidation of the exact nature, the degree of similarity to granulation tissue, and the influence on invasion of desmoplastic tumor stroma.