Lysis of type-I collagen by squamous carcinomas of the head and neck

Matrix metalloproteinases expression correlates with survival in patients with esophageal squamous cell carcinoma

OBJECTIVES

The matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases capable of degrading the extracellular matrix and play important roles in malignancies. We evaluated the expression of four MMPs in esophageal squamous cell carcinoma (ESCC), and assessed the association between MMP expression and clinicopathologic characteristics and disease-free survival time.

METHODS

We evaluated MMP1, MMP7, MMP9, and MMP13 expression in tissues from 208 patients with ESCC using immunohistochemistry (IHC), and correlated MMP expression to clinicopathologic characteristics and disease-free survival time. To confirm MMP9 expression at different levels, we simultaneously performed RT-PCR, Western blotting, and IHC on tissues from a separate cohort of 23 patients with ESCC.

RESULTS

IHC analysis showed that 63.0%, 41.8%, 49.0%, and 32.2% of 208 ESCC samples were positive for MMP1, MMP7, MMP9, and MMP13, respectively. MMPs were strongly expressed in the cytoplasm of cancer cells, especially in the invasive margin, and weakly expressed in stromal cells. No immunostaining was detected in non-cancerous esophageal mucosa. MMP9 expression was positively associated with poor tumor cell differentiation (p= 0.001), vessel permeation (p= 0.027), and lymph node metastasis (p= 0.027). MMP9 expression was a negative, independent predictor of disease-free survival time (Hazard ratio, 1.470; 95% CI, 1.105 approximately 1.955; p= 0.008). The expression of MMP7 (median survival time: 23 months for MMP7 positive patients, >77 months for MMP7 negative patients; p= 0.001) and MMP13 (median survival time: 18 months for MMP13 positive patients, 39 months for MMP13 negative patients; p= 0.014) correlated negatively with disease-free survival in relatively early stage ESCC patients. Co-expression of MMP7, MMP9, and MMP13 in relatively early stage ESCC samples identified patients with a poor prognosis (13 months median survival time) compared to those lacking MMP7, MMP9, and MMP13 expression (58 months median survival time, p < 0.001).

CONCLUSIONS

MMP9 expression is a negative, independent prognostic factor in ESCC and correlates with tumor cell differentiation, vessel permeation, and lymph node metastasis. MMP7, MMP9, and MMP13 may function in early stage ESCC, and their co-expression predicts poor outcome for relatively early stage ESCC patients.

Neck dissection in oral cancer--clinical review and analysis of prognostic factors

The purpose of this study was to evaluate the oncologic effectiveness of radical and different types of modified neck dissections with preservation of the spinal accessory nerve, internal jugular vein and sternocleidomastoid muscle and to identify prognostic factors for regional control and survival in univariate and multivariate analysis. This retrospective study included 373 patients with squamous cell carcinoma of the oral cavity who underwent 401 neck dissections between January 1986 and December 1997 at the Department for Oral and Maxillofacial Surgery, Hanover Medical School. The actuarial neck control rate after 5 years was estimated with 87%. Neck failure occured only within the first 2 years after neck dissection. The number of positive nodes, macroscopic extracapsular spread, peeling off metastases from carotid artery and cranial base and preoperative radiochemotherapy were significant prognostic factors. Grade of metastases, microscopic extracapsular spread, lymphangiosis carcinomatosa and postoperative radiation showed no prognostic significance. The comparison of neck failures after radical and modified neck dissection demonstrated a tendency to improved regional control after radical neck dissection with increasing extent of neck disease.

Expression and regulation of collagenase-2 (MMP-8) in head and neck squamous cell carcinomas

MMP-8 (collagenase-2) is the most effective collagenase to initiate type I collagen degradation. Since initiation of lysis of the surrounding collagen matrix is an essential prerequisite for carcinoma cells to spread, this study investigated the expression of MMP-8 in squamous cell carcinoma (SCC) of the head and neck in vivo and in vitro. Most of the recently established head and neck carcinoma cell lines (22/25), corresponding tumour (5/7) and dermal (2/2) fibroblasts, commercial tongue carcinoma (HSC-3 and SCC-25), and transformed keratinocyte cell lines of the tongue (IHGK) and skin (HaCaT) expressed MMP-8 mRNA analysed by the PCR method. Western blotting revealed a latent 50 kD band in concentrated culture media of carcinoma cells and corresponding tumour and dermal fibroblasts. The expression of immunoreactive MMP-8 protein was reduced 30% by transforming growth factor beta-1 (TGF-beta1) at 1 ng/ml concentration and 60% at 10 ng/ml concentration, but up-regulated 2- and 2.5-fold after 10 nM and 100 nM phorbol 12-myristate 13 acetate (PMA), respectively. Immunohistological staining localized MMP-8 protein in a few malignant invading tumour cell islands, certain fibroblasts, polymorphonuclear neutrophils (PMNs), and plasma cells. In situ hybridization revealed a faint sporadic signal in carcinoma cells of all eight tissue sections analysed. It is concluded that tissue from head and neck carcinomas can express MMP-8 both in vivo and in vitro. Since the amount of MMP-8 in carcinoma and stromal cells is rather low, MMP-8 may have a potential role, with other collagenases, in the proteolysis of connective tissue associated with the spreading of invasive carcinoma.

The clinical significance of MMP-1 expression in oesophageal carcinoma

Matrix metalloproteinase-1 (MMP-1) is involved in the degradation of interstitial collagen and thus thought to play a role in invasion of carcinoma. We investigated 51 oesophageal carcinoma patients to clarify the significance of MMP-1. MMP-1 mRNA was demonstrated to be expressed exclusively in almost all carcinoma tissue specimens (T) (94.1%) by reverse transcription-polymerase chain reaction, but not found in normal mucosal tissue specimens (N). The mean T/N ratio of MMP-1 was 42.5 and cases with T/N > or = 10 had a higher incidence of cases involving muscularis propria than those with T/N < 10 which included all the cases involving the submucosa (P< 0.05). MMP-1 mRNA was significantly associated with both 40 kD (putative active MMP-1) and 50 kD (putative latent MMP-1) gelatinolytic bands (n = 17). These findings indicated that MMP-1 mRNA reflected the net function of MMP-1 and suggested MMP-1 to be involved in carcinoma invasive process. On the other hand, MMP-1 mRNA was inversely correlated with the patient prognosis (P< 0.01). These results indicated that MMP-1 might therefore play a crucial role in local invasion, but not in systemic dissemination. As a result, MMP-1 might be a novel prognostic factor independent from those previously reported in oesophageal carcinoma.

Matrix metalloproteinases in skin

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases collectively capable of degrading essentially all extracellular matrix components. These enzymes can be produced by several different types of cells in skin such as fibroblasts, keratinocytes, macrophages, endothelial cells, mast cells, and eosinophils and their activity can be specifically inhibited by TIMPs (tissue inhibitors of metalloproteinases), which bind to active MMPs with 1:1 stoichiometry. In general, MMPs are not constitutively expressed in skin but are induced temporarily in response to exogenous signals such as various cytokines, growth factors, cell matrix interactions and altered cell-cell contacts. At present, more evidence is accumulating that MMPs play an important role in proteolytic remodeling of extracellular matrix in various physiologic situations, including developmental tissue morphogenesis, tissue repair, and angiogenesis. On the other hand, MMPs play an important pathogenetic role in excessive breakdown of connective tissue components, e.g. in rheumatoid arthritis, osteoarthritis, chronic ulcers, dermal photoageing, and periodontitis, as well as in tumor cell invasion and metastasis. In this review we discuss the role of MMPs and TIMPs in human skin based on new observations on the regulation of the expression of MMPs, on their substrate specificity, and MMP expression in physiologic and pathologic conditions of skin involving matrix remodeling. Furthermore, therapeutic modalities based on regulating MMP activity will be reviewed.

Cell, tissue and organ culture as in vitro models to study the biology of squamous cell carcinomas of the head and neck

In vitro models are currently being used to study head and neck squamous cell carcinoma (HNSCC). Several hundred HNSCC cell lines have been established by various investigators and used to study a broad spectrum of questions related to head and neck cancer. The head and neck model with respect to multistage carcinogenesis is now complete. Several techniques exist for the culture of normal epithelial cells from the upper aerodigestive tract (UADT). The biology of these UADT cells (oral cavity, oropharynx, hypopharynx and larynx) is being studied. Successful culture of premalignant lesions (dysplastic mucosa, leukoplakia, erythroplakia) has resulted in establishment of a limited number of premalignant cell lines and cell cultures. HPV infection of normal oral epithelial cells for immortalization (approximately premalignant cells) coupled with transformation with carcinogens (malignant cells) has established an experimental model for progression. Two in vivo models for oral carcinogenesis, the 7,12 dimethylbenz(a)anthracene-induced hamster cheek pouch model and the 4-nitroquinoline-N-oxide rat oral model, have been established in culture. Thus, multistage carcinogenesis models have been established from both human tissues and animal models and include cultures of normal, premalignant and malignant cells. Culture techniques for growing dissociated primary tumor cells for short term experimental analysis are being used. The culture of normal or tumor tissue as organ/explant cultures allows for the maintenance of normal cell-cell and cell-matrix interaction, but limits experimentation since these cultures cannot be propagated. Several three dimensional model systems are being used to obtain this histological complexity but allow for experimentation. The ability to culture normal, premalignant and malignant cells coupled with the use of a variety of culture techniques, should allow for the continued growth and experimentation in head and neck cancer research.

Gene expression of interstitial collagenase (matrix metalloproteinase 1) in gastrointestinal tract cancers

Collagenolytic proteinases play an important pathological role in the invasion and metastasis of cancer cells. However, little is known about the role of interstitial collagenase (matrix metalloproteinase-1; MMP-1) in this process. To investigate the expression of the MMP-1 gene in cancer tissues, an in situ hybridization study was carried out in gastrointestinal tract cancers (one esophageal cancer, five gastric cancers, and four colorectal cancers), using a 35S-labeled MMP-1 cDNA probe. The MMP-1 gene was expressed in the stromal cells of fibrous tissue around cancer nests, especially at the margin of invasion and/or within the cancer nest; however, no definite expression within cancer cells was observed. Expression of the MMP-1 gene in the stromal cells was more common in well differentiated gastric adenocarcinoma than in poorly differentiated adenocarcinomas. These findings indicate that expression of the MMP-1 gene is greater in stromal cells that are closely associated with cancer cells, suggesting a pathophysiological role of MMP-1 in the invasion and metastasis of cancer cells.

Localization by in situ hybridization of mRNAs encoding stromelysin 3 and tissue inhibitors of metallo-proteinases TIMP-1 and TIMP-2 in human head and neck carcinomas

The presence and distribution of mRNAs encoding a matrix metalloproteinase (MMP) stromelysin 3 and two tissue inhibitors of MMP, TIMP1 and TIMP-2 have been studied by in situ hybridization of 18 human epidermoid head and neck carcinomas and four normal tissues. We found that in 16 tumors out of 18, stromelysin 3 mRNAs were only expressed by fibroblasts which were in close contact to invasive cancer cells. Tumor cells and normal tissues were not labeled. TIMP-1 mRNAs were detected in well differentiated cancer cells and in endothelial cells in all the cancers. In 13 out of the 18 carcinomas, TIMP-2 mRNAs were localized in only a few stromal cells near well differentiated invasive cancer cells and in endothelial cells. The significant expression of TIMP-1 and TIMP-2 mRNAS may lead to less aggressive MMPs, especially in the case of stromelysin 3, in the invasive process of the stroma.

Production of matrix metalloproteinase 2 (gelatinase/type IV collagenase) and 3 (stromelysin) by cultured oral squamous cell carcinoma

Matrix metalloproteinases (MMPs) are believed to play an important role in tumor invasion and metastasis. MMPs have been identified as proforms of malignant tumor-associated enzymes, such as procollagenase (proMMP-1) of M(r) = 53,000, progelatinase (proMMP-2) of M(r) = 72,000, proMMP-9 of M(r) = 92,000, and prostromelysin (proMMP-3) of M(r) = 59,000. Here we report that two cell lines of squamous cell carcinoma (SCC9 and SCC25) produce at least two matrix metalloproteinases (MMPs) in zymogen form, which have been identified as proMMP-2 and 3 by indirect immunofluorescence technique, immunoblot analysis, and gelatin-substrate gel enzymography. Additionally, a 92-kDa gelatinolytic metalloproteinase (proMMP-9) was detected by gelatin-substrate gel enzymography. We propose that the ability of these tumor cells to secrete MMPs plays an important role in the malignant behavior of oral squamous cell carcinomas.

Sequential degradation of interstitial collagen by metalloproteinases extracted from tumors of murine ascites hepatomas

Gelatinolytic and collagenolytic proteinases were separately isolated by different extraction methods from the mouse ascites hepatoma MH134, and from rat ascites hepatoma AH109A. The activities of two proteinases in each extract showed no significant differences, but after trypsin activation the activities of proteinases from the highly metastatic MH134 were significantly increased compared to the enzyme activities in AH109A, which has low metastatic potential. The total activities of collagenase and gelatinase were increased 7.2- and 5.1-fold; their specific activities were increased 5.2- and 4.8-fold, respectively. Gelatinase and collagenase from MH134 were characterized on gelatin zymography. The gelatinase had a molecular weight of 99 and activation by 4-aminophenylmercuric acetate (APMA) or trypsin resulted in its conversion to 79 or 79-95 kD, respectively. The collagenase revealed a major gelatinolytic band at 89 kD, which was converted to 85 and 70 kD by APMA-activation, and a minor gelatinolytic band at 60 kD. These proteinases could degrade native type I collagen to small fragments in a cooperative manner. Trypsin inhibitor, which affects the trypsin activation of latent gelatinase, was extracted together with gelatinase. The inhibitory activity of the enzyme from AH109A showed a 4.1-fold higher specific activity and 3.7-fold greater total activity than that from MH134. The proteinase(s) capable of activating the gelatinase was also extracted from MH134.

Proteolytic activity of first trimester human placenta: localization of interstitial collagenase in villous and extravillous trophoblast

In human placentation, events of implantation and early blastocyst development are mediated by fetal trophoblastic cells which penetrate into the maternal endometrium and myometrium. Although highly regulated in its biological behavior, trophoblast simulates a malignant neoplasm by virtue of invading the uterine wall and uterine spiral arteries and by embolizing throughout the systemic circulation. This process is at least in part dependant on the regulated production of proteolytic enzymes to degrade extracellular matrix. The most abundant extracellular protein is connective tissue type (interstitial) collagen. The uterine remodeling during the establishment of the embryo requires collagenase which catalyzes the initial step in the breakdown of collagen. This study demonstrates the presence of interstitial collagenase in villous and extravillous trophoblast of first trimester placenta using immunocytochemical methods on light microscopic and ultrastructural levels. Intracytoplasmic staining for interstitial collagenase was present in cyto- and syncytiotrophoblast covering the chorionic villi as well as in extravillous intermediate trophoblast invading spiral arteries in the placental bed. Furthermore, outgrowth cultures of chorionic villi were studied with the immunogold method. Gold labelling was associated with the cell surface of trophoblastic cells as well as with fibrillary collagen like proteins of newly synthesized extracellular matrix. We speculate that interstitial collagenase plays a role in the degradation of uterine collagen within the developing human placenta.

Low incidence of ras oncogene activation in human squamous cell carcinomas

Activation of the ras gene family by point mutation at codons 12, 13 and 61 has been demonstrated in up to 20% of unselected series of human tumours. The present study was carried out to assess the incidence of ras activation in 37 squamous cell carcinomas of the head and neck, seven squamous cell carcinomas of the skin and eight squamous carcinoma cell lines. Oligonucleotide probes and the polymerase chain reaction were used on DNA extracted from achival paraffin embedded material. Mutations in codon 12 of the Harvey ras gene was found in a carcinoma of the larynx and a carcinoma of the lip, both of which had received prior irradiation. A cell line (LICR-LON-HN8) established from the same laryngeal cancer showed the same mutation. This study indicates that there is a low incidence of ras mutation in human squamous cell carcinomas and that activation of this family of genes is probably not a common factor in the development of this group of tumours.

Morphological changes in a human scirrhous gastric carcinoma cell line (KATO-III) when cultured in collagen-coated dishes

The morphological differences between cells of a human scirrhous gastric carcinoma cell line (KATO-III) cultured in plastic dishes and in collagen-coated dishes were examined by phase-contrast and electron microscopy. When KATO-III cells were inoculated into plastic dishes, a few cells became attached to the surface of the dishes and the rest remained in suspension. However, when they were inoculated into collagen-coated dishes, they all remained in suspension. In both types of dish, most of the cells in suspension were single although a few were in clusters. The cells in suspension in collagen-coated dishes differed in morphology from those in the plastic dishes. They had abundant cytoplasm, well-developed Golgi complexes, and many microvillus-like cell protrusions. Moreover, they had hemidesmosome-like and desmosome-like structures on their surface and an increased amount of intracytoplasmic desmosome-like structures. The cells in clusters in the collagen-coated dishes were closely connected by junctional complexes, such as tight junctions, desmosomes and interdigitations, whereas those in plastic dishes were linked only by desmosomes. These results suggest that collagen affects the morphology of human scirrhous carcinoma cells.

Comparison of proteinase activities in squamous cell carcinoma, basal cell epithelioma, and seborrheic keratosis

The correlation between proteinase activities and invasive and metastatic potentials was investigated by comparing three different kinds of tumors. Extracts from tumor homogenate of 11 squamous cell carcinoma (SCC), 5 basal cell epithelioma (BCE), and 8 seborrheic keratosis (SK) were prepared in order to examine the activity of acid phosphatase and proteinases such as cathepsin B and D, type I and IV collagenase, and plasminogen activator (PA). There was no difference observed between acid phosphatase and cathepsin D activities among the three tumors. Cathepsin B and PA activities were slightly elevated in SCC. Type I collagenase activity of SCC was 9-fold higher than that of SK (p less than 0.01), and type IV collagenase was 3-fold higher per tissue DNA (p less than 0.05). Type I and IV collagenase of BCE were elevated per tissue protein but not elevated per tissue DNA. Correlation was found between the level of cell differentiation in SCC and the activities of cathepsin B, PA, and type I collagenase. Poorly differentiated SCC exhibited a tendency to have higher proteinase activities. Proteinases that showed high activities in malignant tumor homogenate may be related to the degradation of the surrounding cell matrix in addition to intracellular metabolism. Type I and IV collagenase, in cooperation with cathepsin B and PA, might play a major role in invading the dermal stroma and basement membrane.

The relationship of collagenolytic activity to stage of human colorectal carcinoma

Collagenolytic enzymes produced by tumor cells are believed to play a significant role in the destruction of surrounding normal tissue and, in certain experimental animal systems, the ability of tumor cells to degrade type-IV collagen (basement membrane collagen) correlates positively with those cells' metastatic capacity. We measured collagenolytic activity levels of extracts from freshly excised colorectal carcinoma tissues and of conditioned media from primary organ culture (total of 114 tissues from 53 patients) by using purified radiolabelled type-I (rat tail) and type-IV (mouse Engelbreth-Holm-Swarm [EHS] sarcoma) collagens. Both type-IV and type-I collagenolytic activity levels of extracts from tumor and adjacent mucosa ranged from less than 1 to 80 ng/hr/mg wet tissue, and no significant differences between mucosa and carcinoma tissues were observed. In conditioned media, the type-IV collagenolytic activity was low for normal mucosa and benign tumors and slightly higher for carcinoma than for mucosa. In 5 of 32 primary tumors, collagenolytic activity levels were 2-5 times higher than in the rest of the tumors and mucosal tissues. There were no significant differences in collagenolytic activity levels of conditioned media and tissue extract from colorectal carcinoma of different Dukes' stages. Deep and superficial areas of primary tumors released similar type-IV collagenolytic activity levels, suggesting that there was little intratumoral heterogeneity in the release of this enzyme.

Basement membrane formation by malignant mouse keratinocyte cell lines in organotypic culture and transplants: correlation with degree of morphologic differentiation

Six malignant C3H mouse epidermal cell lines (HEL-30, HEL-37, HELP I, HELP IV, HD II, H3L), with different capacities for epidermal differentiation, were analyzed for their organized growth behavior and basement membrane (BM) formation in organotypical cultures in vitro and after transplantation into syngeneic mice. Expression and deposition of five BM components (type IV collagen, laminin, bullous pemphigoid antigen, fibronectin, heparan sulfate proteoglycan) were determined on frozen sections by indirect immunofluorescence. Additionally, synthesis and secretion of BM components by the line HEL-30 (in submersed cultures) were identified by metabolic labeling and immunoprecipitation. Morphologic differentiation features and formation of a structured BM were studied by electron microscopy. All cell lines were tumorigenic and invasive but nevertheless able to synthesize BM constituents in vitro and in vivo, although pronounced variations in the expression and the polarity and continuity of deposition were found. Irrespective of the amount of BM components synthesized, none of the cell lines formed a structured BM in organotypical cultures in vitro. After transplantation the production of BM components was improved and the newly formed epithelia were separated from the mesenchyme by a structured BM. The formation of BM occurred whether the epithelial cells were in immediate contact with the mesenchyme or separated by a 1 to 2 mm thick native collagen gel. Deposition of BM constituents and formation of BM structures occurred both at the superficial epithelium and around invading cell cords. The studies clearly demonstrated that malignant epidermal cells maintain their capacity to synthesize BM components. The extent of production and the polarity of deposition of the constituents and the quality of BM formation were usually higher in well differentiated cell lines and obviously correlated well with their preserved degree of differentiation. Comparable to normal keratinocytes, formation of structured BM requires interaction with living mesenchyme but occurs independently of direct epidermal-mesenchymal contact.

Biological studies of ten human squamous carcinoma cell lines: an overview

Ten cell lines established from surgical specimens of human squamous carcinomas of the tongue and larynx have been investigated with respect to their motility, ultrastructure, karyotypes, certain biochemical features, interaction with normal epithelial and stromal elements and capacity to infiltrate three-dimensional organoid systems. All the cell lines have maintained several morphological and biochemical characteristics indicating a common origin, although the extent to which each line displays this heritage is variable. The phenotypes of each of the individual cell lines are, however, notably stable. Data are provided for epithelial surface markers (including epidermal growth factor, EGF) and for the synthesis and release of prostaglandins and proteases which may be involved in invasive mechanisms. Encounters between the cell lines and organoid substrata (embryonic chick heart spheroids, human amnion, chick chorioallantoic membrane) are described: the results indicate a scale of invasiveness ranging from lack of penetration to full-thickness infiltration by cells showing various distinctive growth patterns. Correlation between in vitro and in vivo findings is discussed, and it is suggested that the biological heterogeneity of the lines may reflect inherent properties of the original carcinoma cell populations which are more distinctly expressed in vitro.

Immunohistochemical localization of basement membrane type IV collagen in invasive and metastatic squamous carcinomas of the head and neck

The immunohistochemical localization of basement membrane type IV collagen was investigated with a mouse monoclonal antibody in major surgical resections from 25 patients with invasive squamous carcinomas of the head and neck. Irrespective of site, size or stage of the disease, the 16 primary invasive tumours were almost completely surrounded by a layer of type IV collagen. Focal abnormalities were regularly present, consisting of thickening and aggregation of type IV collagen together with attenuation and segmental loss. Similar changes were seen in metastatic squamous carcinomas in 36 cervical lymph nodes. It is suggested that the probable formation of a normal basement membrane protein by these squamous carcinomas indicates the preservation of a normal function of differentiating squamous epithelia. The results indicate that a major basement membrane component, type IV collagen, continues to co-exist with invasive and metastatic squamous carcinomas.

Transcapsular spread of metastatic squamous cell carcinoma from cervical lymph nodes

The incidence, extent, and selected clinicopathologic correlations of transcapsular spread from metastatic tumor in the cervical lymph nodes have been investigated in 210 specimens obtained by radical neck dissection from 203 patients with squamous cell carcinomas of the head and neck. Transcapsular spread was detected in 137 of 159 (86 percent) positive specimens, and classified as macroscopic in 74 (54 percent) and microscopic in 63 (46 percent). Macroscopic transcapsular spread was seen most frequently in association with large nodal masses more than 3 cm in diameter (48 of 70 specimens, 69 percent), but also occurred in some specimens with smaller lymph nodes less than 3 cm in diameter (26 of 67 specimens, 39 percent). Anatomic structures most commonly invaded in areas of neck dissection with macroscopic spread from nodal metastases were skeletal muscle (39 dissections) and the adventitial coat of the internal jugular vein (27 dissections). Macroscopic transcapsular infiltration was associated with a high incidence (44 percent) of recurrent tumor in the ipsilateral neck, particularly within 12 months of surgery. Microscopic transcapsular growth was associated with a lower incidence (25 percent) of recurrent tumor in the ipsilateral neck but the difference did not reach statistical significance. Similar recurrence figures (32 percent) were found in the minority of patients whose nodal disease was intracapsular at the time of neck dissection. More precise definition of the morphologic extent of transcapsular spread could be important in clarifying its clinicopathologic correlations.