Takashi Saku

Salivary pleomorphic adenoma is histopathologically characterized by its colorful stroma with myxoid, chondroid, and hyaline appearances, due to enhanced biosynthesis of extracellular matrix (ECM) molecules and poor vascularity. Thus, pleomorphic adenoma cells embedded in the stroma typically survive under hypoxic conditions. We determined the expression kinetics of ECM molecules, such as perlecan and fibronectin (FN), under hypoxia in SM-AP1 cells which are duct epithelial differentiated cells, and in SM-AP4 cells, which are myoepithelial differentiated cells, cloned from pleomorphic adenoma of the parotid gland. We investigated hypoxia-inducible factor-1α (HIF-1α)-inducing pathways through a variety of ECM molecules in association with their cellular proliferation and migration. We observed that hypoxic conditions with elevated HIF-1α protein levels induced increased expression of perlecan and FN in SM-AP cells than in controls. Moreover, perlecan and FN knockdown reduced the proliferation of SM-AP1 and SM-AP4 cells under hypoxia. Further, SM-AP1 cell migration was enhanced by both perlecan and FN knockdown, whereas SM-AP4 cell migration was increased by perlecan knockdown and inhibited by fibronectin knockdown. The results indicated that pleomorphic adenoma cells can survive under hypoxic conditions by promoting cell proliferation via enhanced synthesis of ECM molecules. Overall, ECM molecules may be a new anti-tumor target under hypoxic conditions.

Background: We previously introduced the Five-Parameter System (FPS), which exclusively evaluates keratinized cellular findings, for use in cytology examinations of oral well-differentiated squamous cell carcinoma (SCC) and carcinoma in situ (CIS) specimens, as they occasionally lack nuclear atypia and can be challenging for categorization by The Bethesda System (TBS). This study was conducted to determine whether FPS parameters are detectable even in oral SCC/CIS specimens with apparent nuclear atypia. Summary: Oral cytology specimens were obtained together with biopsy tissue samples. They were obtained from 59 malignant (HSIL and SCC) and 29 not-definitely malignant (NILM to ASC-H) specimens diagnosed using TBS. Following re-confirmation of the original TBS categorization, the specimens were re-evaluated using FPS. One or more of the FPS parameters were noted in 69 of 70 malignant specimens examined, of which 11 had been diagnosed by TBS as not-definitely malignant. The remaining one malignant specimen was diagnosed as SCC with only TBS. FPS parameters #1 (concentric arrangement), #2 (large cell number), #3 (bizarre-shaped cells), #4 (keratoglobules), and #5 (uneven filamentous cytoplasm) were observed only in malignant cases, while none were revealed in not-definitely malignant specimens. Finally, TBS supplemented with FPS achieved sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 100%. Key Messages: FPS parameters are included in most examinations of oral cytology specimens. Thus, FPS is highly recommended for use in cytology examinations of oral SCC regardless of differentiation degree to confirm judgment based on TBS, a mandatory standard, as well as to cover its limitation of mainly evaluating nuclear atypia. FPS is considered to be an important diagnostic tool for oral cytology, especially in triage cases, which are challenging for TBS. Cytopathology should not be limited to only nuclear findings but be based on whole-cell morphology.

Although emergence of keratin 17 (K17) and reciprocal loss of K13 are immunohistochemical hallmarks for oral mucosal malignancy, we report here findings of K17-positive (+) speckles, possibly equivalent to Civatte bodies, in benign oral lichen planus. Sixty-two biopsy samples from oral lichen planus cases were subjected to immunohistochemical examinations to analyze the distribution as well as histopathogenesis of Civatte bodies. K17 was irregularly positive among oral lichen planus-affected epithelial cells, and K17-positive (+) filamentous structures were irregularly distributed within the cytoplasm in confocal images. K17+ speckles were identified as Civatte bodies, and they were mainly distributed in the interface between epithelial cells and lymphocytic infiltrates (type A, 52.8%), followed by distribution within the epithelial layer (type B, 24.7%) or within the lamina propria with lymphocytic infiltration (type C, 22.5%). Apoptotic figures were often engulfed by macrophages and clearly distinguished from Civatte bodies by the presence TUNEL signals. These results indicate that K17 is a sensitive immunohistochemical marker for Civatte bodies and useful for differential diagnosis of oral lichen planus from other oral mucosal lesions. Civatte bodies are generated from denucleation of K17+ epithelial cells during the process of cell death via dyskeratosis, which is possibly related to blood capillary collapse.

Background: The cytology of oral squamous cell carcinoma (SCC) is challenging because oral SCC cells tend to be well differentiated and lack nuclear atypia, often resulting in a false negative diagnosis. The purpose of this study was to establish practical cytological parameters specific to oral SCCs.Methods: We reviewed 123 cases of malignancy and 53 of non‐neoplastic lesions of the oral mucosa, which had been diagnosed using both cytology and histopathology specimens. From those, we selected 12 SCC and 4 CIS cases that had initially been categorized as NILM to ASC‐H with the Bethesda system, as well as 4 non‐neoplastic samples categorized as LSIL or ASC‐H as controls, and compared their characteristic findings. After careful examinations, we highlighted five cytological parameters, as described in Results. Those 20 cytology samples were then reevaluated by 4 independent examiners using the Bethesda system as well as the 5 parameters.Results: Five cytological features, (i) concentric arrangement of orangeophilic cells (indicating keratin pearls), (ii) large number of orangeophilic cells, (iii) bizarre‐shaped orangeophilic cells without nuclear atypia, (iv) keratoglobules, and (v) uneven filamentous cytoplasm, were found to be significant parameters. All malignant cases contained at least one of those parameters, while none were observed in the four non‐neoplastic cases with nuclear atypia. In reevaluations, the Bethesda system did not help the screeners distinguish oral SCCs from non‐neoplastic lesions, while use of the five parameters enabled them to make a diagnosis of SCC.Conclusion: Recognition of the present five parameters is useful for oral SCC cytology. Diagn. Cytopathol. 2017;45:406–417.

Expression of keratin (K) 13 is replaced with that of K17 when squamous cells of the oral mucosa transform from normal and dysplastic epithelia to carcinoma in situ (CIS) and squamous cell carcinoma (SCC). Since 14-3-3 sigma is functionally associated with K17, we examined possible relationships between expression of K17 and 14-3-3 sigma in oral CIS and SCC tissues by immunohistochemistry. We furthermore examined whether or not K17 expression or knockdown by small interfering RNA (siRNA) modulates the behavior of SCC cells in culture in terms of cell proliferation and migration. In tissue specimens of oral SCC and CIS, the pattern of cytoplasmic expression of 14-3-3 sigma and K17 was similar but neither was expressed in normal or dysplastic epithelia. Both proteins were demonstrated in the cytoplasm of control oral SCC ZK-1 cells, but expression of 14-3-3 sigma changed from cytoplasmic to nuclear upon knockdown of K17. In carcinoma cells, therefore, cytoplasmic localization of 14-3-3 sigma seems to accompany expression of K17. In K17-knockdown cells, proliferation was significantly suppressed at 4 days after seeding. In addition, the cell size of K17-knockdown cells was significantly smaller than that of control cells; as a result of which in the migration experiments, we found delayed closure of scratch wounds but migration as such was not affected. We conclude that K17 expression promotes SCC cell growth and cell size but does not affect cell migration. K17 expression is accompanied by cytoplasmic expression of 14-3-3 sigma, indicative of their functional relationship.