Objective: To investigate the clinicopathologic features, immunophenotype, pathological diagnosis and treatment of malignant mixed tumor (MMT). Methods: Clinical and pathological features including immunohistochemical phenotypes were analyzed in a case of MMT accompanied with eccrine porocarcinoma (EP) involving both hands, diagnosed definitely in January 2018 along with review of relevant literature. Results: A 64-year-old man presented with multiple rash on both hands for 4 years. Three lesions of 0.5 to 2.2 cm were removed for pathological evaluation. The pathological changes on little finger of left and right hands were MMT with EP, whereas that removed from the right ring finger was EP. MMT showed infiltrative growth with vascular wall invasion and consisted of epithelial (glandular or tube differentiation) and mesenchymal components (mucinous and/or cartilage stroma). The endothelial cells showed moderate to severe cytological atypia, nuclear pleomorphism and increased mitotic activity. The glandular component had histological characteristics of syringocarcinoma with moderately atypical chondrocytes but without myoepithelium. EP was composed of basal cells with visible vacuoles in cytoplasm and the presence of tubular and squamous differentiation, along with obvious atypia. Immunohistochemically cavosurface epithelium of glandular differentiation of MMT showed positivity for CK7, EMA and CD117. Myoepithelium showed S-100, CK5/6 and p63 positivity and stromal cells were positive for S-100. Differential diagnoses included metaplastic carcinoma, malignant myoepithelioma and atypical mixed tumor of skin. Conclusions MMT with EP is extremely rare.The diagnosis of MMT depends on the morphologic features. Immunohistochemical staining is helpful for differential diagnosis. Surgical excision with safety margins is the treatment of choice. Complementary radiotherapy and/or chemotherapy is still controversial. The clinical course of MMT is deemed unpredictable and long-term follow-up is necessary.

Background and purpose: Long non-coding RNA small nucleolar RNA host gene 5 (lncRNA SNHG5) plays a cancer-promoting role in many cancers, however its effect on colorectal cancer (CRC) and its regulatory mechanism are not clear. This study aimed to explore the mechanism of lncRNA SNHG5/miR-26a-5p/metadherin (MTDH) signal axis promoting metastasis of CRC. Methods: The data of The Cancer Genome Atlas (TCGA) database was analyzed, the abnormal expression of lncRNA in CRC was explored and analyzed the survival. Samples of CRC, paracancerous tissues and complete clinical data of patients who underwent surgical resection from October 2020 to October 2021 were collected. The expression levels of SNHG5 and miR-26a-5p in lncRNA were detected by real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR), and the expression level of MTDH was detected by immunohistochemistry. The relationship between the relative expression level of lncRNA SNHG5 in CRC and clinicopathological features and survival time was analyzed. The effects of lncRNA SNHG5 on the proliferation, migration and invasion of CRC cells were detected by cell counting kit-8 (CCK-8), clone formation, scratching assays, transwell test and in vivo xenotransplantation. The relationship between CRC cell metastasis, the expression level of epithelial-mesenchymal transition related molecules and lncRNA SNHG5 expression level by Western blot and immunohistochemical detection were explored. The physical interaction between SNHG5 and miR-26a-5p, MTDH and miR-26a-5p was studied by RNA pull-down test, double luciferase reporter gene detection and RNA co-immunoprecipitation. The functional relationship among the three was verified by CCK-8, EdU and transwell experiments. The effect of SNHG5, miR-26a-5p and MTDH expression on migration and invasion related molecules was analyzed by Western blot. Results: The results of TCGA database analysis showed that lncRNA SNHG5 was significantly upregulated in CRC. The results of RTFQ-PCR and immunohistochemistry showed that the levels of lncRNA SNHG5 and MTDH in CRC tissues were significantly upregulated (P＜0.05), the level of miR-26a-5p was decreased (P＜0.05), and the level of MTDH in samples with high expression of SNHG5 was also increased. The expression of lncRNA SNHG5 in CRC tissues with serosa and extraserosal invasion, distant metastasis, lymph node metastasis and TNM stage Ⅲ was significantly higher compared with subserosal invasion, no distant metastasis and lymph node metastasis and TNM stage Ⅰ-Ⅱ (P＜0.05). The results of survival analysis showed that the high expression of lncRNA SNHG5 was significantly correlated with overall survival rate (P＜0.05). Overexpression of lncRNA SNHG5 could enhance the proliferation, clone formation, migration and invasion of CRC cells, promote the growth and lung metastasis of transplanted tumor, increase the relative expression level of Ki-67 proliferation index and vimentin (P＜0.05), and decrease the relative expression level of E-cadherin (P＜0.05). However, the development of CRC cells was inhibited after inhibition of lncRNA SNHG5 expression. RNA pull-down test, double luciferase reporter gene detection and RNA co-immunoprecipitation confirmed the physical interaction between SNHG5 and miR-26a-5p, MTDH and miR-26a-5p. Upregulation of miR-26a-5p or downregulation of MTDH expression in lncRNA SNHG5 overexpressed cells partially reversed the effects of lncRNA SNHG5 on proliferation, migration, invasion and expression of related molecules in CRC cells. Conclusion: LncRNA SNHG5 is upregulated in CRC tissues and cells, and its high expression is related to tumor progression and poor survival. It can be used as a molecular sponge of miR-26a-5p to regulate the expression of MTDH to promote the proliferation and metastasis of SW620 cells.