OBJECTIVE: There are two main subtypes of mucinous carcinoma (MC) based on the quantification of the mucinous component: the pure variant (pMC) and the mixed variant (mMC). pMC has been subdivided into pure A with a hypocellular variant, and pure B with a hypercellular variant.
METHODS: We retrospectively analyzed the clinicopathological features of 99 patients with MC who were treated at our institution from January 2002 to December 2014. We evaluated the expression profiles of markers, including mucin (MUC) family members, in the patients groups representing different MC subtypes by performing immunohistochemistry to identify factors involved in the differentiation and progression of MCs.
RESULTS: Among the 99 patients, 76 (76.8%) had pure mucinous carcinomas (pMC) and the other 23 (23.2%) had mixed mucinous carcinomas (mMC). Of the pMCs, 54 were pure A and 22 were pure B. The prognosis was worse for pure B than pure A and worse for mMC than pMC. Although there was no significant difference in clinicopathological factors between the pure A and pure B groups, immunohistochemical staining revealed differences in the localization of mucin MUC1 and β-catenin. A comparison of the pMC and mMC cases revealed more lymphovascular invasion in mMC and differences in the localization of β-catenin between the two groups.
CONCLUSIONS: The patients\' prognoses were significantly poorer depending on the histologic subtype (in the order pure A, pure B, and mixed). MUC1 localization and β-catenin were revealed as independent predictors contributing to the poorer prognosis.

Loss of the NF1 allele, coding for the protein neurofibromin, and polymorphism in the proto-oncogene RET (RETp) are purportedly common in desmoplastic melanoma (DM). DM is categorized into pure (PDM) and mixed (MDM) subtypes, which differ in prognosis. Most NF1 mutations result in a truncated/absent protein, making immunohistochemical screening for neurofibromin an ideal surrogate for NF1 allelic loss. Using antineurofibromin, our aims were to ascertain the incidence of neurofibromin loss in DM subtypes and to evaluate the relationship with RET, perineural invasion (PNI) and established histopathologic prognosticators. A total of 78 archival samples of DM met criteria for inclusion (54 cases of non-DM serving as controls). Immunohistochemistry was performed for neurofibromin, whereas direct DNA sequencing was used for RETp and BRAF mutation status. Statistical analyses included χ(2) test as well as Fisher exact test. Neurofibromin loss was more common in DM than non-DM (69% versus 54%; P=.02). In DM, significant differences in neurofibromin loss were noted in the following: non-head and neck versus head and neck biopsy site (88% versus 55%) and PDM versus MDM variants (80% versus 56%). No significant associations were noted with sex, presence of a junctional component, Breslow depth, ulceration, mitoses, host response, RETp, BRAF status, or PNI. RETp was marginally associated with PNI-positive DM versus PNI-negative DM (36 versus 18%; P=.08). Our findings, the largest to date investigating neurofibromin in DM, validate the incidence of NF1 mutations/allelic loss in DM and suggest that the DM subtypes have distinct genetic drivers.