We regard sialolipoma as a distinct variant of salivary gland lipoma that can occur in both the major and minor salivary glands. Superficial parotidectomy, or surgical resection in the case of palatal tumours, is an appropriate treatment for this benign tumour.

Dedifferentiated adenoid cystic carcinomas are a recently defined, rare variant of adenoid cystic carcinomas characterized histologically by two components: conventional low-grade adenoid cystic carcinoma and high-grade "dedifferentiated" carcinoma. We examined six cases and analyzed their clinicopathologic profiles, including immunohistochemical features and p53 gene alterations. The 6 patients (3 men and 3 women) had a mean age of 46.8 years (range, 34-70 y). The mean size of the tumors was 3.5 cm (range, 1.7-6 cm). The submandibular gland, maxillary sinus, and nasal cavity were involved in 2 cases each. Postoperatively, 5 patients had local recurrence and 5 developed metastatic disease. Five patients died of disease at a mean of 33.7 months after diagnosis (range, 6-69 mo), and one other was alive with disease at 60 months. Histologically, the conventional low-grade adenoid cystic carcinoma component of the tumors consisted of a mixture of cribriform and tubular patterns with scant solid areas. The high-grade dedifferentiated carcinoma component was either a poorly differentiated adenocarcinoma (4 cases) or undifferentiated carcinoma (2 cases). Three tumors were studied immunohistochemically. Myoepithelial markers were expressed in low-grade adenoid cystic carcinoma but not in the dedifferentiated component. In 2 cases, diffusely positive p53 immunoreactivity together with HER-2/neu overexpression was restricted to the dedifferentiated component. Loss of pRb expression was demonstrated only in the dedifferentiated component of the 1 other case. The Ki-67-labeling index was higher in the dedifferentiated component than in the low-grade adenoid cystic carcinoma component. Furthermore, molecular analysis of 2 cases demonstrated the loss of heterozygosity at p53 microsatellite loci, accompanied by p53 gene point mutation, only in the dedifferentiated carcinoma component of 1 case, which was positive for p53 immunostaining. These results indicate that dedifferentiated adenoid cystic carcinoma is a highly aggressive tumor. Because of frequent recurrence and metastasis, the clinical course is short, similar to that of adenoid cystic carcinomas with a predominant solid growth pattern. Limited evidence suggests that p53 abnormalities in combination with HER-2/neu overexpression or loss of pRb expression may have a role in dedifferentiation of adenoid cystic carcinoma.

Hybrid carcinomas of the salivary gland are a recently defined and rare tumor entity, consisting of two histologically distinct types of carcinoma within the same topographic area. In this study, we examined nine such cases, which mainly arose in the parotid gland (seven cases), with an additional one each from submandibular and lacrimal glands, and analyzed their clinicopathologic profiles, including immunohistochemical features and p53 gene alterations. The prevalence of hybrid carcinomas was 0.4% among the 1863 cases of parotid gland tumors in our series. The nine patients comprised five men and four women, ranging in age from 40 to 81 years (mean, 62 y). Tumor size ranged from 2 to 10 cm (mean, 4.2 cm). Of the seven patients who were followed up, two were alive with disease and five were alive with no evidence of disease, although the follow-up period was short. Three cases had cervical lymph nodal metastases. The combinations of carcinoma components in our hybrid carcinomas were as follows: epithelial-myoepithelial carcinoma and basal cell adenocarcinoma in two cases, epithelial-myoepithelial carcinoma and squamous cell carcinoma in one case, salivary duct carcinoma and adenoid cystic carcinoma in two cases, myoepithelial carcinoma and salivary duct carcinoma in one, acinic cell carcinoma and salivary duct carcinoma in one, and squamous cell carcinoma and salivary duct carcinoma in two. Although the proportion of each carcinoma component in a tumor mass varied from case to case, the minor component always represented >10% of the area. Differences in cellular composition were studied by immunohistochemistry and electron microscopy. The Ki-67-labeling index apparently differed between the two carcinoma elements in five cases. Diffusely positive p53 immunoreactivity was observed in four cases, restricted to the more aggressive component in each pair. Furthermore, p53 gene alteration analysis of these p53-positive cases revealed that all and three cases demonstrated loss of heterozygosity at p53 microsatellite loci and p53 gene point mutations, respectively, which were detected only in the p53-immunoreactive carcinoma component. Therefore, there is the possibility that such molecular-genetic events take an integral part for inducing the transformation from histologically lower to higher grade tumor during the hybrid carcinoma genesis of the salivary glands.

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Background. Although there have been a few reports dealing with the sarcomatous changes of intrahepatic cholangiocarcinoma, its clinicopathologic features as well as immunohistochemical nature remain obscure. Methods. Among 155 cases of intrahepatic cholangiocarcinoma, 7 cases of sarcomatous cholangiocarcinoma were chosen. Immunohistochemical studies using the avidin‐biotin‐peroxidase complex method were performed on these cases. Results. The tumor showed both mucin‐producing adenocarcinoma areas and sarcomatous areas, the latter being predominant in three cases and focal in the other four. All the sarcomatous areas consisted of atypical spindle cells arranged in sheets or bundles. Pleomorphic giant cells were observed in some sarcomatous components in five cases. Immunohistochemical staining for keratin and epithelial membrane antigen revealed apparent positivity in the sarcomatous components of five cases. The patients with these tumors showed aggressive intrahepatic spreading and widespread metastasis of the sarcomatous cells, and demonstrated poorer prognosis than those with ordinary cholangiocarcinoma, with one exception, a patient who remained disease‐free for 3 years after surgery. Conclusions. These findings favor the possible epithelial origin of sarcomatous cells. Radical operation would be necessary for patients with this special type of cholangiocarcinoma.