On examination of the thyroid glands in 408 consecutive autopsy cases, 64 occult papillary carcinomas (OPC) were found in 46 cases (11.3%) whose age ranged from 16 to 82 years. Their incidence was 26 of 247 (10.5%) in male and 20/161 (12.4%) in female cases. No definite correlation was found between the incidence of carcinoma and sex or age. All 64 carcinomas were less than 7.7 mm in diameter. They exhibited nuclear characteristics of papillary carcinoma although their growth patterns were "follicular" in the tumors less than 1 mm, and "papillary" in 70% of the tumors more than 3 mm in diameter. The carcinomas were classified into three types according to the presence or absence of capsular formation and fibrosis: encapsulated tumors (ET), nonencapsulated sclerosing tumors (NEST), and nonsclerosing tumors (NST). The NEST (28 tumors) and NST (26 tumors) were found in persons of all ages, whereas ET (ten tumors) were found only in those of older than 53 years. The mean tumor diameters of the three types, 4.57 mm for ET, 2.10 mm for NEST, and 0.85 mm for NST, were significantly different. These findings suggested that papillary carcinomas arose as minute carcinomas showing follicular pattern at any age as NST and then changed to NEST and ET, and papillary pattern became prominent if the tumors continued to grow. Very minute carcinomas were detected in serial sections of two of 27 fibrosclerotic nodules. Occult papillary carcinomas were found at significantly high incidence in cases with adenomatous goiter.

A primary hepatic marginal zone B cell lymphoma of mucosa-associated lymphoid tissue (MALT) is very rare. We found a solitary mass 27 mm in size in the left lobe of the liver of a 58-year-old Japanese man with a history of hepatitis-C infection. Based on the results of imaging studies, the tumor was diagnosed as a hepatocellular carcinoma (HCC). The left lobe of the liver was lobectomized and microscopic findings showed that the tumor was a hepatic MALT lymphoma, while immunohistochemistry showed it to be positive for CD20 and CD79a. In a fluorodeoxyglucose-positron emission tomography examination integrated with computed tomography scanning (FDG-PET CT) before surgery, the tumor was revealed to have a high standardized uptake value (SUV) for FDG. The patient received chemotherapy after surgery. To the best of our knowledge, 45 cases had been reported with a mean age for all patients of 61.4 years. The pathogenesis remains unclear, although half of the patients had a past history of chronic inflammatory liver disease. Surgical resection was performed in most cases and some patients received postoperative chemotherapy or radiotherapy. The clinicopathologic characteristics and management of this extremely rare disease are also discussed.

The dose dependencies of the lung carcinogenicity of 1,6-dinitropyrene (1,6-DNP) and benzo[a]pyrene (BaP) were examined by direct injections of these compounds into rat lungs. A total of 276 male F344 rats were divided into 10 groups and given various doses of 1,6-DNP or BaP, or no drug (control group). Both chemicals were injected into the lung, as suspensions in beeswax--tricaprylin and the animals were then observed for 104 weeks. The incidences of lung cancer were 0/39 (0%), 4/30 (13%), 13/31 (42%), 22/26 (85%) and 6/9 (67%) in groups treated with 0.003, 0.01, 0.03, 0.1 and 0.15 mg of 1,6-DNP respectively, and 1/29 (3%), 7/30 (23%), 22/29 (76%) and 9/13 (69%) in those treated with 0.03, 0.1, 0.3 and 1.0 mg of BaP respectively. No lung cancer was found in control rats. Thus the incidences of lung cancer induced by 1,6-DNP and BaP showed significant dose dependence. At equal doses, the incidence of lung cancer was much higher with 1,6-DNP than with BaP, and the induction of cancer by 1,6-DNP was higher even at one-third the dose of BaP. Histologically, most tumors induced by 1,6-DNP were undifferentiated neoplasms, whereas most of those induced by BaP were well-differentiated squamous cell carcinomas.

A 59-year-old man was admitted to our hospital with dyspnea and cough. A large polypoid tumor was observed in the lower trachea and bronchoscopic polypectomy was performed using a snare to relieve symptoms. The tumor was diagnosed as a high grade mucoepidermoid carcinoma mainly by the histology of piecemeal specimens obtained by bronchoscopic resection. The primary lesion involved the trachea and the main bronchus, and there were multiple metastases in the lung. The patient was treated with the combination of carboplatin and paclitaxel. After four cycles of chemotherapy, the tumors were significantly reduced. He remains well without evidence of tumor progression for 25 months. This case suggests that the combination chemotherapy of carboplatin and paclitaxel can be an option for treatment of pulmonary mucoepidermoid carcinoma.

Visual assessment of Ki67 by a 5-grade scale (Eye-5) is fast, easy, and reliable with acceptably low interobserver and intraobserver variability. Eye-5 can replace LI in many luminal tumours, and is a strong candidate as a standard method of evaluating Ki67.