Immunohistochemical studies of one typical and two atypical cases of molluscum contagiosum with anti-CD34 monoclonal antibodies showed a tightly enclosing fine vasculature around the lesional masses of the disease. The thin interstitial septa between the lobules of the molluscum lesions also contained abundant endothelium. An electron microscopic study of a pinched-off lesion of common molluscum contagiosum demonstrated that the tightly enclosing blood vessels lacked muscle layers, suggesting that they were capillaries, being a distance of several hundred nanometers from the basal cells of the molluscum mass. A 3D constructed image of the vasculature confirmed a network of the vessels. These tightly enclosing vascular networks around the lesions of molluscum contagiosum support the rapid growth of this disease.

In a case of metanephric adenoma of the kidney, many apical cytoplasmic blebs were found on the luminal surface of tumor cells. The tumor, measuring 15 mm in diameter, was found incidentally in the right kidney of a 40-year-old woman. It consisted of a dense proliferation of cuboidal cells forming small tubules of round or irregular shape. The apical portion of the cytoplasm of tumor cells exhibited club-shaped expansion or dome-like protrusion which was largely occupied by numerous free ribosomes. The neck portion of the protruded apical cytoplasm was constricted, and the apical cytoplasm appeared to have been "pinched-off" and shed into the lumen. The prominent formation of apical cytoplasmic blebs has, to our knowledge, not been documented in renal tumors except in angiomyoadenomatous tumors. Its pathological significance is unknown, but it most likely represents a response of tumor cells to some hypoxic or toxic cellular injuries.

Background: A case of peritoneal mesothelioma with an anaplastic lymphoma kinase (ALK) translocation was identified, and we conducted further studies to obtain diagnostic and therapeutic insights. We believe that this is the first report describing the cytology of this new tumor type. Case: A teenage woman was referred for severe pleural effusion. Enhanced computed tomography indicated an abdominal mass with ascites. Laparoscopy revealed tumor dissemination from the pelvis to the upper abdomen. Because a high-grade serous carcinoma was suspected, ascitic cytology and biopsy were performed. Cytologically, the tumor displayed characteristics of both adenocarcinoma and reactive or neoplastic mesothelial cells. After extensive pathological evaluation, the tumor was diagnosed as malignant peritoneal mesothelioma. To verify the diagnosis and aid in developing a therapeutic strategy, several companion diagnostics were tried. Surprisingly, the tumor was ALK-positive, and ALK recombination was confirmed by an ALK break-apart test. Retrospectively, cells and tissue specimens were stained with ALK intercalated antibody-enhanced polymer. Tumor cells were clearly distinguished from the nonneoplastic background. Recombination in ALK was reconfirmed by the National Cancer Center Japan, and the patient was enrolled in a clinical trial for alectinib. Conclusion: Companion diagnostics-based cytology may provide a useful means of monitoring and evaluating a molecular-targeted therapy.

Two cases of skull base chordoma (case 1, a 57-year-old woman; case 2, a 69-year-old woman) were investigated immunohistochemically and ultrastructurally. The tumors showed histopathological features typical of chondroid chordoma and contained both classical chordomatous and hyaline cartilaginous components. Tumor cells were immunoreactive for cytokeratin, vimentin, and S-100 protein, but negative for microtubule-associated protein 2 and class III beta-tubulin (tub-B3). Tumor cells of case 2 were immunoreactive for tau-protein and class II beta-tubulin (tub-B2), whereas those of case 1 were negative. Ultrastructurally, tumor cells in both cases showed the presence of abundant glycogen granules, well-developed intracellular organelles, and desmosome-like junctions. In case 2, several microtubules were closely packed and ran parallel or in random directions within the dilated cisterns of rough-surfaced endoplasmic reticulum (rough ER). "Microtubules within rough ER" has been described in several neoplasms, including classical and chondroid chordomas. Although previous reports documented the tub-B3 immunoreactivity in chordomas, our results suggested that, in our case 2, the predominant isoform of beta-tubulin in microtubules within rough ER was not tub-B3 but tub-B2.