Andrew J. Hanly

Analysis of thyroid transcription factor-1 and cytokeratin 20 separates merkel cell carcinoma from small cell carcinoma of lung

Merkel cell carcinoma needs to be separated from small cell carcinoma metastatic from visceral sites to skin. Pulmonary small cell carcinoma is the most common primary site of small cell carcinoma. We evaluated the immunophenotypic characteristics of 21 Merkel cell carcinomas and 33 small cell carcinomas of lung using thyroid transcription factor‐1 and cytokeratin 20. Thyroid transcription factor‐1 was 100% specific for the diagnosis of small cell carcinoma of lung associated with a diagnostic sensitivity of 85%. Cytokeratin 20 was present in 95% of Merkel cell carcinomas; however, 33% of small cell carcinoma of lung were also positive. Both antibodies typically demonstrate diffuse and intense staining of their respective tumor cells. We conclude that thyroid transcription factor‐1 is a sensitive and specific marker for small cell carcinomas of lung and that a combination of thyroid transcription factor‐1 and cytokeratin 20 is indicated to assist in the differentiation of metastatic small cell carcinoma of lung from merkel cell carcinoma.

HLA-DR-positive dendritic cells of the normal human choroid plexus: A potential reservoir of HIV in the central nervous system☆

In a previous study of choroid plexus (CPx) from patients with the acquired immunodeficiency syndrome (AIDS), we found a population of stromal cells infected with the human immunodeficiency virus (HIV). To determine whether these represented antigen-presenting dendritic cells, we examined the phenotype of normal human choroid plexus by light and electron microscopy (EM) and established the HIV-infected cell type by immunohistochemistry in AIDS cases with HIV-infected CPx. Monoclonal antibodies were used to detect class II major histocompatibility antigens (MHC), S-100 and S-100beta protein, lymphocytes, monocytes/macrophages, and HIV glycoprotein. A variable number of stromal cells had slightly elongated nuclei and long branching processes that were strongly immunoreactive for class II MHCs, rarely reactive for S-100 and S-100beta and immunonegative for monocyte/macrophage markers. Phagocytic activity was absent by EM and immunomarkers. They were numerous in the subepithelial region, and their processes occasionally extended toward the stromal capillaries or between the CPx epithelial cells. The HIV-infected cells were intensely immunoreactive for class II MHC markers and often displayed a dendritic morphology. These results document the presence of dendritic cells in the normal human CPx whose morphology and immunophenotype closely resemble those of DCs elsewhere in the body. They also show that these immunoreactive MHC class II cells are the cell type infected by HIV. We suggest that the functional activity of the CPx DCs is similar to that of antigen-presenting dendritic cells elsewhere in the body. This includes the potential to harbor HIV during the prolonged period of clinical latency, acting as a central nervous system reservoir of infection before the onset of AIDS.

Discrimination of late apoptotic/necrotic cells (type III) by flow cytometry in solid tumors

A method is described for the discrimination of Type III, late apoptotic, and necrotic cells, to improve the accuracy of proliferation and ploidy determinations of breast tumors. We selected an immunological probe, antitubulin antibody, and a DNA specific stain, propidium iodide (PI), both capable of crossing the permeable membranes of Type III, late apoptotic, and necrotic cells. This study utilized MDA-MB-175-VII breast carcinoma cells deprived of oxygen for up to 11 d to simulate intratumoral hypoxia, and 10 human breast tumors and mouse-human breast tumor xenografts disassociated by mechanical or enzymatic means. After 24 h under hypoxic conditions, the MDA cells displayed characteristics associated with both apoptosis and necrosis. Approximately 50% of day 1 cells showed membrane permeability by trypan blue and absence of DNA laddering; however, by day 3-4 characteristic apoptotic DNA laddering by gel electrophoresis was evident. Substantial DNA content loss, further evidenced by a reduction in PI staining and fluorescent microscopy, was obvious by day 5. By day 10, 98% of cells showed no propidium iodide staining by conventional PI live/dead cell gating, but were positive for antitubulin antibody staining. When the study was extended to the analysis of ten tumors, antitubulin antibody showed a range of 78%-96% staining with a median value of 87.5%, while PI staining showed a range of 8%-74% with a median value of 11.5%. This study demonstrates that a large percentage of cells in tumors and hypoxic cell populations have significantly reduced DNA content, such that conventional live/dead cell gating using PI may include many Type III cells as live cells, thus significantly altering data involving multicolor investigations.

Bednar tumor (pigmented dermatofibrosarcoma protuberans) occurring in a site of prior immunization: Immunochemical findings and therapy

Bednar tumor is a rare pigmented variant of dermatofibrosarcoma protuberans (DFSP). Because of its rarity, information is lacking regarding the optimal therapy and potential utility of immunohistochemistry in diagnosis. We report a case of Bednar tumor in which the diagnosis was aided by immunohistochemistry for CD34, an antigen known to be expressed in DFSP but not previously reported in Bednar tumor. Our case was also striking because it represents the first reported appearance of a Bednar tumor at a site of prior immunization, a phenomenon previously noted in some cases of DFSP. The patient was treated effectively with Mohs surgery and is without recurrence at 9 months.

Low Nuclear Proliferative Activity Is Associated With Nonmetastatic Islet Cell Tumors

CONTEXT Traditional morphologic features of tumor aggression are of limited value in predicting the malignant behavior of endocrine neoplasms. We explored the potential value of nuclear proliferative activity (using Ki-67 immunostaining with semiquantitative scoring) in predicting the clinical behavior of pancreatic islet cell tumors (ICTs), and we correlated this characteristic with hormone expression. OBJECTIVE To evaluate whether Ki-67 immunostaining using a semiquantitative scoring system has value in predicting the clinical behavior of pancreatic ICTs. DESIGN We studied 39 pancreatic ICTs from 39 patients. Twenty-two ICTs did not metastasize in a median follow-up period of 91 months. The remaining 17 neoplasms did produce metastases (8 in liver, 7 in regional lymph nodes, and 2 in peritoneum). Immunohistochemistry was performed using antibodies to Ki-67 and pancreatic hormones (insulin, glucagon, gastrin, somatostatin, pancreatic polypeptide, vasoactive intestinal polypeptide, and corticotropin). A semiquantitative Ki-67 grading system was followed. The nuclear proliferative activity, as determined by a positive reaction for Ki-67, was considered low (<5% of cells staining positively), intermediate (5%-25% of cells staining positively), or high (>25% of cells staining positively). RESULTS The majority of the nonmetastatic ICTs (16 cases, 73%) demonstrated either negative or low staining for Ki-67 (P <.001). Conversely, all metastatic ICTs expressed at least an intermediate-grade reaction. High nuclear proliferative activity was only seen in metastatic neoplasms (3 cases, 17%). There was no relationship between immunoexpression of pancreatic hormones and nuclear proliferative activity by either group of tumors. CONCLUSION An ICT with low nuclear proliferative activity is unlikely to metastasize, whereas high proliferative activity is associated with a metastatic phenotype. Immunohistochemical assessment of Ki-67 using a semiquantitative scoring system is a simple and reliable detection method of cellular proliferative activity in ICTs of the pancreas.

High Proliferative Activity Excludes Dermatofibroma: Report of the Utility of MIB-1 in the Differential Diagnosis of Selected Fibrohistiocytic Tumors

CONTEXT Dermatofibroma is a benign fibrohistiocytic tumor composed of a mixture of fibroblastic and histiocytic cells. The diagnosis of this tumor is generally uncomplicated; however, rare variants may be difficult to distinguish from malignant fibrohistiocytic tumors. Deep penetrating dermatofibroma may be difficult to distinguish from dermatofibrosarcoma protuberans, and pseudosarcomatous dermatofibroma and dermatofibroma with monster giant cells share morphologic similarities with malignant fibrous histiocytoma and atypical fibroxanthoma. OBJECTIVE To find an immunohistochemical marker or markers that differentiate between fibrohistiocytic lesions of skin. DESIGN We evaluated the immunophenotypic characteristics of 83 fibrohistiocytic tumors (36 typical dermatofibromas, 16 cases of dermatofibrosarcoma protuberans, 16 malignant fibrous histiocytomas, and 15 atypical fibroxanthomas) using antibodies against MIB-1 (Ki-67), factor XIIIa, CD34 (HPCA-1), HHF35 (muscle-specific actin), 1A4 (smooth muscle actin), cytokeratin (AE1/AE3, CAM 5.2, and 34betaE12), S100 protein, and desmin. RESULTS A high proliferative index detected by MIB-1 staining excluded the possibility of dermatofibroma and was diagnostically useful in separating this entity from dermatofibrosarcoma protuberans, malignant fibrous histiocytoma, and atypical fibroxanthoma. A low proliferative index, however, could not differentiate dermatofibroma from dermatofibrosarcoma protuberans. Factor XIIIa reactivity was not helpful for the diagnosis of dermatofibroma, whereas CD34 reactivity was statistically significant in the diagnosis of dermatofibrosarcoma protuberans. The sensitivity of these 2 markers is low and therefore of questionable practical diagnostic value. CONCLUSION Evaluation of the proliferative index may further assist in distinguishing dermatofibroma from dermatofibrosarcoma protuberans, atypical fibroxanthoma, and malignant fibrous histiocytoma.

Interleukin 11 reduces apoptosis in UVB-irradiated mouse skin.

Background: UVB radiation, the major cause of skin cancer, causes apoptosis in the skin, characterized by the appearance of ‘sunburn cells’. Interleukin 11 (IL-11) has been shown to protect cells in the gastrointestinal system from chemotherapy and radiation-induced death. Objective: To determine whether exogenous IL-11 has any effect on the UVB-induced apoptosis of cutaneous tissues. Methods: Mice were injected with IL-11 or vehicle control prior to irradiation, and TUNEL assays were performed on paraffin-embedded tissue sections at various times after irradiation. Results: Exogenous IL-11 protects epidermal keratinocytes, epithelial cells of the hair follicles inflammatory cells and fibroblasts in the dermis from UVB-induced apoptotic death. Conclusion: These findings suggest that IL-11 may play a role in the general homeostasis of the skin.

Mucocutaneous pigmented macule as a result of zinc deposition

Background:  Mucocutaneous depositions of various metals such as silver, lead, gold, arsenic, mercury, iron, and bismuth have been previously published. Heavy metal deposition typically occurs in the setting of either prolonged topical application to intact skin, topical application to eroded or ulcerated skin, as a result of either parenteral administration, or due to penetrating traumatic exposure.