Diagnostic value of microtubule-associated protein-2 in Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is a rare, aggressive cutaneous carcinoma with neuroendocrine differentiation and a propensity for early spread to regional lymph nodes. Since surgical resection is the mainstay of treatment of MCC, differentiation of MCC from malignant lymphoma, metastatic small cell carcinoma, basal cell carcinoma, and malignant melanoma is very important and is sometimes challenging with routine histologic examination. Immunohistochemical studies may be required to differentiate MCC from other primary and metastatic skin neoplasms. Previously, the authors reported that microtubule-associated protein-2 (MAP-2) is a sensitive and specific marker for pulmonary neoplasms with neuroendocrine differentiation. Because MCC is also a neuroendocrine carcinoma, the authors hypothesized that MAP-2 may be expressed in MCC and therefore may be a useful marker in establishing an accurate diagnosis. MAP-2 staining was demonstrated in all 14 MCCs with diffuse (10 cases) to focal (4 cases) patterns of immunoreactivity. No MAP-2 immunoreactivity was observed in any lymphoma (14 cases), basal cell carcinoma (20 cases), or squamous cell carcinoma (14 cases). CK20 reactivity was present in 12 of 14 cases with focal (2 cases) to diffuse (10 cases) staining having the characteristic perinuclear dot-like pattern. NSE was positive in 13 of 14 cases, SYN was positive in all 14 cases, CHR was positive in 8 of 14 cases, CK7 was positive in 4 of 14 cases, and CD99 was focally positive in 2 cases and diffusely positive in 3 cases. MAP-2 showed a diffuse or focal staining of MCC with a +1 to +4 intensity in most cases. MAP-2 was positive in two cases of MCC that were negative for CK20 and CHR and negative or only slightly positive for SYN and NSE. Therefore, MAP-2 may be a valuable ancillary study in skin tumors suspicious for neuroendocrine origin with faint or negative staining with the antibodies traditionally used for diagnosing MCC. The authors believe this is the first study to demonstrate the utility of MAP-2 in the immunohistochemical workup of MCC. The authors recommend that MAP-2 be added to immunohistochemical panels to confirm the diagnosis of MCC.

Differentiation of immunostimulatory stem-cell- and monocyte-derived dendritic cells involves maturation of intracellular compartments responsible for antigen presentation and secretion.

Dendritic cells (DCs) are important for the induction of primary T-cell responses and may serve as "biologic adjuvants" in therapeutic protocols. However, given the "plasticity" of this antigen-presenting cell, it remains unclear which DC type (source, subtype, and stage of differentiation) should be applied clinically. To provide additional insight in this selection process, we have, for the first time, analyzed the in vitro differentiation of CD34(+) precursor-derived and monocyte-derived DCs for ultrastructure, phenotype, and function. The ultrastructural intracytoplasmic differentiation of DCs correlated with increasing T-cell stimulatory activity of these cells. "Early-stage"-DCs proliferate, exhibit high levels of soluble antigen uptake, and moderate T-cell stimulatory capacity, and are characterized by centrally located nuclei and numerous enlarged mitochondria. "Intermediate-stage"-DCs are enlarged cells with enhanced T-cell stimulatory activity and pronounced cytoplasmic protein synthesis machinery. "Late-stage" (LS)-DCs exhibit a mature secretory cell phenotype and low proliferative index. They express high levels of the HLA-DR, CD40L, B7-1, and B7-2 molecules and CD83, a specific marker of mature DCs, and appear maximally stimulatory to T cells. Ultrastructurally, LS-DCs feature an accentric nucleus, an enlarged cytoplasm, containing numerous secretory storage vesicles, along with a fully developed Golgi complex. LS-DCs exhibited numerous multivesicular and multilaminar structures containing major histocompatibility complex class II molecules, consistent with the MIIC (peptide-loading) compartment. In extended studies, cultured CD14(+) monocyte-derived DCs displayed a similar, but accelerated, temporal differentiation staging pattern.

Clinicopathologic evaluation of the Mueller muscle in thyroid-associated orbitopathy.

PURPOSE: To study the histopathologic features of the Mueller muscle in chronic eyelid retraction caused by thyroid-associated orbitopathy. To investigate if the degree of eyelid retraction correlates with any histopathologic finding. METHODS: A prospective case series of 23 consecutive patients with thyroid-associated orbitopathy was studied. Specimens were obtained during a standard muellerectomy. Formalin-preserved specimens were studied with the use of hematoxylin-eosin, periodic acid-Schiff, Masson trichrome, and Giemsa stains. Immunostaining against leukocyte common antigen, L26, CD3, and KP-1 was performed. Three control specimens were also evaluated in a similar fashion. Fresh tissue was placed in cold glutaraldehyde overnight, postfixed, dehydrated, and infiltrated with epoxy resin. Silver (70 nm) sections were cut and stained with uranyl acetate and lead citrate for electron microscopic examination. RESULTS: On light microscopy, fibrosis and mast cell infiltration was present in all 23 specimens. Fat infiltration was noted in 16 of 23 specimens and did not correlate with increasing age of the patient. Interstitial edema and lymphocytic infiltration were not observed. On immunohistochemistry, leukocyte common antigen was positive, confirming the presence of inflammation. L26, CD3, and KP1 were negative. Electron microscopy demonstrated fibrosis, mast cells, and abundant contracting Mueller cells. The degree of clinical retraction in millimeters did not correlate with fibrosis, inflammation, or fat infiltration. The control specimens demonstrated rare fat and mast cell infiltration and no fibrosis. CONCLUSIONS: Contrary to previous reports, the Mueller muscle is involved in the inflammation and fibrosis that characterizes thyroid-associated orbitopathy. The Mueller muscle is grossly enlarged. On histopathologic inspection, fibrosis, fatty infiltration, and increased mast cell presence accompany focal atrophy of the Mueller muscle. In concordance with prior descriptions, many Mueller cells are in an actively contracting state on electron microscopy.

Force Modulation Elasticity Mapping of Plastic-embedded, Thin-sectioned Skeletal Muscle.

We have been researching the capability of atomic force microscopy to reveal nontopographic properties of tissue embedded in plastic and sectioned with standard electron microscopic techniques. We present topography and elasticity maps of plastic-embedded, thin sections of muscle tissue. The images show topography correlated with the normal repeating structure of the sarcomere. Elasticity mapping using force modulation revealed contrast between the actin- and myosin-rich areas. We attribute the observed contrast in elasticity to the difference in local concentrations of biological material in embedding plastic.