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Michael B Morgan

Publications and source records attributed to Michael B Morgan.

50 records · Page 3Linked to original sources
PubMed2002

Characterizing stress gene expression in reef-building corals exposed to the mosquitoside dibrom.

We characterize two genes expressed in Acropora cervicornis upon exposure to 0.5 microg/l of dibrom, a pesticide used for mosquito control in the Florida Keys. Fragments of these genes were isolated, sequenced, and developed into chemiluminescent probes for Northern slot blots. Expression of target transcripts was detected in corals exposed to a variety of stressors including organophosphates, organochlorines, heavy metals, naphthalene, and temperature. Within the context of stressors examined, the D25 probe demonstrates toxicant and concentration specificity for organophosphates, whereas the D50 probe had broader specificity, detecting transcripts in corals exposed to dibrom, naphthalene, and temperature stress. After characterizing specificity in the lab, these probes were used on field samples taken from the Florida Keys. Both probes detected their targets in samples taken from the upper Florida Keys in August 2000. Preliminary search of sequence databases suggest similarity exists between D25 and a thioesterase.

Amino Acid Sequence↗
PubMed2002

Malignant peripheral nerve sheath tumor with perineurial differentiation: "malignant perineurioma".

BACKGROUND: Although benign tumors derived from the nerve sheath perineurial cell have been described from a variety of anatomic sites and are known to be a component of a number of benign neoplasms, malignant nerve sheath tumors of perineurial origin are exceedingly uncommon. METHODS: We report an unusual case of a 70-year-old male who presented with a rapidly growing mass of the left arm, subsequently shown to be a malignant nerve sheath tumor with perineurial differentiation. A brief microscopic differential diagnosis and review of the literature are discussed. RESULTS: Histologic sections show a partially circumscribed tumor of atypical spindle cells arranged in sweeping fascicles embedded in a myxoid matrix with focal whorling. Nuclear pleomorphism was evident among scattered typical and atypical mitotic figures (mean mitotic index of 7/10 high-power fields). The immunophenotypic profile consisted of only vimentin and epithelial membrane antigen (EMA) positivity, while antibodies to S-100, CD34, smooth muscle actin, and pankeratins were negative. Ultrastructural features included spindle cells with long cytoplasmic processes invested by interrupted basal lamina and pinocytotic vesicles, consistent with perineurial differentiation. CONCLUSIONS: While the histogenic source of the benign perineurioma, the perineurial cell has only rarely been described in conjunction with malignant tumors. All cases to date have shown EMA-positive and S-100-negative atypical spindled cells arranged in fascicles embedded in a myxoid matrix. In addition to immunohistochemistry, ultrastructural examination may be necessary to support the diagnosis. The diagnostic differential includes melanoma, spindle cell squamous cell carcinoma, atypical fibroxanthoma, leiomyosarcoma, and conventional malignant peripheral nerve sheath tumor, most commonly of Schwannian differentiation. Recognizing perineurial differentiation is important since few cases have been reported to date and the biological potential of these neoplasms is not known.

Aged↗
PubMed2002

Nanobacteria and calcinosis cutis.

BACKGROUND: The nanobacteria are a recently characterized group of extremely small bacteria capable of precipitating calcium salts implicated in the pathogenesis of urinary calculi and calcific atherosclerosis. The pathogenesis of calcinosis cutis and its significance in conjunction with a variety of unrelated scarring and pre-existing cutaneous entities are incompletely understood. METHODS: A series of cases, including basal cell carcinoma with dystrophic calcification, subepidermal calcified nodule, pilomatricoma, and tumoral calcinosis, were ultrastructurally examined for the presence of Nanobacteria sp. RESULTS: All cases, including three basal cell carcinomas, two subepidermal calcified nodules, three cases of pilomatricoma, and two cases of tumoral calcinosis, were negative for Nanobacteria. CONCLUSIONS: The dystrophic calcification that occurs in conjunction with the above entities does not likely involve a bacterial-induced etiology. The cause of these entities remains unknown.

Adolescent↗
PubMed2002

Rhabdomyomatous mesenchymal hamartoma: an unusual dermal entity with a report of two cases and a review of the literature.

BACKGROUND: Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare congenital lesion of the dermis and soft tissues consisting of a disordered and varied collection of mature adipose tissue, skeletal muscle, adnexal elements and nerve bundles. This entity exists under various names including striated muscle hamartoma, congenital midline hamartoma, and hamartoma of cutaneous adnexa and mesenchyme. Several published cases report the occurrence of RMH within the setting of other uncommon congenital abnormalities. METHODS: We report the clinical and pathologic features of two cases of rhabdomyomatous mesenchymal hamartoma. Patient 1 is a 71-year-old man who presented for removal of a nodule located on his temple that had been traumatized during a recent haircut. Patient 2 is a 4-month-old infant with amnion rupture sequence and rare craniofacial abnormalities including facial clefts, microphthalmia, bilateral colobomas, and a mobile fingerlike projection above the left medial canthus. RESULTS: Histological examination in both cases showed a deep dermal and subcutaneous fat collection of disorganized skeletal muscle fibers, adipose and neural tissue, and adnexal structures. Characteristically, the skeletal muscle approximated folliculosebaceous structures in a haphazard manner. CONCLUSIONS: RMH is a rare benign condition of the deep dermis and subcutaneous fat with only 22 cases existing in the English literature. To our knowledge, this is the first report of an elderly man presenting with RMH, presumptively present since birth. There was no evidence of cellular or malignant degeneration. While the etiology of RMH is unknown, possible explanations include aberrancy in the embryonic migration of mesodermally derived tissues or a genetic defect predisposing to the formation of hamartomas.

Abnormalities, Multiple↗
PubMed2002

Melanoma associated with pseudoepitheliomatous hyperplasia: a case series and investigation into the role of epidermal growth factor receptor.

BACKGROUND: Pseudoepitheliomatous hyperplasia (PEH) is a reactive epithelial proliferation that occurs in response to underlying infectious, inflammatory, and neoplastic conditions. The histologic features of PEH may simulate squamous cell carcinoma and may obscure an underlying malignant process. The association of PEH with benign melanocytic nevi is well described in the literature. However, reports documenting the association of PEH with melanoma are rare. METHODS: We examined the demographic and histologic features in 13 cases of melanoma in association with PEH. In addition, we evaluated the possible pathogenic role of epidermal growth factor receptor (EGFR) using immunohistochemical methods. RESULTS: In each case, histologic examination revealed epidermal hyperplasia with irregular cords of well-differentiated epithelial cells extending into the dermis and infiltrating the melanoma. Although overlap existed, two patterns of epidermal hyperplasia were noted. The majority of cases (69%) exhibited acanthosis, hyperkeratosis, papillomatosis, and irregular infiltrating epithelial cords with squamous eddies. The remaining cases demonstrated basaloid acanthosis, laminated orthokeratosis, and horn cysts. EGFR immunohistochemical studies revealed strong staining within the basal layer of the epithelium, with no discernible difference between the hyperplastic epithelium overlying the melanoma cells and adjacent normal skin. Immunostaining among the melanoma cells was absent to weak in each of the cases. All cases exhibited intense EGFR immunoreactivity in macrophages underlying the epidermal lesions. CONCLUSIONS: Melanoma is capable of presenting in a variety of histologic guises, including a pattern with PEH. The etiology of PEH, as rarely seen in conjunction with melanoma, unlikely involves EGFR and remains to be elucidated.

Adolescent↗
PubMed2002

Histomorphologic and immunophenotypic analysis of fibrofolliculomas and trichodiscomas in Birt-Hogg-Dube syndrome and sporadic disease.

BACKGROUND: Fibrofolliculomas and trichodiscomas are benign dermal neoplasms that likely derive from the mantle of the hair follicle and can occur sporadically or in association with Birt-Hogg-Dube syndrome (BHDS). Little is known about the pathogenesis and immunophenotypic properties of these entities. METHODS: We investigated the histomorphologic and immnophenotypic properties of 15 fibrofolliculomas and trichodiscomas in two patients with BHDS and eight with sporadic disease. RESULTS: We found the following: (1) fibrofolliculomas and trichodiscomas occurring in the setting of BHDS show microscopically contiguous histomorphologic features as compared to those occurring sporadically; (2) the immunophenotypic characteristics of syndromic-associated and sporadic types are identical and consist of (3) perifollicular vimentin (+), CD34 (+) and Factor XIII (-) spindle cells. CONCLUSIONS: Despite subtle histomorphologic differences, trichodiscomas and fibrofolliculomas are immunophenotypically similar, and are thus likely derived from a similar histogenic precursor. Given the previously reported CD34 (+) immunophenotype of the hair mantle, our findings would support an origin of these lesions from the mantle of the hair follicle. The proliferation of CD34 (+) spindle cells seen in conjunction with these lesions should not be confused with other CD34 (+) dermal entities.

Adult↗
PubMed2002

An investigation of apoptosis in androgenetic alopecia.

While the androgens, including dihydrotestosterone (DHT), have been implicated in the development of androgenetic alopecia (AGA), the exact mechanism by which they exert their effects is unknown. As apoptosis is an integral component of the normal cycling of human hair, we investigated individuals clinically affected by AGA to assess whether objective differences in the expression of apoptosis related immunohistochemical markers could be observed in scalp biopsies. Specimens from 13 alopecic male cadavers were stained with bcl-2 and terminal deoxynucleotidetransferase dUTP fluorescein nick end-labeling (TUNEL) methods to assess apoptotic activity in affected and unaffected areas of the scalp. Immunoreactivity was analyzed by quantifying nuclear staining differences within the same individual. Sections from two living human volunteers were obtained to establish the method validity. Significant differences in bcl-2 expression were observed between areas of the scalp clinically affected and unaffected by AGA. The Gaussian distribution of bcl-2 staining suggests that a relatively uniform population of follicles exists at the frontal hairline and/or synchrony of follicular cycling occurs in AGA. The apoptosis "hot spot" described by TUNEL staining in the bulge-isthmus region of the murine follicle is also identifiable in the human follicle.

Aged↗
PubMed2002

A case of acantholytic dermatosis and leukemia cutis: cause or effect?

Leukemia cutis is capable of presenting in a variety of clinical and histologic guises. We describe a 75-year-old man with a recent diagnosis of M0 acute myelogenous leukemia, who presented with multiple pruritic erythematous papules on his chest and back. Microscopically, the epidermis showed acrosyringeal-based acantholysis consistent with transient acantholytic dermatosis (TAD), associated with exocytosis of atypical hematolymphoid cells. In addition, the dermis showed a contiguous atypical hematolymphoid proliferation consistent with conventional leukemia cutis. To our knowledge, this is the first such case combining features of TAD with leukemia cutis. It remains to be determined whether the acantholysis occurred secondary to the leukemia cutis, was initiated by the migration of leukemic cells, or if the association is merely serendipitous.

Acantholysis↗
PubMed2002

Perplexing papules and plaques.

Dermatologic diseases are capable of presenting in a variety of clinical and pathologic guises. We present the clinicopathologic features of an unusual case misinterpreted initially as a dermal hypersensitivity reaction that was later deemed to be the cholesterol emboli syndrome. Salient histologic features of this case were the presence of numerous dermal eosinophils and the diagnostic finding of an intravascular cholesterol embolus. The presence of dermal eosinophilia should prompt a search for cholesterol emboli in the appropriate context.

Aged↗
PubMed2002

Oncocytic metaplasia occurring in a spectrum of melanocytic nevi.

Oncocytosis is defined as a metaplastic change characterized by the presence of cells with finely granular eosinophilic cytoplasm caused by the accumulation of mitochondria. Although this histologic feature can be found in normal tissues, it can also be seen pathologically as a degenerative phenomenon, where an accumulation of mitochondria is thought to compensate for an uncoupling of oxidative metabolism secondary to cellular aging. Oncocytic metaplasia can be observed in a variety of cutaneous lesions but, to our knowledge, has not been described in melanocytic nevi. We retrospectively reviewed 87 melanocytic nevi from 83 patients that showed significant oncocytic change. We obtained patient clinical history through surveys completed by the patients' physicians. Ultrastructural studies were performed on 4 representative nevi to confirm the presence of increased mitochondria. We prospectively reviewed 100 randomly selected nevi looking for oncocytic changes. We subsequently did not find any correlation with patient demographics or medical histories. Histologic evaluation showed granular eosinophilic cytoplasm in 75% or greater of lesional cells in two thirds of cases. This phenomenon occurred in all types of melanocytic nevi. Ultrastructural studies revealed melanocytes with numerous mitochondria in close apposition to melanosomes. Focal oncocytic change was identified prospectively in 38 of 100 randomly selected melanocytic nevi. We conclude that oncocytosis in melanocytic nevi is a relatively common and underrecognized phenomenon.

Adolescent↗
PubMed2002

Verrucous carcinoma arising within syringocystadenoma papilliferum.

Syringocystadenoma papilliferum (SP) commonly arises in conjunction with nevus sebaceous. Other less common lesions reported with SP include apocrine adenoma, condyloma acuminatum, hidradenoma papilliferum associated with hidrocystoma, poroma folliculare, and a single case ofverrucous carcinoma. We report the second case of verrucous carcinoma in conjunction with SP.

Adenoma, Sweat Gland↗
PubMedDate not supplied

Differential C-erbB-2 and VEGF expression following BCG immunotherapy in superficial papillary transitional cell carcinoma of the bladder.

Bacillus Calmette Guerin (BCG) is generally regarded as an effective immunotherapy for superficially invasive papillary transitional cell carcinoma of the bladder. The exact mechanism(s) which underlie its efficacy are unknown. As C-erbB-2 oncoprotein and vascular endothelial growth factor (VEGF) have been shown to be over-expressed in TCC of the bladder, it has been postulated that they may be important in its pathogenesis. The purpose of this study was to 1.) differentially evaluate the effect of BCG immunotherapy in treated and untreated cohorts on the immunohistochemical expression of C-erbB-2 and VEGF in formalin-fixed paraffin-embedded sections of superficial and superficially invasive (Stage Ta-T1) transitional cell carcinoma of the bladder. Immunolabeling intensity was assessed independently by two pathologists and reported as a mean labeling index. The results confirm previous studies that 1.) both c-erbB-2 and VEGF are over-expressed in these tumors MLI = 90.1 and 45.7 respectively, 2.) that VEGF is an early and sensitive indicator of TCC, and 3.) that BCG has a salutary effect on papillary TCC, 66% vs. 89% recurrence rate, P = .04. Our findings show that 1.) C-erbB-2 expression is decreased in patients tumors which show response to BCG (45.7 to 38.5), P = 0.15, 2.) that BCG administration has no effect on the expression of VEGF. While the decrement in c-erbB-2 immunostaining observed in those patients who received BCG contrasts with the increase in c-erbB-2 immunolabeling observed in patients who did not receive BCG, the differences were not statistically significant and could reflect tumor grade or stage regression associated with BCG therapy. However, this study suggests that BCG differentially influences the expression of C-erbB-2 and VEGF.

BCG Vaccine↗
PubMedDate not supplied

Caveolin expression in adult renal tumors.

Histopathological criteria are usually sufficient for the accurate distinction of benign form malignant renal tumors. A minority of cases however, poses a vexing diagnostic dilemma. Recent studies suggest that caveolin, a scaffolding cell membrane protein may prove helpful in predicting the behavior of these neoplasms. We analyzed a series of 40 renal tumors of which 7 were clear cell and 6 granular Renal Cell Carcinomas (RCC), 10 cases of Papillary Carcinoma (PCC), 4 cases of Chromophobe Renal cell carcinomas (CRCR), 11 cases of Oncocytomas (OC) and 2 cases of Collecting Duct Carcinomas (CDC). The distribution of immunoreactivity was analyzed by quantifying caveolin cell membrane staining in each case. There was a statistically significant difference in the expression of caveolin-1 between oncocytoma with a mean labeling index of 91.7 and the cases of malignant renal tumors with a mean labeling index of 26.9 for RCC, 24 for CDC, 21 for CRCR, and 19.2 for PCC. The results suggest an association between loss of caveolin expression among malignant renal tumors that might be useful in distinguishing oncocytoma from malignant renal tumors and possibly implicates this peptide in their pathogenesis.

Adenocarcinoma, Clear Cell↗