Mislocalization of SMN from the I-band and M-band in human skeletal myofibers in spinal muscular atrophy associates with primary structural alterations of the sarcomere.

Spinal muscular atrophy (SMA) is caused by a deletion or mutation of the survival motor neuron 1 (SMN1) gene. Reduced SMN levels lead to motor neuron degeneration and muscular atrophy. SMN protein localizes to the cytoplasm and Cajal bodies. Moreover, in myofibrils from Drosophila and mice, SMN is a sarcomeric protein localized to the Z-disc. Although SMN participates in multiple functions, including the biogenesis of spliceosomal small nuclear ribonucleoproteins, its role in the sarcomere is unclear. Here, we analyzed the sarcomeric organization of SMN in human control and type I SMA skeletal myofibers. In control sarcomeres, we demonstrate that human SMN is localized to the titin-positive M-band and actin-positive I-band, and to SMN-positive granules that flanked the Z-discs. Co-immunoprecipitation assays revealed that SMN interacts with the sarcomeric protein actin, α-actinin, titin, and profilin2. In the type I SMA muscle, SMN levels were reduced, and atrophic (denervated) and hypertrophic (nondenervated) myofibers coexisted. The hypertrophied myofibers, which are potential primary targets of SMN deficiency, exhibited sites of focal or segmental alterations of the actin cytoskeleton, where the SMN immunostaining pattern was altered. Moreover, SMN was relocalized to the Z-disc in overcontracted minisarcomeres from hypertrophic myofibers. We propose that SMN could have an integrating role in the molecular components of the sarcomere. Consequently, low SMN levels might impact the normal sarcomeric architecture, resulting in the disruption of myofibrils found in SMA muscle. This primary effect might be independent of the neurogenic myopathy produced by denervation and contribute to pathophysiology of the SMA myopathy.

Cellular Myxoma of the Vocal Cord: A Case Report and Review of the Literature.

Myxomas are rare in the vocal cords. A 69-year-old man was admitted with one-year history of progressive dysphonia. Laryngoscopy revealed a polypoid mass on the right vocal cord. The diagnosis was cellular myxoma. A review of the literature including the present case revealed eleven reported cases of myxoma. Ten cases were classic myxoma. To the best of our knowledge, cellular myxoma has not been previously reported in the vocal cord. Hypercellularity does not affect the behavior of cellular myxoma. However, its recognition is important to prevent confusion with the group of low-grade myxoid sarcomas. Cellular myxoma should be considered in the differential diagnosis of any vocal cord mass.

Reorganization of the nuclear compartments involved in transcription and RNA processing in myonuclei of type I spinal muscular atrophy.

Type I spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by the loss or mutation of the survival motor neuron 1 (SMN1) gene. The reduction in SMN protein levels in SMA leads to the degeneration of motor neurons and muscular atrophy. In this study, we analyzed the nuclear reorganization in human skeletal myofibers from a type I SMA patient carrying a deletion of exons 7 and 8 in the SMN1 gene and two SMN2 gene copies and showing reduced SMN protein levels in the muscle compared with those in control samples. The morphometric analysis of myofiber size revealed the coexistence of atrophic and hypertrophic myofibers in SMA samples. Compared with controls, both nuclear size and the nuclear shape factor were significantly reduced in SMA myonuclei. Nuclear reorganization in SMA myonuclei was characterized by extensive heterochromatinization, the aggregation of splicing factors in large interchromatin granule clusters, and nucleolar alterations with the accumulation of the granular component and a loss of fibrillar center/dense fibrillar component units. These nuclear alterations reflect a severe perturbation of global pre-mRNA transcription and splicing, as well as nucleolar dysfunction, in SMA myofibers. Moreover, the finding of similar nuclear reorganization in both atrophic and hypetrophic myofibers provides additional support that the SMN deficiency in SMA patients may primarily affect the skeletal myofibers.

Incidental, low-fat variant of spindle cell lipoma: a novel tumour of the small intestine.

A woman underwent surgical intervention for a carcinoma of the ovary. In the intervention, a submucosal nodule of the ileum was found. Pathological study revealed a spindle cell lipoma (SCL). This case revealed the presence of CD34-positive spindle and stellate cells with dendritic cytoplasmic prolongations, a feature shared with dendritic fibromyxolipoma. Fluorescence in in situ hybridisation analysis showed 13q14 heterozygous deletion. Spindle cell lipoma of the small intestine has not been previously reported. Spindle cell lipoma, although rare, should be included among the benign mesenchymal lesions of the small intestine. This report extends the range of locations in which this tumour is found to arise.

Histiocytoid cardiomyopathy and ventricular noncompaction presenting as sudden death in an adult male.

Histiocytoid/oncocytic cardiomyopathy (HCM) is a rare, distinctive arrhythmogenic disorder that presents as arrhythmia or sudden death in infants and children. Ventricular noncompaction (VNC) is a rare cardiomyopathy characterized by a thickened endocardial layer of noncompacted myocardium and a thin epicardial layer of compacted myocardium. Only six cases of the association of both cardiomyopathies have been reported previously in the literature. All these cases were in children. To the best of our knowledge, a case of HCM has not been described in the adult. We report the case of a 45-year-old man with an increased heart weight and involvement of both ventricles by HCM and VNC cardiomyopathy. Besides, multiple foci of myocardial disorganization were detected. He died suddenly while hiking. The association of both processes HCM and VNC was an unexpected finding at autopsy. The death was linked to functional abnormalities of the cardiac histiocytoid cells, and it was favored by a state of abnormal development of the heart.

Lymphocyte-rich capillary-cavernous hemangioma of the mitral valve: a case report and review of the literature.

Valvular hemangioma incidence is extremely low. In this report, we describe a 62-year-old man who presented with mild edema of the lower limbs. An echocardiogram revealed an incidental 1.3-cm diameter mass on the anterior mitral valve leaflet for which he underwent surgical resection and mitral valve replacement. Histopathological examination showed a lymphocyte-rich capillary-cavernous hemangioma. The exuberant lymphoid stroma is unusual for hemangioma and represents an undescribed pattern of cardiac hemangioma. Including the present report, only 13 cases of mitral valve hemangioma have been reported to date. Most patients are adult. Mitral hemangioma originates in the atrial aspect of the valve and involves more commonly the anterior leaflet. The average maximum diameter of the lesion is 1.7 (S.D.=0.75) cm. Pure cavernous hemangioma is the predominant type of mitral hemangioma. Most of them are described as pedunculated or polypoid. Surgical excision appears to be curative. Recurrences have not been reported. Lymphocyte-rich cardiac hemangioma represents a peculiar type of hemangioma which should be included in the differential diagnosis of other vascular lesions.

Incidental Melanocytic Nevi in Hemorrhoidectomy Specimens.

BACKGROUND: Benign melanocytic nevi (MN) of the anal canal are exceptional and require adequate differential diagnosis. There are no data on incidence of these lesions. Only a single case report of hemorrhoid with an MN has been reported. The necessity of routine pathologic evaluation of hemorrhoidectomy specimens has been questioned. MATERIAL AND METHODS: The authors undertook a retrospective histologic study of the hemorrhoidal tissue obtained in a series of 1918 consecutive hemorrhoidectomies performed between January 2004 and November 2012. RESULTS: Incidental hemorrhoidal MN were detected in 4 (0.21%) patients. The ratio observed was 1 nevus in 480 specimens. Lesions were intradermal or purely junctional in nature. There were no mitoses or architectural disorder. An intradermal nevus showed localized pagetoid melanocytes. The mean age of the patients was 56.5 years (range 47-73 years). The mean size of nevi was 5.86 mm (range 1.89-13.86 mm). All cases were present in external hemorrhoids. CONCLUSIONS: Although uncommonly, incidental MN can be observed in hemorrhoidal tissue. They may show features of flexural nevi and pagetoid melanocytes. Routine histopathological study of hemorrhoidectomy specimens would help to detect benign or malignant melanocytic tumors of the anal canal as these neoplasms can be easily missed clinically. Furthermore, this practice would allow early diagnosis of significant associated processes.

Mucin-secreting clear cell renal cell carcinoma. A rare variant of conventional renal cell carcinoma.

We report herein one case of conventional renal cell carcinoma (RCC) producing extensive extracellular mucinous secretion in a 71-year-old man. To the best of our knowledge, the presence of mucinous secretion in this tumor has not been documented. Mucin production, despite its low frequency, can be considered an additional feature of conventional RCC. Therefore, clear cell RCC should be added to the list of parenchymal renal tumors that can show significant mucin secretion; and it should be included in the inventory of morphologic variations of this tumor, which may cause diagnostic difficulties. It is of primary importance to distinguish mucin-secreting clear cell RCC from the metastasis of a mucin-secreting tumor to conventional RCC. Presence of mucin in a clear cell carcinoma does not exclude a renal origin.

Atypical fibroxanthoma developing on a pacemaker pocket mimicking a pyogenic granuloma.

Malignant tumors at the site of implantation of a pacemaker generator, although rare, have been reported in the literature. We present a case of an 89-year-old man with atypical fibroxanthoma in a pacemaker pocket. The device had been implanted for more than 4 years. An exophytic tumor had developed in this place and was clinically interpreted as a pyogenic granuloma. An excisional biopsy revealed the nature of the tumor. To our knowledge, the association of atypical fibroxanthoma arising from a pacemaker pocket has not been previously reported. A review of the literature has revealed four malignant soft tissue tumors previously reported at the pacemaker site. Routine examination in all patients with implanted pacemaker generators should be practiced at follow-up visits. This would allow an early diagnosis of a malignant associated neoplasm. Pathologists should become familiar with this type of devices and their potential neoplastic complications.

Simultaneous papillary fibroelastomas of the pulmonary and aortic valves.

Cardiac papillary fibroelastomas (PFEs) are uncommon valve tumors. Multiple PFEs at the same or different locations in the heart account for less than 10% of patients with PFE. We herein describe a case of an asymptomatic PFE of both pulmonary and aortic valves which was incidentally diagnosed by echocardiography in a 60-year-old woman. Both PFEs were removed surgically without valve replacement. To our knowledge, this combination of lesions has not been previously reported. Even though PFEs are classified as benign cardiac tumors, they can present serious complications, such as embolic episodes, mechanical obstruction or valvular dysfunction. Valve-sparing shave excision of the lesions can be readily accomplished in most instances with good long-term results. All surgically removed valvular lesions should be histopathologically examined to confirm the echocardiographic diagnosis.

Reorganization of Cajal bodies and nucleolar targeting of coilin in motor neurons of type I spinal muscular atrophy.

Type I spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by loss or mutations of the survival motor neuron 1 (SMN1) gene. The reduction in SMN protein levels in SMA leads to degeneration and death of motor neurons. In this study, we have analyzed the nuclear reorganization of Cajal bodies, PML bodies and nucleoli in type I SMA motor neurons with homozygous deletion of exons 7 and 8 of the SMN1 gene. Western blot analysis is is revealed a marked reduction of SMN levels compared to the control sample. Using a neuronal dissociation procedure to perform a careful immunocytochemical and quantitative analysis of nuclear bodies, we demonstrated a severe decrease in the mean number of Cajal bodies per neuron and in the proportion of motor neurons containing these structures in type I SMA. Moreover, most Cajal bodies fail to recruit SMN and spliceosomal snRNPs, but contain the proteasome activator PA28, a molecular marker associated with the cellular stress response. Neuronal stress in SMA motor neurons also increases PML body number. The existence of chromatolysis and eccentric nuclei in SMA motor neurons correlates with Cajal body disruption and nucleolar relocalization of coil in, a Cajal body marker. Our results indicate that the Cajal body is a pathophysiological target in type I SMA motor neurons. They also suggest the Cajal body-dependent dysfunction of snRNP biogenesis and, therefore, pre-mRNA splicing in these neurons seems to be an essential component for SMA pathogenesis.

Bilateral xanthogranulomatous orchitis in a tetraplegic patient.

Xanthogranulomatous orchitis (XGO) is a rare chronic inflammatory process characterized by destruction of tissue that is replaced by an outstanding cellular infiltrate of lipid-laden macrophages. To date, 20 cases of this process have been reported previously. We present herein the case of a 55-year-old man who had sustained complete tetraplegia at C-6 level and neuropathic bladder for 21 years. After repeated episodes of urinary tract infection, the patient developed a bilateral XGO and a right xanthogranulomatous epididymitis (XGE) that were treated with bilateral orchiepididymectomy. To our knowledge, a bilateral XGO has not yet been reported. Repeated episodes of high-pressure urinary reflux along the vas deferens during dyssynergic voiding possibly led to retrograde extension from the urinary tract by common urinary pathogens and development of bilateral XGO and right XGE. Since tissue destruction is a feature of this process, curative treatment required antibiotic therapy followed by bilateral excision of testes and epididymes.

Incidental detection of oncocytosis in a renal biopsy specimen for idiopathic nephrotic syndrome.

Oncocytosis (oncocytomatosis) is a rare condition characterized by the presence of innumerable oncocytic nodules in one or both kidneys, usually associated with the presence of a dominant nodule. An incidental detection of a renal tumor in a renal biopsy performed for the diagnosis of a medical disease of the kidney is exceptional. We report herein a case of a 58-year-old woman presenting with idiopathic nephrotic syndrome. Histological examination of the percutaneous renal core biopsy revealed a minimal-change glomerular lesion and oncocytosis. A contrast-enhanced abdominal CT scan showed two solid round masses, one in each kidney, measuring 1.5 and 2 cm. The nephrotic syndrome was responsive first to prednisone and finally to cyclosporine. Pathological study of both renal dominant masses confirmed that they were oncocytomas. As far as we are aware, renal oncocytosis incidentally discovered in a biopsy performed for the diagnosis of a medical disease of the kidney has not been reported.

Mucin-producing renal oncocytoma. An undescribed variant of oncocytoma.

We report here one case of renal oncocytoma producing focal extracellular mucinous secretion in a 47-year-old woman. To the best of our knowledge, the presence of mucinous secretion in this tumor has not yet been reported. Mucin production, despite its low frequency, can be considered an additional feature of renal oncocytoma. Therefore, oncocytoma should be added to the list of parenchymal renal tumors that can show significant mucin secretion, and it should be included in the inventory of morphologic variations of oncocytoma which may cause diagnostic difficulties.

Cutaneous plasmacytosis limited to the extremities in a white patient: an unusual clinical picture.

Cutaneous plasmacytosis is an uncommon disease characterized by a cutaneous polyclonal plasma cell infiltrate usually associated with polyclonal hypergammaglobulinemia. It has predominantly been found in Japanese patients and it is rare in white patients. Clinically, this condition manifests as multiple red to dark brown skin lesions that mainly are located on the trunk. We report the case of a 66-year-old white woman who presented with reddish brown to violaceous macules and plaques restricted to the extremities. The histopathologic findings, laboratory data, and systemic studies led us to the diagnosis of cutaneous plasmacytosis.