Thin Fibrous Septa Research Articles

Clinical and pathologic features of tubulocystic carcinoma of kidney

To investigate clinicopathological features and differential diagnosis of tubulocystic carcinoma of the kidney. The clinical features, histological and immunohistochemical findings were analyzed in 3 cases of tubulocystic carcinoma of the kidney, along with review of the related literatures. Three patients were males with a mean age of 59 years old (range from 44 to 71 years). All presented with no symptom and their tumors were found during routine examination. The tumor size ranged from 1.5 to 5.0 cm in greatest dimension. The tumors were grossly well-circumscribed without capsules and exhibited a spongy cut surface. Microscopically, all three tumors were composed of tubules and cysts of varying sizes separated by thin fibrous septa. The epithelial lining cells were flat, cuboidal and columnar, with often a hobnail-like appearance characterized by abundant eosinophilic cytoplasm with prominent nucleoli. Two cases showed focal clear cytoplasm. One of the three cases coexisted with a papillary renal cell carcinoma. Immunohistochemically, all 3 cases showed positivity for pan-CK, vimentin, CK19, CD10, P504S, and focal positivity for 34βE12. Two cases showed focal positivity for CK7. Tubulocystic carcinoma of the kidney is a rare kidney neoplasm and occurs predominantly in males. The tumor is characterized by gross spongy appearance and microscopic cysts and tubules often lined by hobnail-like cells and separated by thin fibrotic stroma. The differential diagnosis mainly includes other lesions of the kidney that have a multicystic growth pattern.

Dermoscopy and Confocal Microscopy of Thrombosed Hemangiomas

O N CLINICAL EXAMINATION, THROMBOSED hemangiomas (THs) are sometimes difficult to differentiate from melanoma. The Figure, A and C, shows the worrisome clinical presentation of 2 cases appearing as irregularly pigmented nodules of recent onset, located on the right leg of a 48-year-old woman (Figure, A and B) and on the back of a 28-year-old woman (Figure, C and D). Dermoscopy showed a sharply demarcated, uniform, jet-black area (Figure, B and D), corresponding to the thrombus and red (Figure, B) to blue (Figure, D) lagoons, which led to the diagnosis of TH. In vivo reflectance confocal microscopy (RCM) documentation of vascular changes in skin tumors has been shown to be an important aspect of the microscopic evaluation. In our cases, RCM showed focal disruption and scaling of the cornified layer (Figure, E) and numerous dilated dark spaces (Figure, G and H [asterisks]), which were large in diameter and separated by thin fibrous septa (Figure, G and H [arrows]), corresponding to ectatic vessels below the dermoepidermal junction (Figure, F and I). Highly refractile round structures corresponding to blood cells can be visualized at higher magnification (Figure, J [arrowheads]). Blood flow was visible during in vivo imaging within the dark spaces (Video, http://www.archdermatol .com). The dilated dark spaces seen on RCM examination nicely correlated with the lagoons seen on dermoscopy, thus strongly supporting the final diagnosis of THs in both cases.

Aortic body chemodectoma in a cow: clinical, morphopathological, and immunohistochemical study

A 3-year-old Holstein cow with a history of severe weakness, dyspnea, pale mucous membranes, increased respiratory rate associated with marked abdominal respiration, severe arrhythmia, and tachycardia was referred to a slaughterhouse by the referring veterinarian due to poor prognosis. After slaughter, a large, firm, white, multilobulated mass about 5 cm in diameter was located at the base of the heart that extended to the right atrium and obliterated partially the right atrial lumen. Microscopically, tumor cells were aligned along and around the capillaries and were discrete, cuboidal to polyhedral cells with little cytoplasm arranged in distinct packets surrounded by thin fibrous septa. The nuclei were round to oval and were placed centrally in the cells. Immunoreactivity for S100 protein was positive multifocally, mostly in the peripherally located sustentacular cells, but NSE and CrA were negative. On the basis of the clinicopathological and immunohistochemical findings, the tumor was diagnosed as aortic body chemodectoma.

Focal Nodular Hyperplasia in the Livers of Cynomolgus Macaques (Macaca Fascicularis)

Two cases of spontaneous focal hepatic hyperplasia were observed in young female cynomolgus macaques (Macaca fascicularis). Grossly, a single raised nodule was observed in the left hepatic lobe. Histopathologically, the nodule compressed surrounding normal tissue; however, the hepatic cords within the nodule continued to those in the nor mal area except in part. Extensive fibrosis and absence of a normal hepatic triad were observed in the nodule. Thin fibrous septa radiating from the dense central stellate scarring and distended vessels were apparent in one animal. Hepatocytes in the nodule lacked cellular atypia, showed frequent PAS-positive eosinophilic inclusions in the cytoplasm and showed higher positive ratios for PCNA. The present cases resembled focal nodular hyperplasia reported in humans and a chimpanzee.

Fibrinogen Storage Disease Caused by Aguadilla Mutation Presenting With Hypobeta‐lipoproteinemia and Considerable Liver Disease

Fibrinogen Storage Disease Caused by Aguadilla Mutation Presenting With Hypobeta‐lipoproteinemia and Considerable Liver Disease

Cutaneous Clear Cell Adnexal Carcinoma in a Dog: Special Reference to Cytokeratin Expression

A 5-year-old, male Bichon-Frise dog presented with a cutaneous mass in the basal region of the auricle. Histologically, the cutaneous neoplasm was comprised of lobules with solid cellular proliferation separated by thin fibrous septa. Neoplastic cells varied in size, with moderate to abundant amounts of PAS-positive cytoplasm, large nuclei and prominent nucleoli. Immunohistochemical examinations showed that tumor cells were positive for pan-cytokeratin (CK) (AE1/AE3 and CAM5.2), CK8 and CK18, but negative for pan-CK (KL1), CK7, CK14, CK16 and CK20. Double-labeled immunofluorescence testing indicated that neoplastic cells frequently co-expressed CK and vimentin, suggesting divergent differentiation of tumor cells. Based on these findings, the tumor was diagnosed as canine clear cell adnexal carcinoma.

Electronic Clinical Challenges and Images in GI

Electronic Clinical Challenges and Images in GI

Do diabetes and obesity promote hepatic fibrosis in familial heterozygous hypobetalipoproteinemia?

The course of NAFLD secondary to familial heterozygous hypobetalipoproteinemia (FHBL), a definite etiology of secondary nonalcoholic fatty liver disease (NAFLD) [1–3] featuring low density lipoprotein cholesterol (LDL-C) and apolipoprotein B (ApoB) plasma levels less than fifth percentile [4], is unknown. We report on a case with FHBL due to compound heterozygosity and apoB non-detectable in serum in which a long-term follow-up and paired liver biopsies were available. A 58 year-old obese woman with FHBL was observed in June 2007 for abdominal pain and poorly controlled type 2 diabetes (T2D). The T2D began at the age of 40. It was complicated by peripheral neuropathy of the legs, and a chronic vascular encephalopathy that was documented by computed tomography. The patient was initially treated with a combination therapy (i.e., metformin plus glibenclamide plus insulin). Additional medications used were gabapentin for the peripheral neuropathy, thiamazole for multinodular hyperthyroidism, and escitalopram for mild psychodepressive disorder. The patient’s alcohol consumption was nil. Laparoscopic cholecystectomy had been performed in 1998 for acute biliary pancreatitis. At that time, intraoperative wedge liver biopsy disclosed NAFLD type 1–2 according to Matteoni et al. with thin fibrous septa [5] (Fig. 1). BMI was 30 Kg/m. An abdominal ultrasound imaging (US scan) suggested steatosis. Plasma lipid values compatible with FHBL had been noted since 1998 (total Cholesterol 61 mg/dl, LDL-C 21 mg/dl, HDL-C 28 mg/ dl, Triglycerides 50 mg/dl, ApoA1 83 mg/dl, ApoB \ 40 mg/dl). The apoB gene molecular analysis confirmed a severe form of FHBL in 2005. The patient is a double heterozygote for two mutations both with pathologic effect. The first one is a non-sense mutation (G?A), in hexon 19, resulting in a truncated apoB (apoB-20.6), not secreted in plasma. The second one is a nucleotidic substitution (T?A) in intron 14 (IVS 14 -4T/A) whose translation product would be a small-size truncated apoB, and so not secreted. In June 2007, the patient’s BMI was 41 Kg/m. Glycemic control was poor (fasting glucose 464 mg/dl at admission, hemoglobin A1c 11%). The liver chemistry tests were substantially normal (AST 28 U/l, ALT 25 U/l, GGT 32 U/l, ALP 53 U/l, bilirubin 0.6 mg/dl, albumin 3.2 g/dl, INR 0.83). Thyroid function tests were normal too (TSH 0.36 lIU/ml, FT4 9.9 pg/ml, FT3 2.3 pg/ml). A repeat liver biopsy showed advanced fibrosing-NASH in the pre-cirrhotic stage with marked steatosis (Fig. 2). The antinuclear antibody test, extractable nuclear antigens, antimitochondrial antibodies, anti-HCV antibodies, and HbsAg and Lupus Anticoagulant studies were all negative. The HBsAb ([22 mIU/ml) and anti-smooth muscle antibody (1:80) were positive. The US scan confirmed hepatomegaly, with hyperechoic structure and mild hypertrophy of the spleen. S. Ballestri A. Lonardo E. Pellegrini M. Bertolotti P. Loria (&) Department of Internal Medicine, Endocrinology, Metabolism and Geriatrics, University of Modena and Reggio Emilia, Nuovo Ospedale Civile Sant’Agostino Estense di Baggiovara, Via Giardini 1355, 41100 Modena, Italy e-mail: loria.paola@unimore.it

Unusual Benign Myxoid Nerve Sheath Lesion: Myxoid Palisaded Encapsulated Neuroma (PEN) or Nerve Sheath Myxoma With PEN/PEN-like Features?

A 38-year-old woman had a polypoid nodule on her scalp. The lesion histopathologically demonstrated an extensive myxoid lobular lesion associated with a nonmyxoid and cellular area in the peripheral area of the lesion. The features of the peripheral cellular area resembled those of palisaded encapsulated neuroma (PEN). Most of the lesion was myxoid, with a large lobule in which several thin fibrous septa were present, dividing it into smaller lobules. The myxomatous area was composed of spindle cells or stellate cells with elongated cytoplasmic processes. There was a loose cellular network with a reticular and netlike network pattern or a lamellar pattern. From the immunohistochemical findings, as well as the histopathologic features, the whole lesion was thus considered to be a PEN, whereas the main, myxoid, lobular lesion was thought to have been caused by myxoid changes within a PEN, namely, myxoid PEN. It cannot be completely ruled out, however, that this case could be that of a nerve sheath myxoma with a PEN/PEN-like lesion. Thus, the present case may suggest that PEN can show extensive myxoid change or may demonstrate a relationship between PEN and nerve sheath myxoma.

Colonic Lipoma With Intussusception

A 51-year-old woman was admitted to the hospital with a 20-day history of intermittent abdominal cramping. Her stools had decreased in volume and had become watery. Physical examination revealed no fever or palpable mass. Computed tomography in the axial plane showed an intussusception of the transverse colon due to a primary mass with dominant fatty density. The relationship of the intussusception to the mass was well delineated on oblique multiplanar reformation, and a diagnosis of colonic lipoma was considered. The patient's obstructive symptoms resolved spontaneously, and she was hesitant about undergoing surgery. However, recurrence of her symptoms a few days later prompted exploratory laparotomy, which revealed a long-stalked mass approximately 7 × 6 × 5 cm at the transverse colon near the hepatic flexure. Resection of the tumor revealed multiple yellowish lobules. Pathologic examination disclosed a lipoma with no evidence of malignancy. Colonic lipomas are relatively rare and frequently asymptomatic. Most gastrointestinal lipomas arise in the submucosa. The colon is commonly affected, followed by the small intestine and then the stomach. Large lipomas may be associated with complications such as intussusception or intestinal bleeding.1Kabaalioglu A Gelen T Aktan S Kesici A Bircan O Luleci E Acute colonic obstruction caused by intussusception and extrusion of a sigmoid lipoma through the anus after barium enema.Abdom Imaging. 1997; 22: 389-391Crossref PubMed Scopus (12) Google Scholar Colonoscopic biopsy is usually performed to confirm the nature of the tumor. However, inadequate tissue samples often indicate nonspecific colitis because of adjacent mucosal inflammation produced by the lipoma.2Zhang H Cong JC Chen CS Qiao L Liu EQ Submucous colon lipoma: a case report and review of the literature.World J Gastroenterol. 2005; 11: 3167-3169Crossref PubMed Scopus (52) Google Scholar Computed tomography clearly reveals the characteristic fatty densitometric features of lipomas.3Liessi G Pavanello M Cesari S Dell'Antonio C Avventi P Large lipomas of the colon: CT and MR findings in three symptomatic cases.Abdom Imaging. 1996; 21: 150-152Crossref PubMed Scopus (41) Google Scholar Most lipomas demonstrate homogeneous fatty density with a thin fibrous septa, depending on the tumor size. If prominent fibrous septa and nodularity are evident, the most imperative differential diagnosis is a well-differentiated liposarcoma, despite the few reports of gastrointestinal liposarcomas in the literature.4Pereira JM Sirlin CB Pinto PS Casola G CT and MR imaging of extrahepatic fatty masses of the abdomen and pelvis: techniques, diagnosis, differential diagnosis, and pitfalls.Radiographics. 2005; 25: 69-85Crossref PubMed Scopus (137) Google Scholar

Colonic Lipoma With Intussusception

A 51-year-old woman was admitted to the hospital with a 20-day history of intermittent abdominal cramping. Her stools had decreased in volume and had become watery. Physical examination revealed no fever or palpable mass. Computed tomography in the axial plane showed an intussusception of the transverse colon due to a primary mass with dominant fatty density. The relationship of the intussusception to the mass was well delineated on oblique multiplanar reformation, and a diagnosis of colonic lipoma was considered. The patient's obstructive symptoms resolved spontaneously, and she was hesitant about undergoing surgery. However, recurrence of her symptoms a few days later prompted exploratory laparotomy, which revealed a long-stalked mass approximately 7 × 6 × 5 cm at the transverse colon near the hepatic flexure. Resection of the tumor revealed multiple yellowish lobules. Pathologic examination disclosed a lipoma with no evidence of malignancy. Colonic lipomas are relatively rare and frequently asymptomatic. Most gastrointestinal lipomas arise in the submucosa. The colon is commonly affected, followed by the small intestine and then the stomach. Large lipomas may be associated with complications such as intussusception or intestinal bleeding.1Kabaalioglu A Gelen T Aktan S Kesici A Bircan O Luleci E Acute colonic obstruction caused by intussusception and extrusion of a sigmoid lipoma through the anus after barium enema.Abdom Imaging. 1997; 22: 389-391Crossref PubMed Scopus (12) Google Scholar Colonoscopic biopsy is usually performed to confirm the nature of the tumor. However, inadequate tissue samples often indicate nonspecific colitis because of adjacent mucosal inflammation produced by the lipoma.2Zhang H Cong JC Chen CS Qiao L Liu EQ Submucous colon lipoma: a case report and review of the literature.World J Gastroenterol. 2005; 11: 3167-3169Crossref PubMed Scopus (52) Google Scholar Computed tomography clearly reveals the characteristic fatty densitometric features of lipomas.3Liessi G Pavanello M Cesari S Dell'Antonio C Avventi P Large lipomas of the colon: CT and MR findings in three symptomatic cases.Abdom Imaging. 1996; 21: 150-152Crossref PubMed Scopus (41) Google Scholar Most lipomas demonstrate homogeneous fatty density with a thin fibrous septa, depending on the tumor size. If prominent fibrous septa and nodularity are evident, the most imperative differential diagnosis is a well-differentiated liposarcoma, despite the few reports of gastrointestinal liposarcomas in the literature.4Pereira JM Sirlin CB Pinto PS Casola G CT and MR imaging of extrahepatic fatty masses of the abdomen and pelvis: techniques, diagnosis, differential diagnosis, and pitfalls.Radiographics. 2005; 25: 69-85Crossref PubMed Scopus (137) Google Scholar

Gastrointestinal: Gastrointestinal lipomas

Lipomas are benign tumors composed of multiple discrete masses of fat separated by thin fibrous septa. In the gastrointestinal tract, at least 70% of lipomas are located in the large bowel but other sites include the small bowel (25%) and stomach (5%). In the large bowel, the majority of lipomas are located in the cecum and ascending colon. However, true lipomas close to the ileocecal valve need to be distinguished from fatty infiltration of the valve, a common disorder which is sometimes called lipohyperplasia. Lipomas are usually solitary but vary widely in size, shape and consistency. Some are sessile nodules that project into the bowel lumen while others are polypoid tumors that are largely intraluminal. A characteristic feature is a shiny, yellowish lesion covered by normal mucosa. In relation to consistency, some are firm, others are spongy with a ‘pillow cushion sign’ and a minority are soft and flaccid, particularly those in the stomach. Most lipomas are asymptomatic. However, larger lesions can ulcerate and bleed and there are case reports of partial or complete bowel obstruction, sometimes with intussusception. The patient whose images are shown in Figure 1 was a 40-year-old woman who had a colonoscopy because of episodes of lower abdominal pain. A large polyp, approximately 4 cm in diameter, with surface ulceration was identified in the region of the hepatic flexure. As biopsies were inconclusive, a right hemicolectomy was performed that revealed an elongated tumor, 5.5 cm × 3 cm in size, with apical ulceration. Histological evaluation revealed typical features of a lipoma. The image in Fig. 2 was a polypoid lesion in the transverse colon. The lesion was identified as a probable lipoma because of the smooth, shiny surface with yellowish coloration. The polyp was resected by loop diathermy and had typical histological features of a lipoma. Care should be taken with the endoscopic resection of sessile lipomas as there appear to be significant risks for colonic perforation and bleeding.

Immunohistochemical Characterization of the Leucocytic Infiltrate Associated with Canine Seminomas

Both canine and human seminomas are typically associated with leucocytic infiltration, the role of which remains poorly understood. In this study, leucocytes infiltrating 10 canine seminomas were characterized. Monoclonal antibodies directed against CD18, CD11a, CD11b, CD11c, CD21, CD3, CD4, CD8 and Major Histocompatibility Complex class I and II (MHC I and MHC II) were also employed. Infiltrating leucocytes were located around vessels, adjacent to the thin fibrous septa between neoplastic lobules, and were also scattered singly amongst neoplastic cells. The more profuse infiltrates often had the appearance of follicular aggregates. Immunohistochemically, all the samples showed generally similar results. Most of the infiltrating cells were positive for CD18 and CD11a. Infiltrating cells were mainly T lymphocytes (CD3 +), particularly of the CD8 + subset. B lymphocytes (CD21 +) were detectable in almost all infiltrates; in the follicular aggregates they were centrally located, whereas T lymphocytes (CD3 +) lined the periphery. CD11c + cells were always more numerous than CD11b + cells, demonstrating that if macrophages and antigen-presenting cells (APCs) were well represented, monocytes and granulocytes were practically absent. Almost all of the infiltrating cells were positive for both MHC I and MHC II antigens and, in nine samples, a large number of neoplastic cells expressing MHC I were detected. A few neoplastic cells expressing MHC II were observed in seven cases. The presence of CD8 + lymphocytes, together with the large number of both infiltrating and neoplastic cells expressing MHC I, suggests that the lymphocytes mediate a cytotoxic reaction against the neoplastic cells. This hypothesis may underlie the favourable prognosis frequently associated with canine seminomas.

First histologically confirmed case of a classic chordoma arising in a precursor benign notochordal lesion: differential diagnosis of benign and malignant notochordal lesions

The first histologically confirmed case of a classic chordoma arising in a precursor benign notochordal lesion is presented and the differential diagnosis between benign and malignant notochordal lesions is discussed. A 57-year-old man presented with a classic chordoma in the coccyx. The resected specimen demonstrated a small intraosseous benign notochordal lesion in the coccyx, which was adjacent to the classic chordoma. Also seen were two separate, similar benign lesions in the sacrum. The classic chordoma consisted of multiple lobules that were separated by thin fibrous septa and that showed cords or strands of atypical physaliphorous cells set within an abundant myxoid matrix. In contrast, the benign lesions consisted of intraosseous sheets of bland physaliphorous cells without any extracellular matrix. The affected bone trabeculae showed sclerotic reactions. It was concluded that benign and malignant notochordal lesions can be distinguished microscopically.

Pathology and pathogenesis of idiopathic portal hypertension with an emphasis on the liver.

Idiopathic portal hypertension (IPH) is characterized by a long-standing presinusoidal portal hypertension of unknown etiology in adults. Some unidentified agent(s) affect(s) the intrahepatic small portal veins or portal tracts. Immunological disturbance, thromboembolism, infectious etiology and/or increased fibrogenesis in portal tracts are suspected as being candidates for the primary agent(s). During the long clinical course of IPH, several pathological changes may occur, including subcapsular parenchymal atrophy, atrophy of the liver, portal and parenchymal fibrosis, and portal venous phlebosclerosis and thrombosis. The last-named of these lesions is mostly found in patients with a history of splenectomy. Subcapsular parenchymal and hepatic atrophy may result from a hepatocellular dropout via apoptosis or necrosis because of intrahepatic hemodynamic disturbances, particularly chronic portal venous blood insufficiency. Pericellular fibrosis and thin fibrous septa are also frequently found and associated with activated perisinusoidal cells positive for smooth muscle actin. At the same time, vague nodular hyperplasia of hepatocytes not surrounded by fibrous septa is not infrequently seen. It may resemble nodular regenerative hyperplasia, partial nodular transformation, or focal nodular hyperplasia. However, liver cirrhosis does not occur even at the terminal stage. Taking these findings into consideration, a new staging of IPH with a combination of hepatic parenchymal atrophy and portal venous thrombosis was proposed: non-atrophic liver without subcapsular parenchymal atrophy (stage I), non-atrophic liver with subcapsular parenchymal atrophy (stage II), atrophic liver with subcapsular parenchymal atrophy (stage III), and portal venous occlusive thrombosis (stage IV). IPH livers are likely to progress from stage I to stage III. Stage IV, which occurs relatively late, has a poor prognosis. This staging is applicable to clinical and autopsy cases without any histological data.

Intratumoral genomic heterogeneity in human hepatocellular carcinoma detected by restriction landmark genomic scanning

Background/Aims: One of the unique features of advanced hepatocellular carcinoma (HCC) is the morphological heterogeneity in a single tumor nodule. In order to investigate the intratumoral genomic heterogeneity of HCC, we performed Restriction Landmark Genomic Scanning (RLGS), which allows genomic DNAs to be surveyed at approximately 2000 landmark sites in a single 2-dimensional gel electrophoresis. Methods: RLGS profiles of two regions from a single HCC nodule in six patients were compared with nontumorous liver tissue. Four HCCs consisting of moderately-differentiated cells were separated into several small parts by thin fibrous septa, but not encapsulated. DNA samples were obtained from both parts of these so-called “nodule-in-nodule” HCC. Two HCCs consisting of well-differentiated cells which did not have a definite partition appeared pathologically homogeneous, and two independent regions of the HCC were used for the analysis. Results: All six HCCs demonstrated different RLGS profiles (in total about 160 different spots) from the corresponding non-tumorous liver, and the number of different spots was greater in the 4 moderately-differentiated nodule-in-nodule HCCs (39–68 spots) than in the 2 well-differentiated homogeneous HCCs (6 and 3 spots). RLGS profiles of the two parts were different to each other in all 4 nodule-in-nodule HCCs. On the other hand, two other homogeneous HCCs showed the same RLGS profiles in the two regions. Conclusion: Thus, intratumoral genomic heterogeneity was demonstrated in the advanced HCC samples, and the genomic alterations may relate to the progression of HCC.

Biochemical and histological features of hepatitis G virus infection.

To assess the biochemical and histological characteristics of hepatitis G virus (HGV) infection, we examined four patients who were infected with HGV only (HGV group), and compared them with 16 patients infected with both HGV and hepatitis C virus (HCV; HGV + HCV group) and 18 patients infected with HCV only (HCV group). Biochemical examination showed a significantly low level of serum alanine aminotransferase (ALT) in the HGV group, and that the gamma-glutamyl transpeptidase (gamma-GTP)/ALT ratio in the same group was significantly higher than in the other two groups. Although all three patient groups had a similar degree of liver fibrosis, both the degree of periportal inflammation and total histological activity index were significantly lower in the HGV group than in the other two groups. Fibrous enlargement of the portal tract without lymphoid infiltration and thin fibrous septa was characteristically observed in the HGV group. No significant difference was found between the HGV + HCV group and HCV group. Our results suggest that biochemical and histological changes in HGV infection are very mild and quite different from those of HCV infection.

Avascular Tympanojugular Paraganglioma

The avascular paraganglioma described in this article appears to be the second such tumor reported in the international literature and the first to be reported in the tympanojugular region. Despite a highly suggestive history and clinical appearance, the tumor showed no signs of vascularization on radiologic studies. The pathologic postoperative study confirmed the diagnosis of paraganglioma with extensive stromal fibrosclerosis and without the typical well-vascularized thin fibrous septa. In the authors' opinion, this observation is notable because of the difficulties encountered in the correct diagnostic interpretation of an avascular mass in the tympanojugular region. In such cases, the possibility of a paraganglioma should always be considered.

Apocrine nevus: light microscopic, immunohistochemical and ultrastructural studies of a case

The apocrine nevus (AN) is a rare tumor occurring in the upper chest and the axilla. We report a case of a AN in a 33-year-old female occurring unilaterally. The presenting complaint related to tenderness and swelling in the right axilla. The initial impression was hidradenitis suppurativa. The gross specimen revealed the presence of irregular thickening just beneath the dermal subcutaneous interface. Microscopically the lesion was composed of mature apocrine glands with apical snouts. The glands were arranged in lobules divided by thin fibrous septa. Immunohistochemical studies revealed the following profile in the glandular epithelium: positive low molecular weight cytokeratin, epithelial membrane antigen, and gross cystic disease fluid protein reactivity and negative high molecular cytokeratin and S-100 protein reactivity. Carcinoembryonic antigen reactivity was found in the duct epithelium. Ultrastructural studies revealed cells lining the lumen of the glands with a concentration of granules in the apical region and light and dark granules. These findings support the previously described light microscopic observations and provide unreported ultrastructural studies in this rare tumor.