Microcystic Structures Research Articles

Tubulocystic Carcinoma of Bile Ducts: A Distinct Type of Cholangiocarcinoma Associated With Adenofibroma-type Lesions.

A type of cholangiocarcinoma (CCA) characterized by peculiar histologic patterns and underlying adenofibromatous lesions has been reported in the literature mostly as individual case reports. This study aims to further clarify the defining characteristics of this spectrum of lesions. Clinicopathologic analysis of 8 biliary tumors with tubulocystic architecture arising in the background of adenofibroma-type lesions was performed. Three of these were also investigated with next-generation sequencing with a 174 genes panel. The patients were 5 males and 3 females, with a mean age of 64.6. All tumors were intrahepatic except for one perihilar that protruded into soft tissues. The mean size was 4.4 cm. At histology, all cases showed a peculiar and cytologically bland tubulocystic pattern that closely resembled tubulocystic-type kidney cancers, including back-to-back microcystic units that formed relatively demarcated nodules, and occurring in the background of adenofibromatous lesions. One case showed perineural invasion by otherwise deceptively benign-appearing microcystic structures, one had areas transitioning to intraductal tubulopapillary neoplasm, and 3 cases harbored more conventional small-duct CCA foci. In those 3 cases, both the tubulocystic and conventional CCA components were investigated by next-generation sequencing separately, and they shared the molecular alterations, including recurrent mutations in chromatin remodeling genes, such as ARID1A , BAP1 , and PBRM1 , and the actionable FGFR2-MCU fusion gene. In the limited follow-up, all but one were alive and free of disease after surgical resection. In conclusion, we described a distinct entity of CCA with specific histo-molecular features, for which we propose the designation of tubulocystic carcinoma of bile ducts.

A Parotid Gland Mammary Analogue Secretory Carcinoma in a 4-Year-Old Boy: Case Report and Literature Review

Background: Mammary analogue secretory carcinoma (MASC) is characterized by similar histologic, immunohistochemical, and molecular features with breast secretory carcinoma. MASC usually occurs in adults. Case report: A 4-year-old boy presented with a right infra-auricular mass. Features of the tumor include solid, tubular, and papillary growth patterns, with homogenous eosinophilic secretions inside microcystic structures. Immunohistochemical stains showed strong, diffuse staining for CK7, S100, pan-TRK protein. P63 was positive in a peripheral pattern. Fluorescence in situ hybridization (FISH) analysis showed the characteristic ETV6-NTRK3 gene fusion. Conclusion: Typical histological, immunohistochemical, and molecular features are present in MASC occurring early in childhood.

GLANDULAR ODONTOGENIC CYST IN ANTERIOR MANDIBLE: A CASE REPORT

A 35-year-old male patient was referred to the oral clinic complaining of a sensitivity in the right lower canine, without gingival edema or any other sign. On radiographic examination, a well-defined multilocular, radiolucent lesion associated with the roots of the lower incisor and canine was noted. The initial clinical diagnostic hypotheses were ameloblastoma or keratocyst. After complete removal of the lesion by curettage, microscopic examination revealed a thin and friable cystic capsule and lining composed of nonkeratinized stratified squamous epithelium as well as superficial cuboidal eosinophilic cells and intra-epithelial microcystic structures. The final diagnosis of glandular odontogenic cyst was made. Surgical treatment of the lesion was successful and the patient is being followed up. Since surgical treatment, the patient has been followed up with no evidence of recurrence.

Secretory Carcinoma of the Breast in a 24-Year-Old Woman: A Case Report

Secretory carcinoma of the breast is a rare invasive carcinoma. This carcinoma shows more aggressive symptoms in older patients. In a reported case of a 24-year-old woman with a mass in her right breast, the histopathologic features consisted of tumor cell proliferation and most of it came in tubular and microcystic structures. The cell nuclei enlarged into a round and oval shape. The chromatin was coarse and came with some protuberant nucleus, foamy, and slightly granular eosinophilic cytoplasm.

A case of mammary analogue secretory carcinoma of the parotid gland

Rationale:Mammary analogue secretory carcinoma is a low grade salivary gland malignancy, first described by Skalova et al in 2010. The histological, immunohistochemical, and molecular characteristics of this tumor resemble those of secretory carcinoma of the breast.Patient concerns:A 40-year-old male patient without any specific past history came with complaints of 4 cm-sized hard, fixed, right infra-auricular mass without tenderness. There was no enlarged or enhancing lymph node in both neck.Diagnoses:Fine needle aspiration biopsy was done for right parotid mass and pathologic report was ”lymphocytes only” that suggested benign or low-grade malignant parotid tumor.Interventions:Partial parotidectomy including mass excision was performed. Operative finding showed hard bluish mass located in deep lobe of right parotid gland.Outcomes:Final pathologic report revealed secretory carcinoma of parotid gland. Homogenous eosinophilic secretions were identified inside microcystic structure. The immunophenotype was positive for epithelial membrane antigen, vimentin, S-100 protein. After 15 months of the surgery, the patient showed negative evidence of disease state.Lessons:We present here a case of mammary analogue secretory carcinoma of the parotid gland to help further characterize this rare tumor.

Genotype correlates with clinical severity in PIK3CA-associated lymphatic malformations.

Lymphatic malformations (LMs) are congenital, nonneoplastic vascular malformations associated with postzygotic activating PIK3CA mutations. The mutation spectrum within LMs is narrow, with the majority having 1 of 3 hotspot mutations. Despite this relative genetic homogeneity, clinical presentations differ dramatically. We used molecular inversion probes and droplet digital polymerase chain reaction to perform deep, targeted sequencing of PIK3CA in 271 affected and unaffected tissue samples from 81 individuals with isolated LMs and retrospectively collected clinical data. Pathogenic PIK3CA mutations were identified in affected LM tissue in 64 individuals (79%) with isolated LMs, with variant allele fractions (VAFs) ranging from 0.1% to 13%. Initial analyses revealed no correlation between VAF and phenotype variables. Recognizing that different mutations activate PI3K to varying degrees, we developed a metric, the genotype-adjusted VAF (GVAF), to account for differences in mutation strength, and found significantly higher GVAFs in LMs with more severe clinical characteristics including orofacial location or microcystic structure. In addition to providing insight into LM pathogenesis, we believe GVAF may have broad applicability for genotype-phenotype analyses in mosaic disorders.

MAMMARY ANALOG SECRETORY CARCINOMA OF SALIVARY GLANDS:A CASE REPORT.

Objective Mammary analog secretory carcinoma(MASC), is a distinctive low-grade malignant salivary cancer. Microscopically, most cases of MASC consist of a circumscribed mass divided by thin fibrous septa into lobules composed of microcystic, tubular, and solid structures. Due to the scarcity of reported cases, however, little information exists regarding this lesion in the salivary gland. Here, we report a case of MASC occurring in the parotid gland. Clinical Presentation Our patient is a 28-yer-old male who presented with a 3.0 × 2.5 × 2.0cm in the right parotid gland, referred slowly growing, painless approximately one year duration. The tumor is rubbery, with a white-tan to gray cut surface. On the cut surface of the mass, many small cystic spaces may be seen, containing yellow to whitish fluid. The borders of the tumor is circumscribed but not encapsulated. Conclusion Most cases of MASCs were diagnosed as AciCC or adenocarcinoma not otherwise specified. Many MASC were found to harbor an ETV6-NTRK3 fusion gene because of a t(12;15) (p13,q25) translocation, a finding identical to secretory carcinoma of the breast. The most recent version of the World Health Organization (WHO) Classification of Head and Neck Tumours utilizes the terminology of “secretory carcinoma” for consistency. In addition to the case report, we review the past and current cases enrolled of MASC. Awareness of such a clinical presentation is important for the clinician.

Cystadenocarcinoma: Report of a Rare Case in Oral Cavity

Cystadenocarcinoma is a rare tumor of the oral cavity, recently reclassified by the World Health Organization as synonymous with adenocarcinoma, not otherwise specified. This report describes a case of cystadenocarcinoma in the buccal mucosa. A 72-year-old woman was referred for diagnosis of a lesion, of unknown duration, located in the right buccal mucosa. Intraorally, the lesion appeared as a well-delimited, mobile, and submucosal nodule. A benign mesenchymal neoplasm was the main hypothesis of diagnosis. Microscopic analysis revealed a salivary gland neoplasm formed by atypical cells arranged in microcystic structures, with frequent intraluminal papillary projections. The tumor cells exhibited positivity for CK7 and negativity for CK20. Based on these features, a diagnosis of cystadenocarcinoma was established. The patient was submitted to wide surgical resection. No recurrence was observed after 12 months. Although rare, cystadenocarcinoma should be considered in the differential diagnosis of oral submucosal nodules.

Secretory Carcinoma in the Buccal Mucosa

Secretory carcinoma (SC) is a malignancy of the salivary glands, described by Skálová et al in 2010 as mammary analogue secretory carcinoma (MASC). Previously, the lesion was diagnosed as an unusual variant of acinic cell carcinoma (AciCC). The World Health Organization Classification of Head and Neck Tumors in 2017 simplified the name from MASC to SC. We described the case of a 27-year-old woman showing a round, circumscribed lesion in the buccal mucosa, resembling a mucocele. After an incisional biopsy, the microscopic analysis exhibited circumscribed lobulated masses under the epithelium, composed of microcystic structures. The cells presented a pale eosinophilic cytoplasm and vesicular nuclei with distinctive centrally located nucleoli. Immunohistochemistry analysis showed positivity for S-100 and mammaglobin. Fluorescence in situ hybridization detected the ETV6 gene rearrangement, confirming the diagnosis of secretory carcinoma. The patient underwent non-radical surgical excision, is under a follow-up for 10 months, and shows no local recurrences.

MEDIASTINAL YOLK SAC TUMOR INFILTRATING THE HEART

As a rare tumor, yolk sac tumor is a type of neoplasm that appears like the yolk sac, extraembryonic mesenchyme, and allantois. The mediastinum is the second most frequent area after the gonadal area. We present an extremely rare case of 15years old boy with mediastinal yolk sac tumor. The boy came with the chief complaint of swelling of the neck and face. Computed tomography scan of the chest revealed bulky mass with a cystic component that infiltrated the heart. The diagnosis of mediastinal yolk sac tumor was made after core needle biopsy. Histopathologic analysis revealed tumor mass with solid and microcystic structure and pleomorphic nucleus within the tumor cells. Laboratory finding showed elevated serum alpha-fetoprotein level reaching more than 8000ng/ml. Echocardiography revealed a mass in the right atrium. The patient condition was rapidly deteriorated due to his vena cava superior syndrome. Unfortunately, the patient died two days after diagnosis and we did not have the chance to do the therapy. Mediastinal yolk sac tumor is a rare malignancy that requires comprehensive management. The diagnosis should be made based on histopathological findings with the addition of thoracic computer tomography scan to assess the degree of infiltration to surrounding organ. A life-threatening condition such as vena cava superior syndrome should be assessed promptly to allow for immediate treatment.

A Case of Acinic Cell Carcinoma Involving Skin.

Dear Editor: A 62-year-old man presented with a 5-month history of solitary subcutaneous nodule on the right cheek that. On physical examination, there was a 2-cm flesh-toned subcutaneous round nodule on the right cheek (Fig. 1). The mass was soft and somewhat fluctuant on palpation without tenderness. Histopathologic examination revealed multiple well-circumscribed tumor nests with solid, lobular, and microcystic structures (Fig. 2A). A large portion of tumor cells displayed serous acinar differentiation with cytoplasmic granules, termed cytoplasmic zymogen-like granules (Fig. 2B). The cytoplasmic granules were periodic acid-Schiff (PAS)-positive and diastase-resistant (Fig. 2C). Moderate nuclear pleomorphism and hyperchromasia were present. Immunohistochemical staining revealed that the tumor cells were immunopositive for cytokeratin, α-1 antitrypsin, and α-1 antichymotrypsin (Fig. 2D~F), while they were immunonegative for S100 protein. We diagnosed the patient with secondary cutaneous acinic cell carcinoma (ACC) that had locally advanced from the right parotid gland. Fig. 1 A single 2-cm sized flesh-toned subcutaneous round nodule on the right cheek. Fig. 2 (A) Tumor nests with variable growth patterns, including solid, lobular, and microcystic patterns (H&E, ×15). (B) Tumor cells with serous acinar differentiation and cytoplasmic granules, termed cytoplasmic zymogen-like granules (H&E, ... ACC is a malignant salivary gland neoplasm that accounts for 20% of all salivary gland malignancies, and 90% of cases arise in the parotid gland. The onset incidence peaks in the fifth and sixth decades although age at onset varies from 5 years to over 80 years of age1. ACC presents as a painless subcutaneous nodule. In rare cases, pain and tenderness can occur intermittently. Facial paralysis, which occurs in 11% of cases, is usually a serious prognostic sign2. Cutaneous ACC metastasis is rare, with only a few reported cases3. Microscopically, primary tumors can present with four characteristic growth patterns: solid/lobular, microcystic, papillary cystic, and follicular, with several patterns often seen in the same tumor. The diagnostic feature of ACC is the presence of at least some neoplastic cells demonstrating serous acinar differentiation, which is characterized by cytoplasmic zymogen secretory granules4. These tumor cells are polygonal with lightly basophilic to amphophilic fine granules in the cytoplasm. The granules are characteristically PAS-positive and diastase-resistant. In addition to serous cells, there may also be clear cells, intercalated duct cells, vacuolated cells, and non-specific glandular cells4. Tumor size, degree of differentiation, and infiltrative growth patterns are useful in predicting clinical courses5. Immunohistochemistry showed that tumor cells can be positive for cytokeratin, α-1 antichymotrypsin, α1-antitrypsin, and lysozyme, with approximately 10% of cells positive for S100 protein. However, there is no specific immunoprofile, and immunohistochemistry has little impact on diagnosis4. ACC diagnosis is usually confirmed with fine-needle aspiration biopsy, and surgical excision is the treatment of choice. Radiation therapy is generally reserved for more aggressive or recurrent tumors, while neck dissection is performed in patients with clinically positive nodes. In one study, the 5-year survival rates were 83.3% (observed) and 91.4% (disease-specific), and poor survival was associated with high grade, patient age >30 years, and metastatic disease1. We have here reported a rare case of secondary cutaneous ACC presenting as solitary subcutaneous nodule on the right cheek in a 62-year-old man. When examining dermal or subcutaneous tumors of the face, tumors originating from the salivary gland should be considered.

Distinctive immunostaining of claudin-4 in spiradenomas.

The intercellular bridges are essential structures in maintaining the histologic organization of the epithelium, while providing a very efficient way to exchange molecules between cells and transduction of the cell-to-cell and matrix-to-cell signals. Derangement in those important structures' physical integrity and/or function, which can be assessed by the presence or absence of several intercellular bridge proteins including claudin-4, E-cadherin, and β-catenin, was found to be related to several phenomena in the path to the neoplastic transformation. However, these proteins have not been studied in the wide variety of the skin neoplasms, in detail. Herein, we immunohistochemically assessed the expression patterns of these 3 intercellular bridge proteins on a total of 86 epidermal and eccrine adnexal tumors including basal cell carcinoma, squamous cell carcinoma, poroma, spiradenoma, syringoma, and hidradenoma. We observed a selective and distinct claudin-4 expression in the ductal-type cells of all cases of spiradenomas. Similarly, in the poromas, syringomas, and hidradenomas, claudin-4 was only positive in the luminal cells of microcystic structures, although not as conspicuous as in the spiradenomas. On the other hand, E-cadherin and β-catenin were positive in almost all types of the tumors, in a way which was not contributory to differentiate from each other. In conclusion, we think that claudin-4 can be helpful at least in making a reliable differential diagnosis of spiradenoma when overlapping morphologic features do not allow to further subclassification in the overwhelming variety of the adnexal tumors.

Nephrogenic Adenoma of the Urinary Tract

Nephrogenic adenoma (NA) is an uncommon and intriguing lesion in the urinary tract. The pathogenesis of NA is not entirely clear. NA was considered to be a metaplastic process of the urothelium in response to chronic irritation of the urinary tract. However, recent evidence has shown that NA is not a metaplastic lesion but rather a proliferation of exfoliated and implanted renal epithelial cells in the urinary tract. Histologically, NAs exhibit, singly or in combination, tubules, small papillae, and microcystic structures lined by cells with little cytological atypia and focal hobnail changes. Solid formations and compressed spindled cells within a fibromyxoid background are rarely observed. Differential diagnosis includes, but is not limited to, malignant neoplasms occurring at the same sites, in particular urothelial carcinoma with deceptively bland morphology (with small tubules, microcystic and nested variants), prostatic adenocarcinoma, and clear cell adenocarcinoma. Immunohistochemical studies with antibodies targeting members of the paired box gene family (PAX2 and/or PAX8) in NAs may be helpful in the differential diagnosis of urothelial lesions and prostatic adenocarcinoma. NAs are most likely to be confused with clear cell adenocarcinoma, especially in small biopsy specimens. This is confounded by both lesions being frequently positive for PAX2, PAX8, and CK7 and not infrequently positive for p504S (α-methylacyl-CoA-racemase, AMACR) by immunohistochemistry. Recognition of its characteristic morphological patterns and awareness of its unusual architectural and cytological features are important in making the diagnosis of NA and distinguishing this lesion from its mimickers.

Mammary Analogue Secretory Carcinoma: The First Submandibular Case Reported Including Findings on Fine Needle Aspiration Cytology

We present the first case (male, 35years old) of a mammary analogue secretory carcinoma occurring in a submandibular gland and document findings on fine needle aspiration cytology. On histology, the tumor displayed characteristic features: circumscribed nodules composed of bland, pink to light red neoplastic cells with low proliferative/mitotic activity arranged in tubular, vaguely cribriform, and microcystic structures containing Periodic acid Schiff-positive, diastase-resistant secretory material. Immunohistochemistry showed strong and diffuse positivity for cytokeratin 7, S100 protein, and vimentin, as well as moderate to strong immunoreactivity for c-kit in the majority of tumor cells. A rearrangement of the ETV6 gene on fluorescence in situ hybridization was documented. The patient underwent an ipsilateral selective (levels I-IV) neck dissection which showed metastasis in 3 out of 36 lymph nodes (levels 1-3). Adjuvant radiotherapy was administered. No local recurrence or metastatic disease has been detected during a follow up period of 28months.

Abstract 2417: A new mouse model for epithelial ear neoplasms based upon expression of mutant EGFRL858R/T790M

Abstract Epithelial neoplasms of the ear are rare and difficult to detect before the development of audiovestibular or facial nerve dysfunction. Complete resection is often difficult because of location and the late stage at diagnosis, so effective chemotherapy is required. No preclinical models exist for these tumors. During the generation of mice using CC10 or surfactant protein C (SP-C) promoters to drive expression of mutant EGFR (EGFRL858R/T790M) in lung tissues, we observed that no SP-C mice developed lung tumors, but approximately 30% of them developed head tilt and a circular gait by 25 wk. MRI scans showed bilateral ear tumors located in the tympanic cavity that partially invaded into temporal bone, which suggested the presence of middle ear tumors or endolymphatic sac tumors (ELSTs). Histology of the ear tumors showed well-differentiated adenocarcinomas with multiple papillary and microcystic structures. Immunohistochemical (IHC) analysis showed that the mutant EGFR was active and selectively expressed in the tumors, and that downstream components of EGFR signaling such as Akt, mTOR and ERK were activated. SP-C expression was also detected, suggesting that surfactant proteins are expressed in ear epithelium at specific times during tumor development. To determine if these tumors were addicted to EGFR signaling, EGFR-based therapies were tested in symptomatic mice. Consistent with the T790M mutation in EGFR conferring resistance to reversible EGFR tyrosine kinase inhibitors (TKI), erlotinib was ineffective. In contrast, the combination of an irreversible EGFR TKI (BIBW-2992) with an antibody against EGFR (cetuximab), or a chemically optimized analogue of BIBW-2992 (WZ4002) used alone, was highly effective. All mice treated with the combination or WZ4002 alone had normalization of gait and complete responses by MRI, suggesting that these tumors are dependent upon mutant EGFR. To assess the possible clinical relevance of this mouse model, 2 human middle ear adenocarcinomas and a human ELST were stained for active EGFR using IHC. 3/3 displayed increased EGFR activation. These studies describe a new mouse model for human epithelial ear tumors based on EGFR activation, and raise the possibility that EGFR-based therapies might have clinical efficacy in these rare neoplasms. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2417. doi:10.1158/1538-7445.AM2011-2417

In Vivo Fluorescence Mode Confocal Microscopy of Subepithelial Tissues in Glaucoma Filtering Blebs

The miniaturization of confocal imaging technology has resulted in the development of a handheld confocal microscope probe capable of fluorescence mode imaging. Findings in the subepithelial tissues of glaucoma filtering blebs using this novel approach for proof of concept are described. A fiberoptic confocal imaging probe using an illumination wavelength of 488 nm was applied to the bleb surface of 11 eyes after topical or subconjunctival administration of sodium fluorescein. The imaging plane was moved to the subepithelial region and multiple images from multiple bleb regions were captured at a resolution of 1,024 x 1,024 pixels per square inch. High-quality images of the bleb wall structure, vasculature, and superficial sclera were obtained and demonstrated subcellular detail. Lateral resolution was between 1 and 1.5 microm and axial resolution was approximately 30 microm. Identifiable structures in the failing blebs included vasculature (including individual erythrocytes, pericytes, and vascular endothelium); microcystic structures; and cells within the Tenon's tissue, some of which resembled fibroblasts. Fluorescence mode imaging of ocular subsurface detail is a viable and promising tool for assessment of wound healing and other processes in trabeculectomy blebs. The ability to image fluorophores creates the possibility of functional imaging.

Pituitary Enlargement in Patients with PROP1 Gene Inactivating Mutation Represents Cystic Hyperplasia of the Intermediate Pituitary Lobe. Histopathology and Over 10 Years Follow-up of Two Patients

Patients with a PROP1 inactivating mutation present combined pituitary hormone deficiency (CPHD) and pituitary maldevelopment. A retrospective analysis of 31 CPHD patients with a PROP1 mutation revealed two individuals, aged 18 and 4.5 years, who had undergone subtotal surgery to remove pituitary tumors, 16.8 x 12 mm and 9 x 10 x 12 mm in size. Histological reassessment of tissue samples revealed epithelial cells, partially oxyphilic, forming gland-like microcystic structures, most of them filled with eosinophilic colloid. These structures were directly linked with fragments of the posterior lobe. Neither atypia nor any traces of proliferation activity (Ki-67 LI=0%) were noted. Immunohistochemistry showed the presence of all hormonal phenotypes of cells. These findings corresponded to the intermediate lobe of the pituitary gland. For this type of pathology we propose the term 'cystic hyperplasia of the intermediate pituitary lobe' and suggest PROP1 gene assessment in patients with CPHD in order to avoid unnecessary neurosurgical interventions.

Cervical thymoma originating in ectopic thymic tissue in a cat

An 11-year-old female spayed domestic shorthair cat was referred to The Ohio State University Veterinary Teaching Hospital (OSU-VTH) for evaluation of a 6 x 4 x 3.5 cm mass in the left midcervical region causing increased respiratory sounds and lateral deviation of the trachea. A fine needle aspirate of the mass was obtained before referral and the cytology results were compatible with a reactive lymph node. Immunocytochemistry showed increased numbers of CD3+ T lymphocytes and small numbers of CD20+ and CD79a+ medium to large lymphocytes. Differential diagnoses from the referral pathologist were T-cell-rich B-cell lymphoma and feline Hodgkin's-like lymphoma. A subsequent fine needle aspirate performed at the OSU-VTH showed similar results. On flow cytometry the majority of cells were CD3+ T lymphocytes that were double positive for CD4 and CD8 (73%), compatible with either a double-positive (CD4+CD8+) T-cell lymphoma or lymphocytes from ectopic thymic tissue. The mass was surgically removed. Histopathology and immunohistochemistry of the mass revealed a predominant population of CD3+ small lymphocytes and small numbers of medium to large lymphocytes with moderate anisocytosis and anysokaryosis. A population of cytokeratin-positive epithelial cells surrounded small microcystic structures filled with eosinophilic material and structures interpreted as Hassall's corpuscles. These findings were consistent with thymic tissue and a diagnosis of ectopic thymoma was made. PCR results for lymphocyte antigen receptor rearrangement (PARR) were negative. The cat had no evidence of disease 16 months after removal of the mass. To our knowledge this is the first report of an ectopic cervical thymoma in a cat. The clinical and diagnostic features of this unusual case will be useful in helping veterinarians and pathologists obtain a presurgical diagnosis and establish a prognosis for similar lesions.

Adenomatoid tumour of the liver

An unusual primary adenomatoid tumour arising in the normal liver is described. Hepatectomy was performed, and the patient is alive and free of disease 1 year postsurgery. Grossly, the tumour...

Epithelial Marker–Negative Desmoplastic Small Round Cell Tumor With Atypical Morphology: Definitive Classification by Fluorescence In Situ Hybridization

Desmoplastic small round cell tumor typically presents with abundant desmoplastic stroma containing nested primitive round cells bearing a polyphenotypic immunohistochemical profile. Lesions with minimal classic morphology pose a formidable diagnostic challenge. The current case represents one such example, arising as a large abdominal-pelvic mass in a 17-year-old female patient. The tumor was composed of a monomorphous population of small round cells lining microcystic structures and forming pseudoacini and fine anastomosing trabeculae and cords. The stroma was abundantly myxoid with only occasional thick desmoplastic septa. The tumor cells were variably immunopositive for vimentin, desmin, smooth muscle actin, synaptophysin, neuron-specific enolase, Bcl-2 and WT1 (nuclear); epithelial markers were negative. The definitive diagnosis of desmoplastic small round cell tumor was rendered with the demonstration of the characteristic EWS-WT1 gene fusion by fluorescence in situ hybridization. The current case emphasizes the utility of fluorescence in situ hybridization to demonstrate EWS-WT1 gene fusion in desmoplastic small round cell tumor with nonclassic morphologic and immunohistochemical features to avoid potential misdiagnosis.