Yee Lin Tang

Discovered on gastrointestinal stromal tumours 1 (DOG1) expression in non-gastrointestinal stromal tumour (non-GIST) neoplasms

Mertens F. FUS–CREB3 l2/l1-positive sarcomas show a specific gene expression profile with upregulation of CD24 and FOXL1. Clin. Cancer Res. 2011; 17; 2646–2656. 9. Doyle LA, Moller E, Dal Cin P, Fletcher CD, Mertens F, Hornick JL. MUC4 is a highly sensitive and specific marker for low-grade fibromyxoid sarcoma. Am. J. Surg. Pathol. 2011; 35; 733–741. 10. Doyle LA, Hornick JL. EWSR1 rearrangements in sclerosing epithelioid fibrosarcoma. Am. J. Surg. Pathol. 2013; 37; 1630– 1631. 11. Arbajian E, Puls F, Magnusson L et al. Recurrent EWSR1– CREB3 l1 gene fusions in sclerosing epithelioid fibrosarcoma. Am. J. Surg. Pathol. 2014; [Epub ahead of print].

Extradural Brain Mass in a 64-Year-Old Man: Correspondence

A 64-year-old male Chinese patient presented with generalized tonic-clonic seizures for a month prior to admission. He had a past history of diabetes, hypertension and previous cerebrovascular accident. Otherwise, he had no other constitutional symptoms such as fever, chills, weight loss etc. Physical examination did not disclose any systemic lymphadenopathy. Subsequent MRI revealed right frontal extra-axial mass with features suggestive of a meningioma which was associated with compression of the anterior portion of the superior sagittal sinus (Figure 1A). He underwent a craniotomy and tumor excision. During surgery, an avascular right frontal enplaque tumor associated with poor brain-tumor interface was noted. A biopsy of the mass was submitted for frozen section intraoperative consultation during which smears as well as frozen tissue sections were prepared. Following the frozen section result, a subtotal resection was undertaken with residual tumor remaining in the patient. PATHOLOGICAL FINDINGS

The impersonator of gastric malt lymphoma: A tale of a T-Cell lymphoma with CD20 expression

We present a case of a 54-year-old Chinese female with no known medical history presenting with epigastric pain. The biopsies revealed expansion of the lamina propria by dense lymphoplas-macytic infiltrate comprising small lymphocytes with clear cytoplasm, forming lymphoepithelial lesions. The initial morphological impression was that of an extranodal marginal zone lymphoma (MALT); however, the concomitant expression of CD20 and CD3 in the abnormal lymphocytes was unusual, prompting additional workup which showed CD2, CD5 and CD8 positivity in the tumour cells without Pax5 expression. Polymerase chain reaction revealed monoclonal T-cell receptor gene rearrangement and the absence of a clonal immunoglobulin heavy chain (IgH) gene rearrangement, thus confirming the T-cell phe-notype of the neoplastic lymphocytes. As peripheral T-cell lymphoma may display myriads of morphological appearance and is generally associated with a poorer prognosis as compared to a low grade B-cell lymphoma such as MALT lymphoma, awareness of its ability to aberrantly express B cell phenotype such as CD19, CD20 and CD79a is pivotal in preventing a misdiagnosis. In such an instance, a judicious application of a panel of immunohistochemistry stains in conjunction with molecular studies will assist in establishing the correct diagnosis.

A 58 Year-Old Male with Hallucinations and Ataxia

A 58 year old Caucasian male presented with weight and appetite loss over 2 to 3 months. He was recently diagnosed with HIV infection. His initial CD4 count was < 20 cells/mm (7%) with a viral load of 352000 copies/ml. He was started on highly active antiretroviral therapy (HAART) and in the third month of therapy, he presented with increasing hallucinations and ataxia. Serologies for hepatitisA, hepatitis B, CMV, toxoplasma, syphilis, tuberculosis (TB) and Cryptococcus neoformans were negative. His CSF profile was negative for Cryptococcus neoformans, TB, HSV, CMV, toxoplasma, VZV and EBV were negative. In addition, his CD4 count rose to 202 cells/mm with a viral load of 425 copies/ml. MRI showed an area of heterogeneous contrast enhancement affecting the deep nuclei as well as white and grey matter tracts with extension into the deep white matter of the right frontal, temporal and parietal lobes. This area exhibited mild mass effect compressing on the left lateral and third ventricles with early midline shift to the left (Fig. 1a). In view of the radiological findings, a clinical diagnosis of lymphoma was considered and the patient underwent a brain biopsy to ascertain the nature of the brain lesion.

Epithelial misplacement in the gastrointestinal tract: a diagnostic pitfall revisited in a patient with peutz jegher’s syndrome

Epithelial misplacement or ‘pseudoinvasion’ is a known phenomenon occurring in the gastrointestinal tract that may potentially result in the misdiagnosis of a malignancy, particularly to the uninitiated. Recent papers indicated that similar diagnostic dilemmas occur in the breast and thyroid tissues, usually following a biopsy procedure. In the gastrointestinal tract, the epithelial displacement is thought to result from herniation of the mucosa through defects of the muscularis mucosae and propria secondary to trauma from medical procedures or due to the inherent peristaltic action. We detail an instance where epithelial misplacement in a hamar-tomatous polyp in the ileum affecting a 17-year-old Malay man with Peutz-Jeghers syndrome raised the concern for malignancy. The patient had undergone a subtotal colectomy with extended ileal resection following intussusception. The resected specimen revealed multiple hamartomatous polyps in the small bowel and caecum. On histology, one polyp disclosed the presence of mucosa and mucinous pools in the adipose tissue of the serosal layer which abut the peritoneal surface, mimicking an adenocarcinoma with mucinous features. The criteria and immunohistochemical stains acting as adjuncts for separating ‘pseudoinvasion’ occurring in the various types of gastrointestinal polyp including those with dys-plasia from an adenocarcinoma are presented.

40. Immune reconstitution inflammatory syndrome associated with JC virus infection: brain biopsy findings of a patient

Background and Method The immune reconstitution inflammatory syndrome (IRIS) in the setting of HIV infection is a recently recognised clinical phenomenon resulting from restored immunity to various infectious or non-infectious agents upon initiation of highly active antiretroviral therapy (HAART). IRIS may be multi-systemic and characteristically presents with paradoxical clinical deterioration of a pre-existing condition or the emergence of a new condition after the initiation of HAART. The diagnosis is challenging and reports documenting brain biopsy findings are rare. We present a case report of a 58-year-old male who was recently diagnosed with HIV infection and started on HAART. Results and Conclusion The patient presented with rapidly progressive functional decline within 3 months of therapy. Serial magnetic resonance imaging (MRI) scans showed progression from no significant acute abnormalities to oedema and enhancing lesions of the deep white and grey matter of the frontal and parietal lobes, as well as the right side of the midbrain. As a diagnosis of lymphoma was considered clinically, a right frontal lobe biopsy was performed. On histology, the brain sample showed dense T lymphocytic infiltrate, smaller numbers of B lymphocytes and a prominent population of plasma cells. Reactive gliosis, micro-glial nodules and occasional bizarre astrocytes were seen. JC polyomavirus was detected both in the cerebrospinal fluid and the biopsy tissue. As a dense lymphoplasmacytic infiltrate cannot be attributed to JC virus infection alone, the picture was consistent with IRIS associated with JC virus infection. The awareness of IRIS as a potential mimic of lymphoproliferative disorders on histology can prevent diagnostic pitfalls especially during intra-operative consults.

Unusual immunophenotypic expressions of plasma cell neoplasm: a potential diagnostic pitfall

A histological diagnosis of a plasma cell neoplasm is usually straightforward. We highlight two instances where the diagnosis of a plasma cell neoplasm was challenging due to unusual immu-nophenotypic expressions of the tumour, potentially mimicking a lymphoma. In the first case, a 68-year-old man presented with a neoplasm affecting T3-T5 of the spinal cord. On histology, the excised tumour disclosed a proliferation of malignant plasma cells with diffuse CD20 and cyclin D1 expressions, simulating a mantle cell lymphoma. In the second case, a 67-year-old Chinese man presented with gastric and duodenal tumour nodules. Superficial biopsy of the nodules disclosed poorly preserved large neoplastic cells in the lamina propria which resembled lymphoid cells and stained for CD3. A diagnosis of myeloma was only apparent after correlation with the past history of a myeloma followed by a subsequent supraclavicular mass biopsy revealing better preserved plasma cells with similar CD3 expression. Awareness of the ability of neoplastic plasma cells in expressing both B and T cell antigens in addition to careful light microscopic examination, performance of a panel of immunohistochemistry stains and correlation with clinical history is pivotal in establishing the correct diagnosis.