Objectives To determine the clinical utility of assessment of tumour invasion, markers of proliferation, and the French clinicopathological classification in pituitary tumour prognostication. Methods This is a retrospective evaluation of adult patients undergoing pituitary surgery at Oxford University and St Vincent's Hospitals, between 1989 and 2016, with at least 12 months of clinical data. Invasion was assessed radiologically, proliferative markers (Ki67, mitotic count, p53) by immunohistochemistry. Tumours were graded according to the clinicopathological classification. Intra- and interlaboratory variability of histopathology reporting was evaluated. Outcomes (1) Tumour recurrence (radiological or reintervention & GE;12 months postoperatively) and/or (2) "aggressive behaviour" (& GE;4 interventions and/or invasive tumour with recurrence/reintervention between 12 and 24 months postoperatively). Results A total of 386 patients were included, age at surgery was 56 (interquartile range [IQR] 41-67) years, 54% were male, and median follow-up was 90 months (range 44-126). Tumours were predominantly clinically nonfunctioning (252, 65%), with overall 53% invasive, and 10% that demonstrated & GE;2 proliferative marker positivity. Recurrence was predicted by invasiveness (hazards ratio [HR] 1.6 [1.10-2.37], P .02), elevated mitotic count (HR 2.17 [1.21-3.89], P .01), grade (2b vs 1a HR 2.32 [1.06-5.03], P .03), and absence of gross total resection (HR 3.70 [1.72-8.00], P .01). Clinically defined aggressiveness was associated with elevated Ki67, mitotic count, and invasiveness. Ki67 reporting methodologies showed moderate correlation across laboratories (Phi 0.620), whereas p53 reporting reproducibility was poor (Phi 0.146). Conclusions Proliferative markers, including Ki67 and mitotic count, but not p53, are important in predicting the development of aggressive pituitary tumour behaviour.

Background: Calcifying fibrous pseudotumour is a benign mesenchymal tumour typically of the soft tissue but are also found in a variety of anatomic sites. These lesions are rare and are often composed of hyalinised collaged, psammamatous or dystrophic calcification and lymphocytic infiltration. Aim: To present a case of diagnostic interest. Method and results: We present a case of a 38-year-old male with CT confirmed uncomplicated acute appendicitis with a reported appendicolith. He underwent a laparoscopic appendicectomy, during which a 13x10x10mm nodule was identified on the mesenteric border of the terminal ileum and was excised completely. Histopathology confirmed acute suppurative appendicitis with no evidence of malignancy. The nodule showed a submesothelial densely sclerotic nodule with ossifications, plasmacytic infiltrates and patchy lymphoid cell stroma with occasional lymphoid follicles. No cellular spindled cell or epithelioid cell proliferation was seen. There was no abnormal proliferation of Cytokeratin, S-100 or CD117 positive cells. IgG4-positive plasma cells counting up to 40 were identified in a high-power-field. Discussion: The pathophysiology of calcified fibrous pseudotumour is not properly understood. It has been potentially associated with prior infections, trauma or surgery, and inflammatory conditions such as IgG4 mediated disease. Although these lesions are benign they can be diagnostically challenging, for example reported as an appendicolith. As incidental intra-abdominal nodules may be difficult to clinically differentiate intra-operatively, excisional biopsy confers immense diagnostic benefit as it is imperative to exclude aggressive or malignant soft tissue lesions such as desmoid tumours or sarcoma.

We report a case of a melanocytic naevus showing prominent pseudo-Dabska pattern on the back of a 25-year-old woman. The lesion has a pseudo-vascular appearance comprising multiple tortuous spaces within the dermis lined by SOX-10 positive naevus cells. The cells form pseudo-papillary projections and have a hobnail appearance similar to Dabska tumours. On immunohistochemistry the cells are negative for SMA, HMB-45 and ERG. Ki67 proliferation index is low. The Dabska tumour is a rare lymphovascular neoplasm occurring primarily in the paediatric population. Other lesions which have been reported to show a ‘pseudo-Dabska’ phenomenon include retiform haemangiomas (RH), early Kaposi sarcomas (KS), well differentiated angiosarcomas and acantholytic squamous cell carcinoma (ASCC) in the skin. The pseudo-Dabska pattern has only recently been described in melanocytic lesions. Knowledge of this pattern will facilitate prompt and accurate diagnosis of similar melanocytic tumours as well as other lesions with pseudo-Dabska architecture.

Abstract Objective: The clinical utility and prognostic value of WHO 2017 lineage-based classification of pituitary tumors have not been assessed. This study aimed to (1) To determine the clinical utility of transcription factor analysis for classification of pituitary tumors and (2) To determine the prognostic value of improved lineage-based classification of pituitary tumors. Methods: This was a retrospective evaluation of patients who underwent surgical resection of pituitary tumors at a tertiary referral centre between 1990 and 2016. Included patients were at least 18 years of age and had complete histopathological data, forming the “histological cohort”. Patients with at least 12 months of post-surgical follow up were included in the subgroup “clinical cohort”. The diagnostic efficacy of transcription factor immunohistochemistry in conjunction with hormone immunohistochemistry was compared with hormone immunohistochemistry alone. The prognostic value of identifying “higher risk” histological subtypes was assessed. Results: There were 172 patient tumor samples analyzed in the histological cohort. Of these, there were 96 patients forming the clinical cohort. Subtype diagnosis was changed in 24/172 (14%) of tumors. Within the clinical cohort, there were 21/96 (22%) patients identified with higher risk histological subtype tumors. These were associated with tumor invasiveness (p=0.032), early recurrence (12-24 months, p=0.016), shorter median time to recurrence (38 [IQR 20-68.5] v 15 [IQR 12-27.25] months, p=0.02) and reduced recurrence-free survival (p=0.023). Conclusions: Application of transcription factor analysis, in addition to hormone IHC, is associated with improved diagnostic information.

Background Post-transplant lymphoproliferative disorders (PTLD) are a heterogeneous group of lymphoid proliferations of varying clonal composition secondary to immunosuppression in solid-organ transplant. Most commonly are of B-cell in origin; T-cell lymphomas are rare (15% of all PTLD). Case presentation A 75-year-old man with 15-year post-heart transplant for dilated cardiomyopathy presented with a large left-sided pleural effusion. Pleural fluid cytology was highly cellular and contained dispersed large malignant cells having small to moderate amount of granular cytoplasm with pleomorphic nuclei and prominent nucleoli; many cells had multiple chromocentres; some were binucleate. Occasional mitoses and apoptotic bodies were present. Phenotypically, cells were positive for CD3, CD30, and EMA but negative for CD4, CD8, CD5 and CD7. They were negative for ALK and EBV markers. Flow cytometry showed positivity for T-cell and NK-cell markers (CD2, CD3, CD7, CD56, CD57 and TCR). Discussion Only a few cases of post-transplant T-cell lymphoma have been described in literature. To our knowledge, this is the first reported case of an ALK and EBV negative anaplastic T-cell lymphoma in pleural fluid cytology following cardiac transplant. Similar to B-cells proliferation, they have a predilection for skin, abdomen and pleura; only a minority are associated with EBV infection, in contrast to B-cells proliferation. The prognosis is generally poor. Post-transplant lymphoproliferative disorders (PTLD) are a heterogeneous group of lymphoid proliferations of varying clonal composition secondary to immunosuppression in solid-organ transplant. Most commonly are of B-cell in origin; T-cell lymphomas are rare (15% of all PTLD). A 75-year-old man with 15-year post-heart transplant for dilated cardiomyopathy presented with a large left-sided pleural effusion. Pleural fluid cytology was highly cellular and contained dispersed large malignant cells having small to moderate amount of granular cytoplasm with pleomorphic nuclei and prominent nucleoli; many cells had multiple chromocentres; some were binucleate. Occasional mitoses and apoptotic bodies were present. Phenotypically, cells were positive for CD3, CD30, and EMA but negative for CD4, CD8, CD5 and CD7. They were negative for ALK and EBV markers. Flow cytometry showed positivity for T-cell and NK-cell markers (CD2, CD3, CD7, CD56, CD57 and TCR). Only a few cases of post-transplant T-cell lymphoma have been described in literature. To our knowledge, this is the first reported case of an ALK and EBV negative anaplastic T-cell lymphoma in pleural fluid cytology following cardiac transplant. Similar to B-cells proliferation, they have a predilection for skin, abdomen and pleura; only a minority are associated with EBV infection, in contrast to B-cells proliferation. The prognosis is generally poor.

Aims Description of a rare case of cauda equina: Capillary haemangioma. Method Review of histopathology, imaging and literature. Result A 44-year-old lady presented with recent-onset left-sided low back pain radiating to anterior thigh. She had a back injury nine years prior; magnetic resonance imaging (MRI) then showed a low termination of spinal cord at L2/3 level and a small intraspinal lipoma. The recent MRI showed an intraspinal enhancing mass at L2/3 with nerve root displacement to the right. In light of significant progression in size over the nine-year period, the intradural red fleshy tumour adherent to multiple nerve roots of the cauda equina was subsequently removed. A 22 × 10 × 5 mm dark-brown lobulated tumour was received. Histologically, there was a circumscribed pseudoencapsulated CH arising within a substantial nerve trunk. Variably sized vascular spaces were arranged in lobular pattern and lined by bland endothelial cells (ERG-positive and S100-negative). Discussion CHs are commonly seen as cutaneous and mucosal lesions. CHs of the cauda equina are extremely rare and clinically simulate schwannoma, ependymoma, or neurofibroma. To our knowledge, only 19 cases have been previously described since publication of the earliest report in 1987. It should be considered as a differential diagnosis in middle-aged patients with enhancing lesions of the cauda equina. Description of a rare case of cauda equina: Capillary haemangioma. Review of histopathology, imaging and literature. A 44-year-old lady presented with recent-onset left-sided low back pain radiating to anterior thigh. She had a back injury nine years prior; magnetic resonance imaging (MRI) then showed a low termination of spinal cord at L2/3 level and a small intraspinal lipoma. The recent MRI showed an intraspinal enhancing mass at L2/3 with nerve root displacement to the right. In light of significant progression in size over the nine-year period, the intradural red fleshy tumour adherent to multiple nerve roots of the cauda equina was subsequently removed. A 22 × 10 × 5 mm dark-brown lobulated tumour was received. Histologically, there was a circumscribed pseudoencapsulated CH arising within a substantial nerve trunk. Variably sized vascular spaces were arranged in lobular pattern and lined by bland endothelial cells (ERG-positive and S100-negative). CHs are commonly seen as cutaneous and mucosal lesions. CHs of the cauda equina are extremely rare and clinically simulate schwannoma, ependymoma, or neurofibroma. To our knowledge, only 19 cases have been previously described since publication of the earliest report in 1987. It should be considered as a differential diagnosis in middle-aged patients with enhancing lesions of the cauda equina.

Background Follicular lymphoma (FL) is a predominantly nodal disease and extranodal involvement can be seen in widespread nodal disease. Primary extra-nodal FLs are, however, reported in skin, ocular adenexa, Waldeyer's ring and intestine where the majority are mucosa-associated-lymphoid-tissue (MALT) lymphoma and diffuse large B-cell lymphoma. Primary duodenal follicular lymphoma (FL-D) is a distinct mucosal/submucosal variant of FL. Case presentation A 44-year-old man presented with vomiting and subsequent endoscopic examination revealed small bubbly appearances in the first part of the duodenum. Three superficial duodenal mucosal biopsies showed preservation of the normal villous architecture; however, there was a prominent lymphoid infiltrate with prominent follicle formation within the lamina propria of the villi. Whilst CD3/CD5 positive T lymphocytes were present, the majority of the lymphoid cells, and the lymphoid cells forming the lymphoid follicles were positive for CD20, bcl2, bcl6 and CD10 and negative for cyclinD1; CD21 highlighted the follicular dendritic networks. Only very occasional centroblasts were noted within the lymphoid follicles, consistent with Grade-1 FL. Disscussion FL-D, first described in 1997, is a rare disease accounting for 1–3.6% of primary GIT lymphomas. FL-Ds are typically low grade. Transformation to high grade disease or systemic dissemination appears extremely uncommon. Follicular lymphoma (FL) is a predominantly nodal disease and extranodal involvement can be seen in widespread nodal disease. Primary extra-nodal FLs are, however, reported in skin, ocular adenexa, Waldeyer's ring and intestine where the majority are mucosa-associated-lymphoid-tissue (MALT) lymphoma and diffuse large B-cell lymphoma. Primary duodenal follicular lymphoma (FL-D) is a distinct mucosal/submucosal variant of FL. A 44-year-old man presented with vomiting and subsequent endoscopic examination revealed small bubbly appearances in the first part of the duodenum. Three superficial duodenal mucosal biopsies showed preservation of the normal villous architecture; however, there was a prominent lymphoid infiltrate with prominent follicle formation within the lamina propria of the villi. Whilst CD3/CD5 positive T lymphocytes were present, the majority of the lymphoid cells, and the lymphoid cells forming the lymphoid follicles were positive for CD20, bcl2, bcl6 and CD10 and negative for cyclinD1; CD21 highlighted the follicular dendritic networks. Only very occasional centroblasts were noted within the lymphoid follicles, consistent with Grade-1 FL. FL-D, first described in 1997, is a rare disease accounting for 1–3.6% of primary GIT lymphomas. FL-Ds are typically low grade. Transformation to high grade disease or systemic dissemination appears extremely uncommon.