[Q Fever Endocarditis-Associated Immune Complex-Mediated Proliferative Glomerulonephritis: Fourth Case from Türkiye]. / Q Atesi Endokarditi Iliskili Immün Kompleks Aracili Proliferatif Glomerülonefrit: Türkiye'den Dördüncü Olgu.

Q fever is a zoonosis caused by the intracellular gram-negative bacterium Coxiella burnetii. Infection can be asymptomatic, acute or can cause chronic disease. Chronic disease often presents with infective endocarditis (IE). Diagnosis of IE is difficult because the agent does not grow easily in standard blood cultures and valve vegetations are difficult to detect. Glomerular involvement in patients with Q fever endocarditis is limited to the case reports. In addition, a total of three cases of Q fever endocarditis from Türkiye have been published so far. In this case report, a fourth case of Q fever endocarditis from Türkiye accompanied by immune complex-mediated glomerulonephritis was presented. A 35-year-old male patient with a history of mitral and aortic heart valve replacement was admitted with complaints of fever, night sweats and involuntary weight loss. Cervical lymphadenopathy and hepatosplenomegaly were found during the examination. Laboratory investigations revealed anemia inflammation, acute kidney injury (AKI), hematuria and proteinuria. While no causative agent was detected in blood and urine cultures, no diagnosis could be made as a result of bone marrow and cervical lymph node biopsies.Transesophageal echocardiography was performed for the etiology of fever and revealed 7 mm vegetation on the prosthetic mitral valve. C.burnetii phase 1 IgG tested with indirect immunofluorescent antibody method was reported positive at 1/16384 titer and doxycycline and hydroxychloroquine treatments were initiated. Kidney biopsy for the etiology of AKI revealed focal segmental endocapillary proliferative glomerulonephritis with C3, C1q and IgM immunocomplex deposition. After the addition of methylprednisolone to the treatment, the patient's symptoms improved and creatinine and proteinuria levels decreased dramatically. Although Q fever is endemic in our country, it is detected in fewer numbers than expected. In addition to the difficulties in microbiological and clinical diagnosis, the low awareness of physicians about the disease is one of the important reasons for this situation. When the disease comes to mind, the diagnosis can be easily reached by serological methods. Therefore, Q fever should be investigated in the presence of lymphoproliferative disease-like findings fever of unknown origin and culture-negative endocarditis.

Comprehensive assessment and outcomes of patients with chronic periaortitis.

OBJECTIVES: Chronic periaortitis (CP) is a less known but more frequently diagnosed fibro-inflammatory disorder, but we know little about it and data regarding follow-up and outcome are still very limited. This study aims to identify the clinicopathologic, laboratory, and radiologic features, as well as outcomes of CP patients. METHODS: Patients with CP from HUVAC database were included in the study. CP was diagnosed based on compatible imaging findings and histopathological evaluation (if available), in addition to clinical findings. Demographics, laboratory, clinical, and imaging data were retrospectively reviewed from medical records. RESULTS: A total of 51 (male/female:37/14) patients were included in the study. Median (IQR) age was 63 (53-69) years and follow-up duration was 40 (4-60) months. 32 of the patients were IgG4-related CP. The most common form of CP in our cohort was idiopathic retroperitoneal fibrosis (82%), followed by inflammatory abdominal aortic aneurysms (12%) and peri-aneurysmal retroperitoneal fibrosis (8%). 8 (15.6%) patients had thoracic periaortitis and 16 (31.6%) venous involvement. Cyclophosphamide (CYC) combined with steroids was the most preferred treatment modality (43%), followed by rituximab (RTX) (31.3%). Follow-up imaging was done after a median (IQR) of 7(3-11) months, 30% of the patients were stable and 64.1% showed regression. A total of 18 (35.2%) had been taken off therapy at the last visit. CONCLUSIONS: Idiopathic retroperitoneal fibrosis was the most frequent presentation, whereas 15.6% of patients had thoracic involvement. Venous involvement was also not uncommon. Optimal time for follow-up imaging was determined as 6-9 months. Steroids along with CYC/RTX had a favourable outcome in the treatment of these patients.

Clonal B-cell proliferations developing in the background of primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder: A case series.

Clonal B-cell proliferations and B-cell lymphomas may co-occur in the background of follicular helper T-cell (TFH)-derived lymphomas, most associated with EBV, which has been a well-known fact for many years in the prototypical entity "TFH lymphoma, angioimmunoblastic-type." Primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder (CD4+ PCSM-LPD) is also a TFH-derived clonal proliferation. We searched the archives and identified four cases of CD4+ PCSM-LPD with accompanying clonal B-cell proliferation (one of which showed EBER positivity), and one longstanding case of CD4+ PCSM-LPD, in the background of which a B-cell lymphoma had developed. These five cases broaden experience on CD4+ PCSM-LPD with accompanying B-cell proliferations and also support routine evaluation of these cases with EBV in situ hybridization, to better determine whether or not there is an association with EBV.

Diffuse Large B-Cell Lymphoma, Epstein-Barr Virus -Positive Kappa Monotypic Plasma Cell Proliferation and Invasive Carcinoma, Developing in a Child With Defective Mismatch Repair.

Constitutional mismatch repair deficiency (CMMRD) syndrome is characterized by biallelic mutations in a mismatch repair gene and is associated with development of childhood cancers and symptoms resembling neurofibromatosis type 1, like café-au-lait spots. We describe the extremely rare case of a 12-year-old male presenting with several light brown macular lesions on the skin, gastrointestinal diffuse large B-cell lymphoma, adenomatous polyposis throughout the gastrointestinal tract and an intra-abdominal invasive carcinoma derived from upper gastrointestinal system. All neoplasia, as well as normal tissues, showed loss of Msh6 expression with immunohistochemistry. Molecular studies showed pathogenic homozygous p.F1088Sfs*2 mutation in MSH6. Furthermore, signs consistent with immunodeficiency, namely decreased levels of IgG and IgA in the serum, nodular lymphoid hyperplasia and EBV-associated plasma cell proliferation with monotypic kappa light chain expression in the ileum, were also noted. Our case depicts the phenotypic diversity of CMMRD syndrome and emphasizes its association with immunodeficiency, raising awareness to a feature not widely recognized.

Significance of caveolin-1 immunohistochemical staining differences in biopsy samples from kidney recipients with BK virus viremia.

BK virus infections which usually remains asymptomatic in healthy adults may have different clinical manifestations in immunocompromised patient population. BK virus reactivation can cause BK virus nephropathy in 8% of kidney transplant patients and graft loss may be seen if not treated. Clathrin or Caveolar system is known to be required for the transport of many viruses from Polyomaviruses family including BK viruses. In this study, kidney transplant patients with BK virus viremia were divided into two groups according to the BK virus nephropathy found in kidney biopsy (Group I: Viremia+, Nephropathy+ / Group II: Viremia+, Nephropathy-). Kidney biopsies were examined with immunohistochemical staining to determine the distribution and density of the Caveolin-1 and Clathrin molecules. Immunohistochemical staining of the 31 pathologic specimens with anti-caveolin-1 immunoglobulin revealed statistically significant difference between group-I and group-II. The number of the specimens stained with anti-caveolin-1 was less in group I. On the other hand, we did not find any difference between the groups regarding the anti-clathrin immunochemical analysis. According to these findings, caveolin-1 expression differences in kidney transplant patients may be important in disease progression.

Distribution of lymphomas in Turkey: data of 4239 cases from a single institution using the WHO classification

Background/aim: Lymphoma cases diagnosed at one of the largest tertiary reference centers in Turkey were reviewed and findings were compared to those reported from other regions of the world. Materials and methods: Lymphomas diagnosed between 2000 and 2017 in the pathology laboratory of Hacettepe University were identified. A total of 4239 cases were analyzed. The WHO 2008 classification was used. Results: Hodgkin lymphomas accounted for almost 20% of cases. T-cell lymphomas were much more frequent (23% of our non- Hodgkin lymphoma (NHL) cases) in comparison to all other regions of the world. The reason for this difference was the high frequency of mycosis fungoides (MF) cases. We had significantly more cases of high-grade B-cell lymphoma (43.9% of NHLs) and fewer cases of low-grade B-cell lymphoma (33.5% of NHLs) in comparison to the rates of developed regions of the world and the reverse was true when compared to developing parts of the world. Burkitt lymphoma frequency (4% of NHLs) was also higher than in most parts of the world. Conclusion: Our data reveal that the frequency of MF, Burkitt lymphoma, and Hodgkin lymphoma are considerably higher, whereas follicular lymphoma rates are considerably lower than in most other parts of the world.

Atypical teratoid rhabdoid tumor arising in a pleomorphic xanthoastrocytoma: a rare entity.

Atypical teratoid rhabdoid tumor (AT/RT) is a rare and aggressive tumor usually occurring at younger ages. Pleomorphic xanthoastrocytomas (PXA) on the other hand are quiescent tumors with benign behavior. AT/RTs arising in the setting of PXA are exceptional. We present the case of a 23-year-old female patient, the fourth in the literature, speculated as having AT/RT arising within a PXA, as demonstrated by the presence of INI1 mutation. The patient presented with a short history of headache, which increased over time, and emerging seizures. She had a contrast-enhancing mass in the left temporal area demonstrated by MRI. Pathological examination demonstrated a dimorphic tumor containing a spindle-pleomorphic component reminiscent of PXA and a rhabdoid component with INI1 loss showing features of AT/RT. Both components shared the same BRAF mutation, supporting their common origin, and hence the case was speculated as an AT/RT arising in the setting of a PXA by secondary genetic change of inactivation of INI1. She had a poor outcome despite surgery and died 8 months after her diagnosis.
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Pituitary adenoma with gangliocytic component: report of 5 cases with focus on immunoprofile of gangliocytic component.

INTRODUCTION: Pituitary adenomas with gangliocytic component are rare tumors of the sellar region that are composed of pituitary adenoma cells and a ganglion cell component. Their histogenesis and hence nosology is not yet resolved because of the small number of cases reported and lack of large series in the literature. METHODS: Herein we report five cases of pituitary adenoma with gangliocytic component to add knowledge to this rare neoplasm. RESULTS: Three cases are functional mammosomatotroph adenomas, one case is functional sparsely granulated somatotroph adenoma and the other is functional corticotroph adenoma. Gangliocytic component showed immunohistochemical expression of hormones in three cases. The ganglion cells were prolactin immunoreactive in case 1, GH and TSH immunoreactive in case 5 and showed expression of prolactin, TSH, ACTH and FSH in case 4. Three cases had undergone more than one surgery of which two had gangliocytic cells only in the recurrent tumors whereas the third case showed gangliocytic cells only in the initial tumor. DISCUSSION: The cases are discussed with clinical and histological features and a brief review of the literature considering the histogenesis is included.

Pontine Rosai-Dorfman disease in a child.

INTRODUCTION: Rosai-Dorfman Disease (RDD) is a benign histiocytic disorder that commonly presents with massive lymphadenopathy. Central nervous system (CNS) involvement is only 5%; isolated CNS involvement is much rarer. The patient presented here has been diagnosed with isolated pontine RDD. CASE REPORT: A 5-year-old child was admitted to the hospital with the history of double vision and ptosis of the left eye. Magnetic resonance imaging revealed presence of a mass at the pontomesencephalic junction. Subtotal tumor excision was performed. Microscopic examination of the lesion showed histologic features consistent with RDD. The patient was followed up without medication, with a small residue. CONCLUSION: RDD is rare in childhood, and isolated CNS involvement is also quite rare. The tumor is located in pons in our case. The treatment of choice is gross total resection. Even total excision is not possible, follow up without medication may be an option because of the indolent and self-limited course of the disease.

Tip lesion variant of primary focal and segmental glomerulosclerosis: clinicopathological analysis of 20 cases.

The glomerular tip lesion (GTL) is a distinctive histopathologic lesion which is regarded as a variant of focal and segmental glomerulosclerosis (FSGS). The prognostic significance of GTL among other FSGS variants has been disputed. In order to define the clinical features and outcome of GTL, we retrospectively reviewed the presenting clinical features, laboratory and biopsy findings and surveillance in our cohort of GTL, which consisted of 20 adults with native kidneys (mean age 46 years) with follow-up data ranging from 3 to 137 months. At presentation, mean urine protein, serum albumin and cholesterol levels were 5.17 g/d, 2.6 g/dL and 312.9 mg/dL, respectively, and none had renal insufficiency. Microscopic hematuria was detected in five patients. At biopsy, glomerular segmental lesions consisted of GTL without perihilar or collapsing lesions. GTL was observed in a variable proportion of glomeruli from 2.6% to 100%. Mesangial proliferation was seen in nine cases, at a moderate degree in two and mild in the rest. Three biopsies showed mild, two showed moderate interstitial fibrosis/tubular atrophy. Eleven patients received steroids alone and eight received sequential therapy with steroids and a cytotoxic agent. At a mean follow-up of 40.6 months, 17 patients (85%) achieved complete remission of nephrotic syndrome, 15% had partial remission. Four of 17 suffered from recurrences. No patient progressed to end-stage renal disease. Serum albumin at diagnosis was the only predictor of a recurrence (p = 0.037). Microscopic hematuria correlated with incomplete remission (p = 0.045). Our study demonstrates a clearly favorable prognosis in patients with FSGS-GTL variant.

Is it Possible to Obtain Immunofluorescence Data in Formalin-Fixed Paraffin-Embedded Skin Samples for the Diagnosis of Pemphigus Vulgaris and Bullous Pemphigoid.

OBJECTIVE: The gold-standard method for assessment of autoimmune bullous disease is direct/indirect immunofluorescence (IF) examination applied to fresh frozen tissue. Since the sensitivity of IF is greatly reduced in formalin-fixed paraffin-embedded (FFPE) tissues, IF cannot be relied upon in these samples. However, immunohistochemistry with the C4d antibody is a promising marker used as a surrogate for immune complex deposition, in nephropathology practice, and the paraffin IF method is also used as a `salvage` technique when fresh frozen tissue is not available or lacks glomeruli. We aimed to investigate whether it is possible to obtain immunofluorescence data from FFPE tissues diagnosed with bullous pemphigoid (BP) and pemphigus vulgaris (PV) and its relationship with inflammatory parameters in the skin. MATERIAL AND METHODS: Eighty-nine in-house cases with both IgG and C3 positivity by routine immunofluorescence examination were included in the study. Inflammation parameters were evaluated in hematoxylin-eosin sections. Immunofluorescence study with IgG protease digestion and C4d immunohistochemistry were performed. RESULTS: Results of 83 biopsies were obtained by paraffin immunofluorescence with IgG. There were positive reactions in 28 (34%) of these 83 biopsies. Five of the 28 positive results belonged to BP (18%), and 23 were PV (82%). Ten positive results were on lesional skin (36%), and 18 (64%) were on non-lesional skin. In the immunohistochemical study with C4d, 84 biopsy results were obtained. There were positive reactions in 34 (40.4%) of 84 biopsies. Of the 34 positive results, 12 belonged to BP (35.3%) and 22 to PV (64.7%). Again, 22 (64.7%) of 34 positive results belonged to lesional skin, and 12 (35.3%) belonged to non-lesional skin. When both techniques were used together, 44 (54%) of 81 biopsies yielded positive results for at least one of the two studies, while in 37 (46%), both tests showed negative results. CONCLUSION: The sensitivity of both IgG and C4d was less than in the literature, especially in BP-diagnosed biopsies. Positive samples were mostly PV. In conclusion, obtaining immunofluorescence data in FFPE samples is possible and is independent of the related skin being lesional or not, however, negative results should not be relied upon.

Indolent B-cell non-Hodgkin lymphomas in children: high association with inborn errors of immunity.

Indolent lymphomas are rare in children and mostly consist of pediatric type follicular (PTFL) and pediatric marginal zone lymphomas (PMZL) and extranodal marginal zone lymphoma (ENMZL). Twenty children with indolent lymphoma (10 PTFL, 6 PMZL, 3 ENMZL, 1 mixed type) among 307 Non-Hodgkin Lymphoma (NHL) were retrospectively evaluated. The mean age of the entire group was 10.4 ± 4.4 and was significantly lower in PTFL than in PMZL. Seven patients (35%) had an associated inborn error of immunity (IEI) which was higher than that seen in aggressive lymphomas (5.9%) (p < 0.0001). Seventeen patients (85%) had stage I/II disease. Two patients received no treatment after surgery. Eleven patients were treated only with 3-6 courses of rituximab. Four patients received 3-6 courses of R-CHOP protocol. The prognosis was excellent Five years overall and event-free survivals were 100% and 85%, respectively.

Cytoplasmic WT1 in IgA nephropathy, an indicator of poor prognosis associated with mesangial/peri-mesangial C4d.

BACKGROUND: We aimed to investigate the immuno-histochemical expression of C4d, ADAM10 and WT1 in kidney biopsies of immunoglobulin A nephropathy (IgAN) patients and correlate the findings with clinical, laboratory and histopathologic features in the hope of defining new parameters to better understand the pathogenesis of the disease, and predict prognosis. MATERIALS AND METHODS: Paraffin-embedded kidney biopsy samples of 128 IgAN patients were immuno-histochemically treated with C4d and ADAM10/WT1 dual stain. Results were evaluated according to Oxford classification parameters, epidemiologic features, laboratory findings at presentation and clinical follow-up. RESULTS: We observed C4d positivity in 40.6% of our patients, 25% of which was mesangial/peri-mesangial (m/pm) staining. Only m/pmC4d positivity statistically correlated with progression to end-stage renal disease (ESRD). M/pmC4d positive patients had statistically significantly higher baseline proteinuria levels, presence of crescents and > 25% segmental sclerosis of glomeruli. There was cytoplasmic staining of WT1 in 11.2% of cases. Presence of cWT1 correlated with m/pmC4d positivity and progression to ESRD. There was no glomerular ADAM10 detected and tubular expression of this protein did not relate to amount of tubular damage or other parameters. CONCLUSION: This study is the first to show that cWT1is involved in IgAN and appears as an independent variable for worse prognosis.

Splenic Gaucheroma Leading to Incidental Diagnosis of Gaucher Disease in a 46-Year-Old Man with a Rare GBA Mutation: A Case Report.

BACKGROUND: Gaucher disease is a common lysosomal storage disease caused by the deficiency of the ß-glucosidase enzyme, leading to sphingolipid accumulation in the reticuloendothelial system in Gaucher cells. Clinical findings are quite variable and some patients may remain asymptomatic lifelong. However, even when patients have mild symptoms, there is a significant increase in their quality of life with enzyme replacement therapy. We aimed to reveal the relationship between a rare mutation in the Glucosylceramidase Beta (GBA) gene and clinical signs and symptoms. Another aim of the study was to show the effect of enzyme replacement therapy on the quality of life, even in patients with mild symptoms. CASE PRESENTATION: Here, we report a 46-year-old male diagnosed with Gaucher disease based on splenic Gaucheromas incidentally discovered in a cardiac computerized tomography scan. In GBA gene analysis, the extremely rare R87W mutation was detected in a homozygous state. In retrospect, the patient had nonspecific symptoms such as fatigue and bone pain for a long time, which were substantially ameliorated by enzyme replacement therapy. CONCLUSION: In patients with adult-onset Gaucher disease, the symptoms may be mild, causing significant diagnostic delay. Gaucher disease may be included in the differential diagnosis of abdominal malignancies. Early diagnosis and treatment can improve quality of life and prevent unnecessary procedures.

IgG4-related pachymeningitis-Long term follow up and outcome of six patients.

OBJECTIVE: Our understanding of IgG4-RD and pachymeningitis has grown substantially, but the optimal approach for diagnosis, management, and long-term outcomes is still an area of uncertainty. METHODS: HUVAC is a database for IgG4-RD patients, this database was retrospectively evaluated for pachymeningeal disease. Demographic, clinical, serological, imaging, histopathological data, and treatment details were re-interpreted in patients with pachymeningitis. RESULTS: Among 97 patients with IgG4-RD, 6 (6.2%) had pachymeningitis. None of these patients had extracranial features, and also, in most of the patients, serum IgG4 levels were normal. Tentorium cerebelli and transverse sinus dura were the most commonly involved in the posterior fossa. During 18 months of median follow-up on steroid+-rituximab, none of them relapsed as pachymeningitis. CONCLUSION: Our patients were mainly older males with sole neurological involvement. Non-specific headache was the most common manifestation, and serum IgG4 levels were not useful for diagnosis. Typical radiology and tentorial thickening should suggest IgG4-RD and prompt an early biopsy. Moreover, accompanying hypophysitis could also be a clue. With steroids+ rituximab treatment, no relapse related to meningeal involvement was seen in long-term follow-up.

Copy Number Loss at Chromosome 14q11.2 Correlates With the Proportion of T Cells in Biopsies and Helps Identify T-Cell Neoplasms.

CONTEXT.­: Evidence of T-cell clonality is often critical in supporting the diagnosis of a T-cell lymphoma. OBJECTIVES.­: To retrospectively explore the significance of copy number losses at the 14q11.2 T-cell receptor α locus in relation to the presence of a T-cell neoplasm and proportion of T cells by targeted next-generation sequencing. DESIGN.­: Targeted next-generation sequencing data from 139 tissue biopsies, including T-cell lymphomas, B-cell lymphomas, classic Hodgkin lymphomas, nonhematopoietic malignancies, and normal samples, were reviewed for copy number losses involving the T-cell receptor α gene segments at chr14q11.2. RESULTS.­: We found that biallelic or homozygous deletion of 14q11.2 was found in most (28 of 33, 84.8%) T-cell lymphomas. The magnitude of 14q11.2 loss showed a statistically significant correlation with the proportion of T cells in lymphoma tissue samples. Copy number losses could also be detected in other lymphomas with high numbers of T cells (8 of 32, 25% of B-cell lymphomas, 4 of 4 classical Hodgkin lymphomas), though biallelic/homozygous deletion of 14q11.2 was not significantly observed outside of T-cell lymphomas. Most nonhematopoietic neoplasms and normal tissues (59 of 64, 92.2%) showed no significant copy number losses involving the T-cell receptor α locus at chr14q11.2. CONCLUSIONS.­: Analysis of copy number losses at the T-cell receptor α locus chr14q11.2 with targeted next-generation sequencing can potentially be used to estimate the proportion of T cells and detect T-cell neoplasms.

Reproducibility of endometrial intraepithelial neoplasia diagnosis is good, but influenced by the diagnostic style of pathologists.

Endometrial intraepithelial neoplasia (EIN) applies specific diagnostic criteria to designate a monoclonal endometrial preinvasive glandular proliferation known from previous studies to confer a 45-fold increased risk for endometrial cancer. In this international study we estimate accuracy and precision of EIN diagnosis among 20 reviewing pathologists in different practice environments, and with differing levels of experience and training. Sixty-two endometrial biopsies diagnosed as benign, EIN, or adenocarcinoma by consensus of two expert subspecialty pathologists were used as a reference comparison to assess diagnostic accuracy of 20 reviewing pathologists. Interobserver reproducibility among the 20 reviewers provided a measure of diagnostic precision. Before evaluating cases, observers were self-trained by reviewing published textbook and/or online EIN diagnostic guidelines. Demographics of the reviewing pathologists, and their impressions regarding implementation of EIN terminology were recorded. Seventy-nine percent of the 20 reviewing pathologists' diagnoses were exactly concordant with the expert consensus (accuracy). The interobserver weighted κ values of 3-class EIN scheme (benign, EIN, carcinoma) diagnoses between expert consensus and each of reviewing pathologists averaged 0.72 (reproducibility, or precision). Reviewing pathologists demonstrated one of three diagnostic styles, which varied in the repertoire of diagnoses commonly used, and their nonrandom response to potentially confounding diagnostic features such as endometrial polyp, altered differentiation, background hormonal effects, and technically poor preparations. EIN diagnostic strategies can be learned and implemented from standard teaching materials with a high degree of reproducibility, but is impacted by the personal diagnostic style of each pathologist in responding to potential diagnostic confounders.

STK4 deficiency and EBV-associated lymphoproliferative disorders, emphasis on histomorphology, and review of literature.

Aberrations of the STK4 gene in humans result in an autosomal recessively inherited primary immunodeficiency. We identified three patients with STK4 deficiency who had presented to our hospital and reviewed their biopsy samples with the goal of detailing the characteristics of STK4 deficiency from a pathology perspective. Case 1 was a 20-year-old male who presented with cervical and supraclavicular lymphadenopathy which showed plasmacytic hyperplasia and a concurrent bronchial mass, with AA amyloidosis and EBV-associated "polymorphic lymphoproliferative disorder (LPD) resembling polymorphic post-transplant LPD." The second case was an 8-year-old girl with abdominal lymphadenopathy; biopsy revealed a complex lymphoproliferation which consisted of EBV-associated "polymorphic LPD resembling polymorphic post-transplant LPD," plasmacytic hyperplasia, granulomatous reaction, and a CD4- and PD-1-positive clonal T cell proliferation. The third was a 15-year-old girl with a laryngeal mass, representing a high-grade B cell lymphoma with prominent plasmacytic differentiation. Our cases emphasize the complex and challenging histopathology of lymphoid proliferations in patients with STK4 deficiency.