Eosinophilic myocarditis is a rare and frequently fatal disease that is often undiagnosed until autopsy. We report a case of eosinophilic myocarditis with an unusual initial presentation of palpitations that subsequently evolved into ventricular tachycardia storm and death within 4 days. ( Level of Difficulty: Beginner. )

Introduction/Objective The most common non-hematopoietic primary lesions of the spleen are benign and vascular in nature. Most are encountered incidentally at autopsy, trauma, or by imaging. The histologic differential diagnosis is challenging and often requires the use of immunohistochemical stains to distinguish from other aggressive lesions. We present a case of multiple splenic hamartomas discovered incidentally in a routine surgical specimen. Methods A 46-year-old male trauma patient with no known medical history underwent splenectomy after sustaining a grade 3 splenic laceration. Results The specimen weighed 198 grams and featured hemorrhagic capsular disruption. Within the intact parenchyma were multiple non-encapsulated, discrete pale foci ranging in size from 1–9 mm. Microscopically, these corresponded to multiple well-demarcated nodules with tortuous slit-like and dilated vascular channels lined by plump endothelial cells with no significant atypia or mitotic activity, and CD8+/CD31+/CD68+ (focal)/CD21-/CD34- phenotype by immunohistochemical staining. The intervening stroma was disorganized, with abundant foamy histiocytes and scattered lymphocytes with no defined white pulp-like structures. Histopathologic and immunohistochemical findings supported a diagnosis of splenic hamartomas. Conclusion Exclusive to the spleen, splenic hamartomas are composed of mixed normal red and white pulp elements in disorganized configuration. They have no known demographic predilection and are exceedingly rare, with one institutional study reporting an incidence of 0.024–0.13% at autopsies. Congenital malformations of red pulp, neoplasms of red pulp, and post-traumatic reactive origin have been discussed as possible etiologies. Although rarely presenting with splenomegaly and hypersplenism, most cases are asymptomatic. Differentiation from other splenic vascular lesions is often challenging, and CD8 positivity in endothelial cells is usually a defining characteristic. Familiarity with the features of this rare and benign entity is important to distinguish it from malignant primary and metastatic tumors.

Introduction/Objective CDX2 encodes a transcription factor expressed in the nuclei of intestinal epithelial cells. The CDX2 immunohistochemical stain has excellent diagnostic utility in the setting of carcinoma of unknown primary, especially in combination with cytokeratins 7 and 20. While the stain is fairly specific for intestinal origin, it is also expressed in tumors of other origins. Only rare case reports have described positivity for CDX2 in metastatic prostatic adenocarcinoma. Having experienced a diagnostic dilemma involving CDX2 positivity in metastatic prostate cancer, we decided to study the rate of positivity for CDX2 in primary and metastatic prostate carcinomas. A literature search revealed several immunoassay studies and case reports of CDX2 positivity in the primary and metastatic setting. Methods Following IRB approval, a search of the electronic medical records was performed to identify prostatic adenocarcinoma diagnoses on prostatectomy and metastatic specimens. Formalin-fixed, paraffin embedded blocks were obtained. Unstained slides were cut at 4µm and the staining protocol for CDX2 from Cell Marque™ was performed. 109 cases were stained, including 88 prostatectomy and 21 metastatic specimens. Results Of the 109 cases, 75 were negative for CDX2, including 19 of the 21 metastatic cases. Of the remaining 34 cases, 10 were strongly positive for CDX2, including two metastatic cases (clavicle and right iliac bone). The remaining 24 were identified as weakly positive (12 cases), focally positive (7 cases), weakly and focally positive (3 cases), or patchy positive (2 cases). Overall, 36.36% of prostatectomy specimens had tumors with some CDX2 positivity, compared to 9.52% of metastatic cases. The patient ages at diagnosis ranged from 44 to 84 years, with a median value of 59 years, and at metastasis ranged from 51 to 87 years, with a median age of 64. PSA ranged from 2.8 to 3564 at diagnosis (median 9) and undetectable to 2024 at metastasis (median 56). Conclusion CDX2 is often positive to some degree in both benign and malignant prostates, and can present a diagnostic pitfall in the case of metastasis. Hence, CDX2 positivity does not exclude the diagnosis of prostate cancer in the evaluation of unknown primary. In our study, the number of metastatic cases studied was relatively low. Future studies with more cases could better quantify the positive rate for CDX2 in metastatic prostate adenocarcinoma.

Introduction/Objective Extrarenal rhabdoid tumor is a high-grade soft-tissue predominately pediatric malignancy with a frequency of 0.15 per million children less than 15 years. It is associated with del(22) (q11.2) with SMARCB1 loss, recognized by loss of INI-1 staining. It has distinct perinuclear hyaline inclusions; however, this feature can be present in other tumors. We describe a malignant extrarenal rhabdoid tumor involving the heart and great vessels to highlight the multiple modalities required for the diagnosis of this tumor in this unusual location. Methods We utilized routine histology, immunohistochemistry, and electron microscopy. Results This 5 -month -old male presented with respiratory distress due to a mass that invaded the heart, surrounding the great vessels. The tumor was composed of sheets of polygonal large cells with light pink to clear cytoplasm, eccentric nuclei with mild anisonucleosis, peripherally marginating chromatin, prominent nucleoli, with 2 mitoses per 10 high power field. Hyaline perinuclear inclusions were inapparent. There were frequent clusters of lymphocytes and eosinophils, with 10 percent necrosis and moderately increased vascularity. The tumor was positive for vimentin, SMA, EMA, MSA, S-100, keratin, and WT1, and negative for INI-1, CD34, ALK, AFP, PLAP, CD30, myogenin, NeuN1, synaptophysin, chromogranin, and NSE. Electron microscopy demonstrated occasional cells with perinuclear collections of intermediate filaments, some with whorls. The strong positivity for vimentin, keratin, SMA, MSA, S-100, negative staining for INA-1 and CD34, and visualization of perinuclear intermediate filament whorls by electron microscopy helped make the diagnosis of extrarenal rhabdoid tumor. Conclusion Malignant extrarenal rhabdomyosarcomas may occur in the middle mediastinum, invade the heart, occur in the first 6 months of life, and not have the typical rhabdoid cells. Diagnoses depend on multiple modalities

Introduction/Objective Acute interstitial pneumonia (AIP) is a rare disease clinically characterized by rapidly progressing respiratory failure in individuals with no history of respiratory illness or other inciting factors. While most often diagnosed in middle-aged adults, it may present in any age group. Initial presentation is described as influenza- like, and respiratory failure requiring ventilatory support often progresses within weeks to months. Prognosis is poor, with an estimated mortality rate approaching 80% without treatment. Methods We present the case of a 44-year-old male nonsmoker with no significant medical history, who presented in 2018 with 1.5 months of dyspnea and headache initially diagnosed as atypical pneumonia. Chest imaging revealed bilateral opacities; however, microbial workup revealed no evidence of infectious etiology. Autoimmune serology studies were likewise unrevealing. Despite aggressive supportive and medical management, he deteriorated to respiratory failure and succumbed. Results At autopsy, the lungs were symmetrically congested and edematous (combined weight 2,340 g) but free of evident consolidation or discrete lesions. Microscopic examination revealed diffuse alveolar damage with extensive hyaline membrane formation, interstitial edema, and fibroblastic proliferation. The vasculature was severely congested, and the alveoli contained hemorrhage and scattered macrophages. No fungal or mycobacterial elements were identified by staining. Based on the histologic features and clinical context, the diagnosis of AIP was made. Conclusion AIP is a rare, aggressive, and diagnostically challenging disease that includes a broad range of both clinical and histologic differentials. Timely recognition and intervention with aggressive respiratory support and high- dose glucocorticoids are the mainstays of clinical management. The diagnostic role of histology is significant, but hinges on early clinical consideration of AIP as disease progression may later preclude the biopsy procedure. We share this case to raise awareness of this rapidly progressive and diagnostically troubling interstitial lung disease while emphasizing the importance of clinicopathologic correlation.