ABSTRACT Cervical thymic cysts are relatively rare benign cystic lesions that tend to be diagnosed clinically as branchial cysts, which usually present as painless, enlarging neck masses. They can occur anywhere along the normal path of descent of thymic primordia from the angle of the mandible to the sternal notch, with mediastinal extension observed in approximately 50% of cases. They are usually seen in the first decade of life on the left side with a male predominance. Here we report a case of a 15-year-old boy who presented to the hospital with left-sided neck swelling for about 2 months. The neck’s contrast-enhanced computed tomography (CECT) revealed a large, well-defined cystic swelling in the left neck region, showing peripheral enhancement, seen from the submandibular region to the superior mediastinum extending into the retrosternal region. Direct fine needle aspiration (FNA) was done, which showed a benign lesion with inflammatory and cystic characteristics, leading to the possibility of a branchial cyst. The cyst was completely excised surgically. Histopathology showed a thymic cyst with parathyroid tissue. The presence of thymic tissue with Hassall’s corpuscles is essential for the diagnosis. Knowledge of the clinical presentation, cyto-histological findings, and differential diagnosis of cystic cervical lesions in the pediatric population is important to diagnose this rare entity. Hence, though uncommon, when one comes across a cystic cervical region mass in children, a diagnosis of cervical thymic cyst should be kept in mind. Nonetheless, a definitive diagnosis depends on imaging findings as well as intraoperative findings and histopathological examination.

ABSTRACT Villous adenoma is uncommonly seen in the urogenital tract and is even more rarely seen in the upper urinary tract and renal pelvis. Like colorectal adenomas, these neoplasms can transform into adenocarcinoma. The preoperative diagnosis is challenging due to their frequent association with hydronephrosis. Herein, we present the case of a villous adenoma of the renal pelvis in a 62-year-old man presenting with recurrent urinary tract infection. The computed tomography scan showed marked hydronephrosis but no suspicious mass in the right kidney. A laparoscopic right nephrectomy was performed. Gross examination revealed a dilated renal pelvis with an irregular exophytic lesion in the renal pelvis’s upper surface. The histopathological examination showed slender, elongated villi with thin fibrovascular cores, consistent with villous adenoma morphology. Isolated villous adenomas have a favorable prognosis. However, the pathologist should undertake a search for an invasive component.

ABSTRACT Metaplastic breast carcinoma is a rare subtype of invasive breast carcinoma. Metaplastic carcinoma with osseous differentiation is exceptionally uncommon. Because of the heterogenous microscopy of the lesion, various clinical and radiological features are observed, leading to diagnostic difficulty. Herein, we present a case of a 43-year-old female with a recurrent breast lump, who was clinically diagnosed as a phyllodes tumor. However, histopathological examination revealed metaplastic carcinoma with extensive osseous differentiation.

ABSTRACT Primary paraganglioma and small cell neuroendocrine carcinoma of the urinary bladder are rare tumors, comprising 0.05% of all bladder tumors and <1% of all malignant bladder tumors, respectively. These tumors can be the cause of a diagnostic dilemma or misdiagnosis on morphology. Paraganglioma is often mistaken for urothelial carcinoma and small cell carcinoma for poorly differentiated carcinoma or lymphoma. Herein, we report a case of primary paraganglioma and another of a small cell carcinoma of the urinary bladder and discuss their closest differential diagnoses. The diagnostic pitfalls should be kept in mind so that correct, timely diagnosis of these entities can be made due to implications in the management and prognosis.

ABSTRACT Angiomyolipoma with epithelial cysts (AMLEC) is a recently described entity and is an uncommon subtype of kidney angiomyolipomas. AMLEC is a benign entity but usually masquerades a renal cell carcinoma on imaging examination. AMLEC has a distinct histological and immunohistochemical staining pattern, which helps in the pathological diagnosis. We present a rare case of AMLEC in a 26-year-old female, which was provisionally diagnosed as renal cell carcinoma on radiology. We also summarize the differential diagnosis of this rare variant, its characteristic features, and a review of the literature.

ABSTRACT Epithelioid angiomyolipoma is an uncommon subtype of renal angiomyolipoma associated with potentially malignant behavior and is considered a distinct entity by the World Health Organization classification of renal tumors. We present a case of an epithelioid variant of angiomyolipoma with extension into the renal vein, inferior vena cava reaching up to the right atrium. Pre-operatively, a diagnosis of renal cell carcinoma was considered based on imaging findings. Intra-operatively due to extensive adhesions, surgical resection was not performed and only tissue sampling was performed for histopathology. Microscopic examination revealed short fascicles of spindle cells and perivascular epithelioid cells. A differential diagnosis of renal cell carcinoma with sarcomatoid differentiation was considered. The immunohistochemical profile showed tumor cells that express Melan-A and smooth muscle actin, while they were negative for pan-cytokeratin, PAX8, CK7, CD117 and CD34. Therefore a diagnosis of epithelioid angiomyolipoma was rendered. The presence of intravascular thrombi on radiological investigation and carcinoma-like growth pattern on light microscopy may compound an erroneous diagnosis of renal cell carcinoma. Hence, it is prudent for the urologist to consider differential diagnosis other than renal cell carcinoma when confronted with a renal neoplasm presenting with intravascular thrombi. In these cases, a core biopsy should be planned pre-operatively and diagnosis should be made with aid of appropriate immunohistochemical markers.