Primary localized bladder amyloidosis with negative postoperative Congo red staining: A case report

Abstract

Localized bladder amyloidosis is a rare disorder mimicking bladder tumor, with merely over 200 reported cases. Here, we report a case of a 67-year-old female presented with painless gross hematuria. A positive Congo red staining of the cystoscopy biopsy raised suspicion of bladder amyloidosis, and transurethral resection of the mass was performed. Interestingly, the histopathology of the excised mass showed pink-staining material under Hematoxylin and Eosin staining, but negative Congo red staining. This case demonstrates that a negative Congo red staining doesn’t exclude amyloidosis. An accurate diagnosis should rely on a comprehensive evaluation of clinical, laboratory, radiological, and histopathological findings.

1 Introduction

Localized amyloidosis can manifest in any organ, often without accompanying systematic diseases. The bladder, an uncommon site for this condition, requires clinical attention as it can present symptoms indistinguishable from those of urinary malignancies. Histopathological examination plays a pivotal role in differential diagnosis, with Congo red staining serving as a key diagnostic indicator for amyloid deposits. However, negative Congo red staining doesn’t necessarily rule out amyloidosis. Here, we report a case of localized bladder amyloidosis with a literature review. Notably, this patient was still diagnosed with localized bladder amyloidosis despite the postoperative histopathology showing a negative Congo red staining, highlight that Congo red staining isn’t the exclusive diagnostic standard for amyloidosis.

2 Case presentation

A 67-year-old non-smoker female with a 6-month history of painless gross hematuria was admitted to our hospital. The hematuria was intermittent and red in color with no clotting. Accompanying symptoms included occasional irritative voiding symptoms and lower abdominal pain. She denied fever and joint pain. Physical examination revealed no abnormalities. Computed tomography (CT) showed normal bladder wall thickness with no evidence of masses or lesions ( Fig. 1 ). Upon cystoscopy, a 2 × 2 cm dark-red lesion was identified on the posterior bladder wall. Histopathology examination demonstrated uniformly pink-staining material in the specimen. Further analysis with Congo red staining under polarized light microscopy revealed a characteristic “apple-green” birefringence, which is indicative of amyloidosis. Evaluation concerning systematic amyloidosis all returned negative. The patient denied any history of chronic inflammatory conditions (including rheumatoid arthritis, systemic lupus erythematosus, tuberculosis, etc.) that could lead to secondary amyloidosis. Transurethral resection of the bladder tumor (TURBT) was then performed ( Fig. 2 ), and histologic sections displayed chronic inflammation in the urothelial mucosa and edema in the submucosal layer with pink-staining material deposition and thickening of the vascular walls via Hematoxylin and Eosin (H&E) staining ( Fig. 3 ). However, Congo red staining of the specimen yielded a negative result. Still, considering the patient’s clinical symptoms, the histopathological findings from the preoperative cystoscopy biopsy, and the identification of pink-staining material in the tissue excised through TURBT, a diagnosis of localized bladder amyloidosis was made. The patient’s symptoms quickly relieved after the surgery. A subsequent cystoscopy conducted approximately 3 months following TURBT showed smooth bladder mucosa with no evidence of recurrence ( Fig. 4 ).