An Organ System-Based Approach to Differential Diagnosis of Amyloid Type in Surgical Pathology

Prostatic amyloidosis: pathological features of an underdiagnosed condition

Amyloidosis is a rare disease that can affect genitourinary organs but the involvement of the prostate has been documented in a limited number of cases. We have reviewed morphologic and immunohistochemical features of prostate biopsies or surgical specimens in which an initial diagnosis of amyloidosis was made. Prostatic amyloidosis was diagnosed in 25 patients, 21 of them were needle biopsies (1.16% of these ones). Amyloid was observed inside vessel walls (25 cases) and the stroma (3). No significant differences in the number of affected biopsy samples between patients with and without cardiac amyloidosis were found. In prostatectomies, amyloid was visualized in all the regions of the prostate, being more abundant in the periphery and the posterolateral tissue. Three patients with abundant amyloid in the prostatectomy did not have cardiac amyloidosis. Immunohistochemically prostatic amyloid was positive for transthyretin and P amyloid (24 cases). A amyloid, kappa, and lambda chains were negative. The genetic analysis revealed transthyretin wild-type amyloidosis. Immunohistochemistry was not conclusive in one case of immunoglobulin light chain amyloidosis. In conclusion, prostate amyloidosis is an infrequent finding characterized by the deposition of amyloid inside small vessel walls, and less often in the stroma. It occurs mainly in the periphery of the gland. Amyloid deposits are often subtle and overlooked but relevant as this may be the first sample in which systemic amyloidosis is diagnosed. Immunohistochemistry can be used to subtype amyloid, although there are limitations when confronted with immunoglobulin light chain amyloidosis. Most cases have corresponded to wild-type transthyretin amyloidosis.

Morphological findings in different subtypes of hepatic amyloid

The classic findings have been well described for light-chain amyloid involving the liver. In addition to light chain, however, many additional proteins are now known to be amyloidogenic and can involve the liver. A total of 58 surgical pathology specimens with amyloid deposits were analyzed for patterns of amyloid deposition, including amyloid from light chain lambda (N = 17), light chain kappa (N = 15), transthyretin (N = 15), serum amyloid A (N = 4), apolipoprotein A1 (N = 4), fibrinogen alpha (N = 2), LECT2 (N = 1). Amyloid deposits predominately targeted the liver vasculature, including the walls of the hepatic arteries, portal veins, and sinusoids. While there was overlap, light chain amyloid predominately involved the sinusoids, while transthyretin amyloid predominately targeted the hepatic arteries, especially the larger ones in the hilum and larger portal tracts. Serum amyloid A formed nodular deposits that started in the portal vasculature but then extended into the portal tract stroma, leading to large, bulbous, portal-based amyloid deposits. Apolipoprotein A amyloid also formed large portal-based nodules. Fibrinogen was mild and subtle on H&E and predominately affected portal veins. Amyloid deposits in hilar nerves were prominent with amyloid light chain, transthyretin, and apolipoprotein A1. In conclusion, the histology of hepatic amyloid is diverse and shows several distinct clusters of findings that can aide in recognition in surgical pathology specimens.

Characterization of Amyloidosis in the Gastrointestinal Tract With an Emphasis on Histologically Distinct Interstitial Patterns of Deposition and Misinterpretations

Amyloidosis can involve the gastrointestinal (GI) tract, and deposition can present with varied histologic patterns that make recognition challenging. This retrospective observational study aimed to characterize the deposition patterns in the GI tract and evaluate key quality metrics, including discrepant cases, to improve recognition and provide insight for accurate diagnosis. Sixty-two patients (195 biopsies) with amyloid involvement of the luminal tract were reviewed. Amyloid subtyping by mass spectrophotometry was available for 59 patients. Immunoglobulin light chain (AL) was the most commonly identified subtype (60%), followed by serum amyloid A (AA; 19%) and transthyretin (ATTR; 16%). 150/195 biopsies (77%) were positive for amyloid deposition, with an average of 2.4 positive biopsies per every 3.1 taken per patient. The sites with the highest yield were duodenum (37/37, 100%) and colon (63/74, 85%). Gastric biopsies were most likely to involve the lamina propria (41/45, 91%, P < 0.001), with the background mucosa showing reactive epithelial changes in almost half of the biopsies (20/45, 44%). Several distinct histologic patterns of interstitial deposition were identified, including muscularis mucosae deposition (n = 40, 27% of positive biopsies), peri-Brunner gland (n = 6, 17% of duodenal biopsies), mass-forming (n = 4, 2.7% of positive biopsies, including 3 suspected cases with localized involvement), collagenous colitis-like (n = 3, 4.8% of positive colonic biopsies), and globular (n = 19, 12.7% of positive biopsies). Congo Red was ordered in 81% of cases in which it was requested clinically, with a positivity rate of 30%. Of the 34 cases in which an amyloid workup was requested (but Congo Red was not performed), 14 were positive on reevaluation. Several missed cases had deposition in multiple biopsies, and almost half were missed by subspecialist GI pathologists. Nine misinterpretations were from the stomach, with seven initially diagnosed as chemical or reactive gastropathy. Additional discrepant cases were identified from the duodenum (n = 2) and colon (n = 3), with the vascular-only deposition pattern (n = 3), muscularis mucosae-only deposition (n = 3), and globular pattern (n = 1) identified. Given the challenges of identifying amyloid on hematoxylin and eosin staining, Congo Red ordering percentage should be 100% in clinically suspicious cases unless deposition is definitively seen on hematoxylin and eosin staining.

Kidney Biopsy Corner: Amyloidosis

Amyloidosis is an infiltrative disease caused by misfolded proteins depositing in tissues. Amyloid infiltrates the kidney in several patterns. There are, as currently described by the International Society of Amyloidosis, 14 types of amyloid that can involve the kidney, and these types may have different locations or clinical settings. Herein we report a case of AA amyloidosis occurring in a 24-year-old male with a history of intravenous drug abuse and provide a comprehensive review of different types of amyloids involving the kidney.

Amyloidoma of the Tongue: Case Report, Surgical Management, and Review of the Literature

PURPOSE

Localized amyloidosis of the tongue is a benign condition in which surgical management may be considered. The aim of the study was to review the current literature and report a case.

MATERIALS AND METHODS

We searched the PubMed database for all relevant articles reporting cases of localized tongue amyloidosis published between 1980 and February 2020. In addition, we updated 1 case diagnosed and treated in our department.

RESULTS

A 49-year-old male patient presented with an asymptomatic tongue nodule of the dorsum mimicking median rhomboid glossitis. The results of an incisional biopsy showed an amyloid on Congo red staining and positive findings for the κ light chain by immunohistochemical analysis. The findings of the systemic workup were negative. Therefore, a diagnosis of localized κ light-chain amyloidosis was made. The patient underwent a resection of the lesion, and no recurrence or progression was observed during a period of 18 months. The literature review showed 12 reports describing 21 patients (11 men, 52.3%) with localized tongue amyloidosis. The most common clinical presentation was nodular with a single lesion of the tongue dorsum (15 patients, 71.4%). All cases showed positive findings on Congo red staining. Immunohistochemical analysis findings were available for only 9 patients (42.8%) and showed light-chain amyloidosis. No case showed any systemic involvement or the development of systemic disease. Surgical excision was performed in 9 cases, with recurrence at the site of operation in 2 cases.

CONCLUSIONS

Localized amyloidosis of the tongue is a rare disease in which surgical excision may be therapeutic when a multidisciplinary evaluation does not show any systemic disease. We recommend an excision when the lesion is persistent or shows an enlargement or when discomfort is reported. In the case of any further local recurrence, resection may be repeated.