Theis, Jason D.

Laser capture microdissection and mass spectrometry (LCM/MS) is a technique that involves dissection of glomeruli from paraffin-embedded biopsy tissue, followed by digestion of the dissected glomerular proteins by trypsin, and subsequently mass spectrometry to identify and semiquantitate the glomerular proteins. LCM/MS has played a crucial role in the identification of novel types of amyloidosis, biomarker discovery in fibrillary GN, and more recently discovery of novel target antigens in membranous nephropathy (MN). In addition, LCM/MS has also confirmed the role for complement proteins in glomerular diseases, including C3 glomerulopathy. LCM/MS is now widely used as a clinical test and considered the gold standard for diagnosis and typing amyloidosis. For the remaining glomerular diseases, LCM/MS has remained a research tool. In this review, we discuss the usefulness of LCM/MS in other glomerular diseases, particularly MN, deposition diseases, and diseases of complement pathways, and advocate more routine use of LCM/MS at the present time in at least certain diseases, such as MN, for target antigen detection. We also discuss the limitations of LCM/MS, particularly the difficulties faced from moving from a research-based technique to a clinical test. Nonetheless, the role of LCM/MS in glomerular diseases is expanding. Currently, LCM/MS may be used to identify the etiology in certain glomerular diseases, but in the future, LCM/MS can play a valuable role in determining pathways of complement activation, inflammation, and fibrosis.

Abstract Objectives There is a paucity of data on penile amyloidosis. We aimed to assess the frequency of different amyloid types in surgical specimens from the penis involved by amyloidosis and correlate relevant clinicopathologic parameters with proteomic findings. Methods Since 2008, our reference laboratory has performed liquid chromatography/tandem mass spectrometry (LC-MS/MS) for amyloid typing. The institutional pathology archive and reference laboratory database were queried to retrospectively identify all penile surgical pathology specimens with LC-MS/MS results between January 1, 2008, and November 23, 2022. Archived H&E-stained and Congo red–stained sections were re-reviewed. Results Twelve cases of penile amyloidosis were identified, which represented 0.35% (n = 3,456) of penile surgical specimens. AL-type amyloid was most frequent (n = 7), followed by keratin-type amyloid (n = 3) and ATTR (transthyretin)–type amyloid (n = 2). AL-type amyloid cases often showed diffuse dermal/lamina propria deposition, whereas all keratin-type amyloid cases were localized to the superficial dermis. Two cases with keratin-type amyloid had concomitant cutaneous findings (penile intraepithelial neoplasia and condyloma). Conclusions This series, the largest to date, demonstrates that penile amyloidosis has a heterogeneous proteomic landscape. To the best of our knowledge, this is the first study describing ATTR (transthyretin)–type penile amyloid.

The spleen is a commonly encountered specimen in surgical pathology. However, little is known about the incidence, morphologic pattern, and clinical features of spleens involved by amyloidosis. We retrospectively identified 69 spleen amyloid cases typed using a proteomics-based method between 2008 and 2020. The frequency of amyloid types, clinicopathologic features, and distribution of amyloid deposits were assessed. Four amyloid types were detected: immunoglobulin light chain (AL) (N=30; 43.5%); leukocyte chemotactic factor 2 amyloidosis (ALECT2) (N=30; 43.5%); amyloid A (AA) (N=8; 11.6%); and fibrinogen alpha (AFib) (N=1; 1.4%). The splenic amyloid showed 5 distinct distribution patterns: (1) diffuse pattern, exhibited by most AL cases; (2) red pulp pattern, exhibited by most ALECT2 cases; (3) multinodular pattern, seen in subsets of AA and AL-kappa cases; (4) mass-forming pattern, seen in the AFib case; and (5) vascular only, seen in a subset of AA cases. Atraumatic splenic rupture was the most common reason for splenectomy in AL cases, while most ALECT2 spleens were removed incidentally during an unrelated abdominal surgery. Splenomegaly was significantly more common in AA spleens than in AL or ALECT2 spleens and was often the reason for splenectomy in this group. In conclusion, splenic amyloid may be underrecognized as it is often an incidental finding. Although, as expected, many of the spleens were involved by AL amyloidosis, ALECT2 emerged as another common spleen amyloid type. Although the spleen amyloid types exhibited characteristic distribution patterns, proteomics-based typing is warranted as some morphologic overlap still exists. Awareness of ALECT2 as a major spleen amyloid type is important for appropriate diagnostic workup and patient management.

Abstract Introduction/Objective Amyloidosis encompasses a heterogeneous group of disorders characterized by abnormal deposition of misfolded proteins leading to progressive organ failure. Accurate amyloid typing is essential for proper patient management, as treatment regimens vary dramatically across different types. Bone marrow (BM) biopsy, in conjunction with fat pad aspiration/biopsy, is often the first step in patients with suspected amyloidosis. Although BM involvement by AL amyloid has been previously characterized, little is known about the incidence, morphology and clinical phenotype of non-AL amyloid in BM. Methods/Case Report We retrospectively identified 1469 BM biopsies by querying our reference laboratory database of 19,298 specimens from myriad anatomic sites typed by mass spectrometry-based proteomics (LC-MS/MS). These were reviewed for frequency of amyloid types (N=1469), distribution of amyloid deposits (N=139), and clinical phenotypes (N=345), with particular emphases on cardiac involvement. Results (if a Case Study enter NA) We identified the following amyloid types: AL (N=1172; 79.8%), ATTR (transthyretin) (N=240; 16.3%), AH (immunoglobulin heavy chain) (N=38; 2.6%), AA (serum amyloid A) (N=17; 1.2%), and Aβ2M (β2-microglobulin) (N=2; 0.1%). ATTR deposits showed striking predilection for periosteal soft tissue and/or periosteal vessels, and rarely involved BM stroma and/or interstitial vessels, while AL variably involved these compartments. AA primarily involved interstitial vessels. Both AL and ATTR cases commonly had a monoclonal gammopathy (AL: 92.9%; ATTR: 62.5%) with concomitant cardiac amyloidosis (AL: 91.6%; ATTR: 100%). Compared to AL, ATTR patients had higher stage cardiac amyloidosis and lower overall survival. Conclusion ATTR is common in BM, constituting16.3% of cases in our cohort. Rarer amyloid types, such as AA, AH and AB2M can also occur in BM. ATTR was frequently identified in patients with concomitant monoclonal gammopathy, in whom AL may have been suspected. Although ATTR deposits have distinctive morphologic distribution, primarily involving periosteal soft tissue and/or periosteal vessels and rarely involving BM stroma and/or interstitial vessels, there is considerable morphologic overlap with AL. Therefore, it is imperative to type BM amyloidosis, preferably by LC-MS/MS, to ensure proper patient management. Furthermore, BM involvement by ATTR may be a marker for advanced stage of disease.