Angiomyomatous hamartoma => Usually incidentally enlarged inguinal node in young males ... Typified by the presence of bands of smooth muscle reaching to edge of cortex +/- hilar fat.

Reference: http://iv.iiarjournals.org/content/26/3/459.long

Amyloidosis => Look in nodes from patients with marginal zone lymphoma, lymphoplasmacytic lymphoma or plasma cell neoplasms

Reference: https://www.ncbi.nlm.nih.gov/pubmed/3539760

Bacillary Angiomatosis => Less common in developed countries with wider availability of HAART HIV therapy, but still present in HIV endemic areas.

Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC172893/

Burkitt Lymphoma => 90% will have identifyable MYC rearrangements, but MYC-neg cases occur and show classic histologic features. These may carry 11q aberrations. Immunohistochemistry with Bcl-2 & Tdt neg, MYC protein pos at high levels can help with the differential.

Reference: https://ncbi.nlm.nih.gov/pubmed/24398325

Castleman disease => Hyaline Vascular variant: common, usually localized, may cause unexplained anemia; Plasma cell Variant: can be multifocal, more aggressive, think HIV/HHV8 (or concommitant Kaposi sarcoma)

Reference: https://www.ncbi.nlm.nih.gov/pubmed/19546611

Dermatopathic lymphadenopathy => In Kids -> the differential diagnosis is w/ LCH (which unlike dermatopathic Langerhans cells, will be cyclinD1 neg). In Adults -> Always briefly consider mycosis fungoides or other T-cell lymphoma related dermatopathic change.

Reference: https://ncbi.nlm.nih.gov/pubmed/28622183

Dilantin adenopathy => Changes may simulate cat-scratch, Kikuchi or lymphoma ... But history of seizure disorder and timing with medication is key!

Reference: https://www.ncbi.nlm.nih.gov/pubmed/4137045

EBV lymphadenitis -> EBV ISH will be positive in a spectrum of variably sized B-cells, unlike in EBV-related lymphoma where, typically, all EBV pos B-cells are same size.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/21320728

Fujimoto-Kikuchi lymphadenitis 😉 -> Similar histology with SLE adenitis. A MPO stain is neat way to highlight crescenteric histiocytes in KFH. This can be helpful to distingus proliferative Kikuchi disease from T-cell lymphomas. Beware not to overcall CD8+ T-cells as a T-lymphoproliferative disorder, these immunoblastic T-cell are enriched in KFD.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/11549584

Gaucher's disease -> Classic combination of young age, failure to thrive and organomegaly in liver, spleen and nodes. Rare... but exciting when you catch it.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/18466035

Herpes lymphadenitis -> Typical changes are punctate, neutrophilic abscesses with rare nuclear viral inclusions. Sometimes, isoalted herpes lymphadenitis can be seen as local reactivation in CLL nodes!

Reference: https://www.ncbi.nlm.nih.gov/pubmed/?term=10506706

Immunodeficiency: HIV w/ follicle lysis -> Floird follicular hyperplasia + germ center hemorrhagic lysis. With right history, always 👀 for Kaposi or Toxoplasmosis changes in background.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/3876855

Immunodeficiency: Congenital -> "Empty looking nodes" with few follicles +/- well devloped germinal centers, 🔼plasma cells & 🔽 T-cells. +/- Granulomas. Increased risk of lymphoma of various types.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/?term=28395106

Jirovecii (Pneumocystis) adenitis 😉-> Necrotizing granulomas, "bubbly" histiocytes, few neutrophils. Uniform size of organisms and absence of budding argues against Histoplasmosis

Reference: http://www.archivesofpathology.org/

Kawasaki adenopathy: Rarely nodal disease with fevers is 1st presentation. Mottled node with microangiopathic vascular thrombus + ischemic changes.

Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3637400/pdf/nihms424460.pdf

Kimura disease: Benign inflammatory adenopathy with peripheral eosinophilia. Hyperplastic follicles + prominent vessels + eosinophils & polykaryocytes.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/17425383

Kaposi sarcoma: HIV+ patients with HHV8 coinfection. I was once schooled by a Hungarian colleague that name is pronounced Kap-o-Shee, not kap-Oh-seeeee.

Reference: http://www.archivesofpathology.org/doi/pdf/10.5858/arpa.2011-0213-OA

Leishmaniasis (Visceral): Can rarely find granulomas with intracellular "dots in spaces" pattern. Highlighted best with Giemsa stains on thinly sectioned slides or touch imprints fixed in EtOh.

Reference: http://www.archivesofpathology.org/doi/pdf/10.1043/2010-0069-OA.1

Lepromatous leprosy: Prevalent in developing parts of the world. Highlighted in paraffin tissues or direct smears as weakly acid fast or, better yet, with Fite stain.

Reference: http://cltri.gov.in/TrainingMaterial/4.8-%20Classification%20&%20treatment.pdf

Mastocytosis: Lymph node involvement usually obaserved in systemic forms. Sometimes one can see concurrent marked 🔼 in eos. CD117/CD25+ phenotype, often with KIT-D816V mutation.

Reference: https://academic.oup.com/ajcp/article/132/3/438/1766132

Nodular LP HL: CD20+ B-cell lymphoma with "mass in mass" pattern of nodal effacement and increased numbers of PD-1+ T-fh cells. Differential diagnosis includes: cHL and TCRLBCL Note the numerous variant patterns in this excellent reference 👇🏾!!!

Reference: https://www.ncbi.nlm.nih.gov/pubmed/14508396

Old Man Groin Node: Look, I did my best. Read all my lymph node books. Googled for an hour. This is the best I could come up with. Authoritative reference ?? 👇🏾

Reference: https://www.ncbi.nlm.nih.gov/pubmed/12973685

Progressive transformation of germinal centers -> Disruption of germinal centers by mantle zone lymphocytes. Despite historical suggestions otherwise, this is not precursor lesion to NLPHL. Importantly, it can explain persistent adenopathy.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/26410017

Proteinaceous Lymph node -> Rare⚠. Extracellular nonamyloid Immunoglobulin deposits causing enlargement which can be associated with plasma cell dyscrasia or rheumatic diseases.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/2294866

Quinsy (aka peritonsillar abscess 😏 --> Okay, I cheated a bit for this letter and used a tonsil. Take a peek for HSV on your next quinsy...you might be surprised to encounter innocent herpes infections.

Reference #1: https://www.ncbi.nlm.nih.gov/pubmed/17141448

Reference #2: Check out this nice paper on Herpesvirus tonsilitis by Lester Thompson and colleagues https://www.ncbi.nlm.nih.gov/pubmed/24338612

Rosai-Dorfman disease (of course!) --> Dr. Dorfman once impressed upon me that if one doesn't see lots of plasma cells, don't make this diagnosis. Some extra-nodal forms can be tricky to identify. Recently, some studies show an association with IgG4 excess in a subset of Rosai-Dorfman disease.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/26966089

Bonus content: See this nice obituary of Dr. Dorfman, indeed a giant figure in lymph node pathology

Sarcoidosis -> Tightly formed granulomas, usually without necrosis. Focal punctate necrosis can be seen on occasion. Be careful with GMS though, as pseudo-fungal yeast representing Hamazaki-Wesenberg bodies can be found!👇🏾

Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2014861/

Toxoplasma adenitis -> Lymph node changes in 3 acts: 1) florid hyperplasia, 2) histiocyte clusters push germinal centers, and 3) monocytoid B-cell expansion. Serology + history is far more useful than Toxo IHC

Reference: https://jcp.bmj.com/content/jclinpath/58/11/1143.full.pdf

Vascular transformation of lymph nodes -> Vasoproliferative lesion of lymph nodes that may explain persistent adenopathy and be associated with prior lymph node dissections.

Reference: https://www.ncbi.nlm.nih.gov/pubmed/2069211

Visceral larva migrans -> Toxocara larvae induced eosinophilic macroabscesses +/- Splendore-Hoeppli reaction. Similar changes with any metazoan larvae in nodes.

Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3593479/

Whipple lymphadenopathy -> Characteristic low-power "lymphangiogram" pattern of open cystic spaces + granular histiocytes. Gram+/PasD+ organisms.

Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC88990/

Yersinia lymphadenopathy -> Characteristic epithelioid necrotizing granulomas localized to the germinal centers. Mesentery and bowel lymph nodes are most commonly involved.

Reference: https://www.jstage.jst.go.jp/article/jslrt/52/1/52_1/_pdf/-char/en