Just a bread and butter case: with better control of HIV disease it is easy to forget about Kaposi sarcoma - this example with hyaline globules. (erythrophagolysosomes).

This is a subcutaneous pleomorphic liposarcoma. It looks like a "generic" high-grade pleomorphic sarcoma until the pleomorphic lipoblasts are spotted. They may be in a spectrum with the more recently described myxoid pleomorphic liposarcoma. pubmed.ncbi.nlm.nih.gov/3416…

It's a vintage article from Modern Pathology, but keratin expression in schwannomas is an "always" pitfall! IYKYK! pubmed.ncbi.nlm.nih.gov/1635…

Langerhans cell histiocytosis (LCH) can present as colorectal polyps in adults and is generally indolent - analogous to to eosinophilic granuloma. Pediatric gastrointestinal LCH, in contrast, is often devastating. pubmed.ncbi.nlm.nih.gov/3889…

Once in a while, squamous carcinomas are associated with low-risk human papillomavirus (HPV). Vulvovaginal examples seem to have their own special molecular signature; this well-differentiated example arose in the anal canal - fewer data are available. pubmed.ncbi.nlm.nih.gov/4107…

The names have changed for this goblet cell adenocarcinoma, but not the molecular findings. In the past this lesion was a "goblet cell carcinoid" and high grade examples were "adenocarcinoma ex goblet cell carcinoid". Check out this vintage article. pubmed.ncbi.nlm.nih.gov/2942…

Years ago, colleagues noted that paraganglia (NOT paragangliomas) can mimic prostate adenocarcinoma on prostate needle biopsies. In the gallbladder, the issue would be a neuroendocrine tumor! pubmed.ncbi.nlm.nih.gov/1497…

This mammary myofibroblastoma arose in a man's breast (this lesion is more common in men than women). It co-expressed desmin and CD34; Rb protein loss would be anticipated! Good bread and butter!

Checkpoint inhibitor therapy (with nivolumab in this case)-associated injury sometimes mimics traditional immune disease states. The apoptotic keratinocytes damaged by lymphocytes (arrow; Civatte bodies) and lymphocytosis mimic esophageal lichen planus. pubmed.ncbi.nlm.nih.gov/3967…

Some hepatic adenomas are easy - this one is beta catenin activated and thus should be resected. An endothelial cell (negative internal control, arrow) shows no nuclear staining. Note the unpaired artery. However, Mod Pathol offers some tips! pubmed.ncbi.nlm.nih.gov/3716…

The arrows demonstrate hyaline globules (erythrophagolysosomes), the diagnostic clue for pathologists who can diagnose it perfectly well without immunohistochemistry.

Most evidence to date tells us that Kaposi sarcoma (a gastric example is shown) shows differentiation along lymphatic lines, but the spatial relationship between the lesional cells and the company that they keep proves fascinating. pubmed.ncbi.nlm.nih.gov/4147…

The number of times we have diagnosed a GI tract mast cell disorder (systemic mastocytosis seen here) because we spotted it on H&E - quite a few. The number of times we have diagnosed a mast cell disorder because we were asked to do silly stains? ZERO. pubmed.ncbi.nlm.nih.gov/3685…

A striking peritoneal mesothelioma that resulted in small bowel obstruction. Nuclear grading can offer prognostic information! Read all about it in Modern Pathology: pubmed.ncbi.nlm.nih.gov/3306…

Can't interpret mesenchymal tumors? This is nodular fasciitis, now accessible to those who need a little handholding! There's CISH for USP6 - get yours! pubmed.ncbi.nlm.nih.gov/4250…

Ravindran A et al .The University of Alabama at Birmingham Histiocytosis Working Group. Malignant Histiocytosis Comprises a Phenotypic Spectrum That Parallels the Lineage Differentiation of Monocytes, Macrophages, Dendritic Cells, and Langerhans Cells. Mod Pathol. PMID: 37406859

Interdigitating reticulum cell sarcoma can be considered a malignant variant of Rosai-Dorfman disease! S100 protein was + (not shown). Ravindran A, et al . Mod Pathol. 2023 Oct;36(10):100268. PMID: 37406859.

What an array of cases! Wu S, et al. NTRK Fusion Landscape in 195 Positive Cases of 17 Tumors: A Chinese Multicenter Retrospective Study With Optimized Pan-TRK Immunohistochemistry (IHC) Screening. Mod Pathol. 2026 Apr 29;39(7):101007. Epub ahead of print. PMID: 42066846.

Serotonin-producing pancreatic neuroendocrine tumors often have a peculiar sclerotic appearance. Depoilly T, eet al. Immunophenotypic and molecular characterization of pancreatic neuroendocrine tumors producing serotonin. Mod Pathol. 2022 Nov;35(11):1713-1722. MID: 35739266.

The gang in Miami sees plenty HPV-associated anal glandular lesions - but you might be missing them- check it out! Mirzabeigi Y, et al. Expanding the Spectrum of High-Risk Human Papilloma Virus (HPV)-Associated Glandular Neoplasms of the Anorectum. Mod Pathol. PMID: 42392453.