#PathSky Laryngeal mass, older adult male. Primitive, highly vascular round cell neoplasm for the most part.

#PathSky 53F with shortness of breath and “ground glass” pulmonary opacity. Not a hard dx, but a spectacular (if very unfortunate) case.

#PathSky Abdominal wall mass, middle aged woman. Women basically only get 3 abdominal wall tumors, so it’s got to be a desmoid, DFSP or endometriosis. Classic desmoid morphology, aberrant nuclear beta-catenin. I can hear the cries of “boring..”

#PathSky Someone shared a chest wall Ewing sarcoma with me today, and I queried them about exactly what they were Askin. I should probably retire today.

#PathSky Middle aged woman, leg mass. It all looks like this. More nuclear palisading/ Verocay bodies than you’ve seen in your entire career. Nerve sheath? S100/Sox10 negative. LMS? Negative for all the muscle markers. Any other ideas?

#PathSky Right femur lesion in an older woman. Diffusely keratin-positive with 3 different antibodies.

#PathSky 45 with a forearm skin tumor. Highly cellular, monomorphic spindle cell tumor with a “packeted” pattern and deep, nodular lymphoid aggregates.

#PathSky Large, left sided abdominal/retroperitoneal mass in an older adult. Spindle cell proliferation with associated inflammation. All the outside IHC were negative. What to do next? MDM2 FISH? NGS? Methylation?

#PathSky 43M, forearm mass. At first glance, it looks like some kind of inflammatory process, maybe a synovitis with plasma cells, fibrosis and foamy macrophages.

#PathSky 55F, large retroperitoneal mass. Outside pathologist quite reasonably thought of WDL, but MDM2 FISH was negative. Any other ideas?

#PathSky Large, myxoid paraspinal mass, 79M. Transferred from HemePath to BST as “myxoid sarcoma”. MDM2 was negative.

#PathSky Middle-aged woman with a long-standing neck mass.

www.sciencedirect.com/science/arti... This article discusses the very rare intraosseous RMS harboring FET::TFCP2 or MEIS1::NCOA2 fusions. Was a pleasuring writing this with @folpe-mn-st.bsky.social

#PathSky Abdominal wall mall mass, 65M. Multinodular with thick fibrous septa. Bland spindled to ovoid cells surrounding prominent vessels. Microcystic, pseudoglandular spaces.

#PathSky 37M with a colonic mass. PMH significant only for a thin melanoma of the arm. Long sweeping fascicles of myofibroblasts, thin-walled vessels, perivascular edema, nuclear beta-catenin. “Desmoid- next case.” So why share it here?

#PathSky 64M, upper chest wall skin lesion. There was some discussion of whether this strikingly “packeted”, strongly S100 protein-positive lesion might be a traumatic neuroma.

#PathSky 84M with lung nodule, signed out as “adenocarcinoma, favor pulmonary origin”. There is supposed to be a bit of TTF1 expression, but it is subtle to say the least.

#PathSky 12F with an intra-articular middle finger mass.

#PathSky Judging from PubMed, it seems that the ratio of reported NFATC2-rearranged sarcomas to review articles about NFATC2-rearranged sarcomas is just about 1:1.

#PathSky I’ve been bad about posting, my apologies. Ok, 86M with destructive T12 lesion. Sent in to subclassify the malignant spindle cell lesion. Keratins, melanocytic markers, muscle markers, SATB2 negative.

#PathSky Large retroperitoneal mass in a 44M. Some of it looks like this.

#PathSky I usually like to show cases where the morphology makes sense of the molecular, but here’s one where you kind of need the molecular. Axillary mass, 9 month male. Very hyalinized, infiltration of fat, cracking artifact. Strongly CD34-pos. Giant cell fibroblastoma?

#PathSky 30F with shoulder mass. Nice example of low-grade fibromyxoid sarcoma, with heavily collagenized areas and a very abrupt transition to more cellular nodules with a whorling pattern and a well-developed vasculature. MUC4 IHC is confirmatory. This case has another helpful H+E feature (below)

#PathSky Fatty-appearing thigh mass in a 69M. A solid nodule was present, concerning for dedifferentiation. The solid nodule is lateral in the mass.

#PathSky Perianal mass, 38F. Well-circumscribed, modulated, myxoid. Diffusely S100-positive. Nerve sheath myxoma? Not quite right.

#PathSky Intravascular papillae are fun to photograph. We tend to associate them with Dabska tumor (papillary intralymphatic angioendothelioma), but you can see them in other hemangioendotheliomas, angiosarcomas and non-neoplastic lesions.

#PathSky 43F with a solitary lung mass. Relatively circumscribed, nests and interesting micropapillae of lightly eosinophilic epithelioid cells. Negative for everything except TFE3. Dx?

#PathSky 79M with a superficial neck mass. Wildly pleomorphic, quite cellular- undifferentiated pleomorphic sarcoma, right? There are basically no mitoses though, the cells have abundant granular-glassy cytoplasm, there is a lot of inflammation, and many bizarre cells have nuclear inclusions.

#PathSky Slowly growing superficial leg mass, 38M. Well-circumscribed, phleboliths, thrombosed vessels, cellular spindle cell areas, cavernous vascular channels. Dx?

#PathSky It seems rather appropriate, in this NGS era, that I should have been given a CREM1 chocolate.

#PathSky 43M with a giant, pendulous mass of the inner thigh. The outside clinician and pathologist were concerned for WDL, but their MDM2 FISH was negative. Certainly there is nature fat with fibrous septae and an increased number of somewhat atypical stromal cells? False negative FISH?

#PathSky 5F with a small bowel mass. Ideas?

#PathSky 76M with a testicular mass. The outside was quite convinced this was a germ cell tumor with ITGCN, but it was resolutely negative for germ cell markers, and a broad panel of other markers. What to do next? NGS? Methylation? NGS + methylation?

#PathSky Older adult with a large, prolapsing esophageal mass. An excellent example of a “giant fibrovascular polyp” of the esophagus. Except that essentially 100% of these turn out to be well-differentiated ( or less often dedifferentiated) liposarcomas. pubmed.ncbi.nlm.nih.gov/28984298/

#PathSky Infant with leg mass. Looks like a circumscribed deep mass, but there is subtle involvement of the superficial subcutaneous fat. Small, infiltrating fascicles of rather bland spindled cells. The nodule itself is more cellular, fascicular to storiform, but still bland.

#PathSky 22M, referred here for a “high-grade sarcoma” of the leg. Everyone agree? Wide excision plus chemo plus RT?

#PathSky Recently pregnant 30F. Scattered small “green” nodules noted on C-section. This is a two-for-one. The nodules are an excellent example of so-called granular cell reaction, an unusual histiocytic pseudotumor to blood breakdown products. See page 415 of the most recent Enzinger/Weiss.

#PathSky The vet path people here will be pleased to know that I signed out an “equine hidradenoma” this morning. Ah, the joys of speech to text.

#PathSky 37M with a large retroperitoneal mass. Big, fatty thing. The outside quite rightly worried about well-differentiated LPS and a lipomatous angiomyolipoma, but MDM2, SMA and melanocytic markers were negative. Some WDL are MDM2-neg/MDM4-pos. Should we do more molecular ? Or something else?

#PathSky Have you ever wondered what your radiologists really think about your ability to read films? Mine thought it best to label the tumor with arrows and stars.

#PathSky 32M with extra-axial, dural-based, frontoparietal mass. Clearly malignant epithelioid cells arranged in cords and nests in a sclerotic background. Looks a lot like a sclerosing epithelioid fibrosarcoma, and it is strongly MUC4-positive. So, we’re done, right?

#PathSky Having returned from vacation…Back mass, 17 month M. Looks like a smooth muscle tumor, but infants don’t really get true smooth muscle tumors. And some parts look a bit more primitive. Leiomyosarcoma? Something else?

#PathSky 67F, s/p lumpectomy and RT 5 yrs ago for DCIS, now with a mass IN the breast. The outside was worried about post RT angiosarcoma, in part because of the CD31 and C-MYC. This is just fat necrosis with CD31-pos macrophages. 1- post RTAS occurs in the SKIN, not breast. 2- macs express CD31.

#PathSky It’s interesting how we discover things sometimes. On this particular Sunday, I got an email from an Ortho Onc asking what a JXG was. “Just a benign skin tumor.” “Well, this is deep and eroding bone.” “Erm, let me look at it…” Mostly looks like JXG, but what are those eosinophilic cells?

#PathSky Dear Pathologists everywhere: Please, please, please. Do not entirely submit an 11cm skin excision entirely, in 164 blocks. Yours, Whoever it is You Send Your Consults to.

#PathSky 67M, long smoking hx, LN met. Keratin negative outside- “?sarcoma?” The hx suggests an undifferentiated pulmonary carcinoma with SMARCA4 loss. Our keratin was a bit positive and SMARCA4 is gone. These were originally thought to be thoracic sarcomas but have smoking related mutations.

#PathSky This one definitely needs more than 4 images, so go to the Comments too. 65F, iliac crest lesion. The original pathologists quite reasonably considered an epithelioid hemangioendothelioma, although it was CAMTA1-negative.

#PathSky Since I was on vacation, here’s one more. 47M, arm mass. Don’t overthink it- it’s just an undifferentiated pleomorphic sarcoma. But- the outside was concerned for LMS, because of the diffusely positive caldesmon. Oddly, all the other muscle markers were negative. Can you explain this?

#PathSky 15F, thumb mass. There are no relevant positive immunostains. However, FISH for DDIT3 amplification (not rearrangement) is positive. This is an excellent example of a GLI1-amplified sarcoma. This is a great paper from the MSKCC group. pubmed.ncbi.nlm.nih.gov/38934567/

#PathSky 30M, s/p MVA, eventually required foot amputation. Sxns from the amp were sent elsewhere, where the dx of “histiocytic sarcoma” was made. Agree?