Dermpath fellow | Developer of pathlibrary.com, ihcexpert.com
Joined October 2022
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4 Apr 2025
Couldn't be more excited to announce the launch of pathlibrary.com, the virtual slide site I wish had existed during my pathology residency. You can:
- Order special stains to work up cases
- See annotated histologic features
- Prepare for exams with board-style questions
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New pathlibrary.com cases dropped: We're past the 1450 cases mark. Try your hand at working up this challenging soft tissue tumor (case #1450).
(Hint: FOSB IHC )
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Acute vacuolar interface change with dyskeratosis: A pattern with a narrow differential:
* Erythema multiforme, TEN/SJS
* Fixed drug eruption (usually has dermal melanin)
* Acute GvHD
* Reactive infectious mucocutaneous eruption (RIME)
WSI & discussion:
pathlibrary.com/slidebox/?ca…
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Chronic colitis with pyloric gland metaplasia (top left) and Paneth cell metaplasia (bottom right - their granules look similar to eosinophil cytoplasm). Paneth cells are normal in the right side of the colon but signify colitis in the left side.
WSI: pathlibrary.com/slidebox/?ca…
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A case of Ewing sarcoma metastatic to the skin with a classic "light cell/dark cell" appearance.
See the labelled whole slide at: pathlibrary.com/slidebox/?ca…
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A case of pityriasis lichenoides showing its classic features: Mounds of parakeratosis, red cell extravasation, lichenoid inflammation, and lymphocytic exocytosis.
Labelled whole slide: pathlibrary.com/slidebox/?ca…
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A bizarre parosteal osteochondromatous proliferation (BPOP) with disorganized cartilage, disorganized bone, and bland fibrous tissue.
BPOP is benign but locally destructive and has a propensity for the small bones of the hands & feet.
Labelled WSI: pathlibrary.com/slidebox/?ca…
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A case of a Wolffian tumor (previously female adnexal tumor of probable Wolffian origin/FATWO).
These lesions typically show a variety of architectural patterns including tubular, cystic, and solid. Tubules filled with eosinophilic material are common.
WSI: pathlibrary.com/slidebox/?ca…
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Atypical endometrial hyperplasia (top) and background benign endometrial glands (bottom). Note the contrast between small, dark benign nuclei and enlarged, pale, vesicular nuclei of atypical hyperplasia.
Labelled whole slide: pathlibrary.com/slidebox/?ca…
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A desmoplastic nodular medulloblastoma showing characteristic paler areas among more densely-packed small round blue cells.
Molecularly, this subtype of medulloblastoma tends to be SHH (sonic hedgehod pathway)-activated.
See the whole slide at:
pathlibrary.com/slidebox/?ca…
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Hyalinizing trabecular tumor is an aptly-named benign thyroid neoplasm. Ki-67 shows an unusual membranous pattern in these lesions.
What other lesion characteristically shows this Ki-67 staining pattern? Answer at: pathlibrary.com/slidebox/?ca…
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Trying to combat the number of bot accounts signing up for PathLibrary...
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A verrucous cyst showing the same papillomatosis, hypergranulosis, and coarse keratohyalin granules of verruca vulgaris.
These lesions may result from low-risk HPV infection of pre-existing epidermoid cysts.
Whole slide:
pathlibrary.com/slidebox/?ca…
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Plexiform fibrohistiocytic tumors are rare soft tissue tumors of intermediate malignant potential.
They have a plexiform (woven) architecture with fascicles of histiocytoid cells in a collagenous stroma.
See the whole slide:
pathlibrary.com/slidebox/?ca…
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A case of calcifying fibrous tumor, an entity characterized by dense, compact collagen and scattered calcification. These lesions may represent burnt-out IgG4-related disease.
Whole slide:
pathlibrary.com/slidebox/?ca…
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A case of hyaline vascular Castleman disease showing atretic (miniaturized) germinal centers with transgressing hyalinzed vessels as well as germinal center "twinning" (two germinal centers surrounded by a single mantle zone).
Labelled WSI: pathlibrary.com/slidebox/?ca…
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A case of acantholytic squamous cell carcinoma in situ.
Acantholysis in squamous cell carcinoma was once thought to confer a worse prognosis, but this is no longer thought to be the case.
Whole slide:
pathlibrary.com/slidebox/?ca…
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A tendinous xanthoma with a lobular architecture.
Different names for xanthomas:
- On the eyelid: Xanthelasma
- Over tendons: Tendinous xanthoma or tuberous xanthoma
- Patches or plaques in skin folds: Plane xanthoma
- Diffusely distributed, sudden onset: Eruptive xanthoma
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Thought this was a misspelling of "pediatric pathology" at first. But it turns out there's a pathology group that only deals with specimens from the foot and lower leg
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New year, new PathLibrary.com cases: We're up to 1400 cases total, with a focus on frozen sections for the new additions.
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Diagnoses for the images:
- Metastatic colonic adenocarcinoma
- Gastrointestinal stromal tumor (GIST)
- Meningioma
- Mucormycosis
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