🔬 Epithelioid Hemangioma •Benign vascular neoplasm composed of well-formed vessels lined by plump epithelioid endothelial cells. •Typically shows a well-demarcated lobular architecture, with more solid/cellular areas centrally and better-formed vascular lumina peripherally. •Endothelial cells have abundant eosinophilic cytoplasm, vesicular nuclei, and may show nuclear lobulation/clefting and intracytoplasmic vacuoles (blister cells). •Cytological atypia is usually mild and mitoses are infrequent. •A variable lymphocytic/eosinophilic inflammatory infiltrate may be present. •Endothelial markers: ERG, CD31 and FLI1 positive; CD34 is variable. •FOS/FOSB rearrangements are identified in approximately half of cases and can support the diagnosis in challenging cases. •The key is to recognize true vasoformation with epithelioid endothelial lining, rather than diagnosing malignancy based on epithelioid morphology alone. 🌟 Differential diagnosis •Pyogenic granuloma: Characteristic lobular capillary proliferation, often with surface ulceration; lacks the prominent epithelioid endothelial morphology of EH. •Epithelioid haemangioendothelioma: Cords/nests of epithelioid cells in myxohyaline stroma, often with intracytoplasmic vacuoles; vasoformation is much less prominent. •Epithelioid angiosarcoma: Destructive infiltrative growth, marked cytological atypia/pleomorphism, increased mitoses and necrosis, with irregular vascular channels or solid malignant areas. Take-home message: 👉 Epithelioid morphology does not equal malignancy. In EH, the combination of well-formed vasoarchitecture, characteristic epithelioid endothelial cells, low-grade cytology and appropriate endothelial immunophenotype is the key.   💎 Well-formed vessels + plump epithelioid endothelial cells + inflammatory/eosinophilic background + absence of significant malignant atypia   Case courtesy @annsmiley78 #EpithelioidHemangioma #VascularPathology #Dermatopathology #SurgicalPathology #Histopathology #PathologyEducation #ERG #Immunohistochemistry

💡When Keratin Misleads: Keratotic BCC Mimicking PTT! A 51-year-old man with a longstanding sun-exposed scalp lesion developed recent discharge. Histology showed a prominent nodular, basaloid to squamous proliferation with keratin-filled cystic structures, creating a challenging differential: 🔹 Keratotic BCC 🔹 SCC with follicular differentiation 🔹 Proliferating trichilemmal tumour (PTT) – benign/malignant Interestingly, SCC with follicular differentiation received the maximum votes, followed by malignant PTT. Keratotic BCC was not the leading choice — and I had the same dilemma initially! 🧩 The diagnostic clue: IHC BerEP4: diffuse, strong positivity → strongly supports BCC and argues against conventional SCC and PTT. BCL2: diffuse positivity → supportive of BCC. EMA: negative → favours BCC over SCC. CD34: Negative in tumor cells - favors BCC over PTT 🎯 The take-home point Don’t be fooled by the keratin! Keratotic BCC can show prominent squamous/follicular differentiation and closely mimic SCC or PTT. 👉 Look carefully for the underlying BCC architecture and use BerEP4 as a valuable adjunct when morphology is equivocal. Final diagnosis: KERATOTIC BASAL CELL CARCINOMA. Sometimes the most difficult cases are those where the morphology makes you believe the wrong diagnosis first! 😉 #Dermatopathology #KeratoticBCC #BasalCellCarcinoma #ProliferatingTrichilemmalTumor #SCC #Histopathology #Pathtwitter

💡From Fluid to Tissue: Unmasking Lung Adenocarcinoma 🫁 👉 Clinical details: 64 YO man presenting with seizures was found to have a lung mass with mediastinal/hilar and supraclavicular lymphadenopathy, pleural and pericardial effusions, and multiple FDG-avid skeletal lesions. Pericardial fluid was submitted for cytological evaluation. 🔬 Cytology: The pericardial fluid shows numerous malignant epithelial cells arranged predominantly in cohesive three-dimensional clusters, with occasional gland-like architecture. The cells exhibit enlarged hyperchromatic pleomorphic nuclei, irregular nuclear contours, increased N:C ratio and prominent nucleoli — features consistent with metastatic adenocarcinoma. 🫁 Histology: Lung biopsy demonstrates an infiltrative adenocarcinoma with glandular/acinar differentiation, focal lepidic pattern and cytological atypia. Immunoprofile: CK7+, TTF-1+, Napsin A+ CK20−, CDX2−, P40- The morphology and immunophenotype support primary pulmonary adenocarcinoma, with the malignant cells in the pericardial fluid representing metastatic involvement of the pericardium. 🔗 Cyto-histologic correlation: A great example of how cytology can provide a diagnostic clue, while tissue morphology and a focused immunohistochemical panel establish the primary site. Take-home message: 👉 In a malignant serous effusion, morphology gives the diagnosis; a judicious IHC panel helps reveal the origin.   Hashtags #Pathology #Cytopathology #Histopathology #LungCancer #LungAdenocarcinoma #Adenocarcinoma #PericardialEffusion #MalignantEffusion #EffusionCytology #CytoHistologicCorrelation  #PulmonaryPathology #DiagnosticPathology  #PathologyTwitter #MedTwitter

💡When Keratin Misleads: Keratotic BCC Mimicking PTT! A 51-year-old man with a longstanding sun-exposed scalp lesion developed recent discharge. Histology showed a prominent nodular, basaloid to squamous proliferation with keratin-filled cystic structures, creating a challenging differential: 🔹 Keratotic BCC 🔹 SCC with follicular differentiation 🔹 Proliferating trichilemmal tumour (PTT) – benign/malignant Interestingly, SCC with follicular differentiation received the maximum votes, followed by malignant PTT. Keratotic BCC was not the leading choice — and I had the same dilemma initially! 🧩 The diagnostic clue: IHC BerEP4: diffuse, strong positivity → strongly supports BCC and argues against conventional SCC and PTT. BCL2: diffuse positivity → supportive of BCC. EMA: negative → favours BCC over SCC. CD34: Negative in tumor cells - favors BCC over PTT 🎯 The take-home point Don’t be fooled by the keratin! Keratotic BCC can show prominent squamous/follicular differentiation and closely mimic SCC or PTT. 👉 Look carefully for the underlying BCC architecture and use BerEP4 as a valuable adjunct when morphology is equivocal. Final diagnosis: KERATOTIC BASAL CELL CARCINOMA. Sometimes the most difficult cases are those where the morphology makes you believe the wrong diagnosis first! 😉 #Dermatopathology #KeratoticBCC #BasalCellCarcinoma #ProliferatingTrichilemmalTumor #SCC #Histopathology #Pathtwitter

🦠 Herpes Zoster •Patient: 62-year-old male •Clinical presentation: Typically presents with painful, grouped vesicles or pustules on an erythematous base, usually following a unilateral dermatomal distribution. •Etiology: Reactivation of varicella-zoster virus (VZV), which remains latent in sensory dorsal-root or cranial nerve ganglia after primary varicella infection. •Gross: Vesicles may become pustular, hemorrhagic, crusted or eroded/ulcerated as the lesion evolves. 🔬Microscopy: ◦Intraepidermal vesiculation with ballooning degeneration ◦Acantholysis and epidermal necrosis ◦Multinucleated keratinocytes ◦Nuclear molding ◦Margination of chromatin ◦Cowdry type A intranuclear inclusions ◦Underlying mixed dermal inflammatory infiltrate 💎 Key diagnostic clue: The combination of multinucleation + nuclear molding + chromatin margination is characteristic of herpesviral cytopathic change. •Differential diagnosis: HSV infection vs VZV infection. These cannot be reliably distinguished on H&E alone. •Confirmation: VZV and HSV-1/2 immunohistochemistry or PCR can establish the viral type when clinically required. #HerpesZoster #VaricellaZosterVirus #VZV #Herpesvirus #Dermatopathology #Dermpath #Histopathology #Pathology #PathologyCases