Clear cell sarcoma (imaged): also called melanoma of soft parts. It has t(12;22)q(13;q12) ATF1-EWS translocation. Often positive for melanoma markers (HMB45, S100).

Chordoma: composed of physaliferous cells (with bubbles and vacuoles), separated by fibrous septa within myxoud stroma. Positive for brachyury, S100, CK, muciramine, EMA, vimentin. Occurs in the midline - base of skull, cervical spine, sacrum.

Ethylene glycol poisoning - polarizable calcium oxalate crystals in the kidneys (imaged)

Cat scratch disease: necrotizing granulomas with palisading histiocytes, necrotic debris, neutrophils. It is caused by Bartonella henselae, carried by house cats with fleas. This bacteria can be seen in lymph nodes and stain with the Warthin-Starry stain.

Polymorphous adenocarcinoma arises in the palate. The atypia is mild. Concentric arrangement around the nerves (pictured) can be present. CK7, p63 and EMA positive.

Hemophagocytic Lymphohistiocytosis: a molecular mutation in PRF1, UNC13D or STX11 is characteristic and supports the diagnosis.

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Alveolar rhabdomyosarcoma (imaged) with t(2;13)(PAX3-FOX01) has a worse prognosis. t (1;13)(PAX7-FOX01) has a better prognosis. N-myc amplifications are also common.

Granular cell tumor: SOX10+, S100+, CD68+, neuron-specific enolase +, calretinin+, inhibin +, nestin +. HMB45 -.

Thecoma: lipid vacuolated spindle cells with hyaline globules. Can produce androgen and estrogen and present with dysfunctional uterine bleeding.

Agressive angiomyxoma: a large invasive pelvic lesion, most frequently found in the vulva, hypocellular, with myxoid stroma and bland stellate and spindle cells. +: desmin, vimentin, ER and PR.

Kimura disease is a rare chronic inflammatory disorder that affects Asians. Major features: thick walled blood vessels with hobnail endothelial cells and abundant eosinophils. Co-existing autoimmune disorders and renal failure is commonly found.

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Aspergillus fumigatus: uniseriate compact phialides mostly on the top of the vesicle and round, smooth conidia.

Triple phosphate crystals (imaged): rectangular in shape and bear resemblance to coffin lids; not clinically significant.

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Bacillus anthracis: large, catalase-positive, nonmotile, gram-positive rod with oval endospores. Colonies are round, have a ground-glass appearance, nonhemolytic. There are comma-shaped projections from the edge (“Medusa head"), lecithinase positive,xylose and mannitol negative.

Fibrous hamartoma of infancy: triphasic organoid growth pattern (bands of mature fibrous tissue, nests of primitive mesenchyme within loose myxoid stroma and interspersed mature fat). Axilla, upper limb and trunk. 2 first years of life.