Sandbox:Preeti

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Preeti Singh, M.B.B.S.[2]

Differentiating [disease name] from other diseases on the basis of [symptom 1], [symptom 2], and [symptom 3]

On the basis [symptom 1], [symptom 2], and [symptom 3], [disease name] must be differentiated from [disease 1], [disease 2], [disease 3], [disease 4], [disease 5], and [disease 6].

Scrotal Swelling	Diseases	Clinical manifestations						Para-clinical findings							Gold standard	Additional findings
Painful		Symptoms			Physical examination
								Lab Findings			Imaging			Histopathology
		Symptom 1	Symptom 2	Symptom 3	Tenderness	Testicular Enlargement	Physical exam 3	Lab 1	Lab 2	Lab 3	Imaging 1	Imaging 2	Imaging 3
	Epididymitis				+
	Orchitis				+
	Testicular Torsion				+
	Trauma				+
	Incarcerated Hernia				-
	Insect Bite				-
	Rash				-
	Torsion of testicular appendix				-
Scrotal Swelling	Diseases	Symptom 1	Symptom 2	Symptom 3	Tenderness	Testicular Enlargemet	Physical exam 3	Lab 1	Lab 2	Lab 3	Imaging 1	Imaging 2	Imaging 3	Histopathology	Gold standard	Additional findings
Painless	Fragile X				-	+
	Testicular Tumors				-	+
	Henoch-Schonlein purpura				-	-
	Hydrocele				-	-
	Varicocele				-	-
	Spermatocele				-	-
	Incarcerated hernia				-	-
	Scrotal edema				-	-

Disease Name	History and Symptoms	Physical Examination	Lab Findings	Imaging Findings	Gross and Histologic Findings	Genetic Studies / Immunohistochemistry
Germ Cell Tumors
Seminoma	Most common 30-50 year-old with painless unilateral testicular mass or mild discomfort	Palpable, nontender unilateral testicular mass Usually homogeneous enlargement	Elevated serum placental ALP (PALP)	Hypoechogenic intratesticular well-defined mass on ultrasound with internal blood flow on Doppler ultrasound Cysts and calcificications are uncommon Hypointense lesion with inhomogeneous enhancement on MRI Homogeneous when small and heterogeneous when large	Grey-white homogeneous mass with a lobular appearance Fried egg appearance on histopathology (large cells and clear cytoplasm) Prominent lymphocytic infiltration and less commonly, granulomatous formation	Stains positively for ALP, c-KIT, CD30, EMA, and glycogen
Embryonal cell carcinoma	Young adults Painful testicular mass Manifests with early mestastasis (bone, lung, CNS)	Often unremarkable (small primary tumor)	Elevated serum hCG Elevated serum AFP, when mixed	Variable echogenicity (usually hypoechoic on ultrasound) No differentiating features on imaging Commonly invade the surrounding structures (tunica albuginea) Irregular calcifications	Pale-grey mass with areas of hemorrhagic and necrosis Often mixed histopathological features (solid, papillary, tubular, pseudoglandular)	Stains positively for CD30 and hCG stain May stain positively for AFP, when mixed
Yolk sac tumor	Most common testicular cancer in children less than 3 years of age Rapidly growing unilateral mass in an infant or a young child	Palpable, nontender unilateral testicular mass Usually heterogeneous enlargement	Elevated serum AFP	Diffuse enlargement of the testis with a heterogeneous appearance on ultrasound Areas of hemorrhage and necrosis on MRI	Yellow, mucinous, non-encapsulated, heterogeneous mass with areas of necrosis and hemorrhage Patterns that resemble embryonal structures (yolk sac, allantois) with reticular, papillary, or elongated forms Schiller-Duval bodies (perivascular structures)	Stains positively for AFP, alpha-1-antitrypsin, PAS diastase
Teratoma	Bimodal distribution of age (infants and middle aged adults) Painless tumor History of congenital disease (Down syndrome, klinefelter, spina bifida)	Palpable, nontender unilateral testicular mass Usually heterogeneous enlargement	Elevated serum hCG Elevated serum AFP	Heterogeneous, cystic appearance with mucinous or sebaceous depositions Variable echogenicity on ultrasound Calcifications usually irregular	Large, heterogeneous appearance with solid, cystic, mucoid, and/or cartilageanous components Presence of at least 2 germ layers	Chromosome 12p mutations Stains positively for cytokeratin. hCG, and AFP
Teratocarcinoma	Middle aged adult with painless testicular mass of mild discomfort May manifest with features of metastasis	Palpable, nontender unilateral testicular mass Usually heterogeneous enlargement	Elevated serum hCG Elevated serum AFP	Variable echogenicity on ultrasound	Features of both teratoma and embryonal carcinoma (more common) or both teratoma and choriocarcinoma (less common) Solid and cystic components with mucoid, cartilagenous, sebaceous gland, myxoid stroma components Additional features of underlying embryonal carcinoma or choriocarcinoma	Stains positively for cytokeratin. hCG, AFP, and CD30
Choriocarcinoma	Adolescent or young adult with extratesticular symptoms Mass is small and locally asymptomatic Manifests with early metastasis and signs of hemorrhage (hemorrhagic stroke, hyperthyroidism, cannon-ball metastasis in lung, liver involvement, neurological deficits)	Often unremarkable (small primary tumor)	Elevated serum hCG	Variable echogenicity No differentiating features on imaging Commonly invade the surrounding structures (tunica albuginea)	Prominent areas of hemorrhage and necrosis Nest and sheet pattern that simultaneously includes both cytotrophoblast and syncytiotrophoblast (rarely pure) Paucity of intermediate trophoblasts (unlike placental site trophoblastic tumor)	Stains positively for hCG
Diffuse embryoma	20-25 yo man with painful testicular mass	Tender testicular mass	Elevated serum hCG Elevated serum AFP	Poorly-defined, heterogeneous hyperechoic mass on ultrasound	Non-encapsulated mass Intermingled (lace-like) embryonal carcinoma and yolk sac components in equal proportions, but no discrete embyoid bodies Scattered trophoblastic components Necklace-like arrangement of cells	Stains positively for cytokeratin, AFP (yolk sac component), and CD30 (embyonal component)
Polyembryoma	20-25 yo man with painful testicular mass	Tender testicular mass	Elevated serum AFP Elevated serum hCG	Poorly-defined, heterogeneous hyperechoic mass on ultrasound	Multiple discrete embyoid bodies (combination of both embryonal carcinoma and yolk sac components)	Stains positively for cytokeratin, AFP (yolk sac component), and CD30 (embyonal component)
Placental site trophoblastic tumor	Infant or young adult Painful small testicular mass	Small nontender or minimally painful testicular mass	Elevated serum hCG	Variable echogenicity No differentiating features on imaging May have vascular flow	Solid yellowish mass that resembles uterine tissue Less prominent foci of hemorrhage and ncerosis Predominance of intermediate trophoblast cells (implantation-site type) that invade surrounding blood vessels Paucity of cytotrophoblast and syncytiotrophoblast cells (unlike choriocarcinoma)	Stains positively for hPL (diffuse), cytokeratin, AFP, and hCG (patchy) Negative p63 staining
Epithelioid trophoblastic tumor	Infant or young adult Painful small testicular mass	Small nontender or minimally painful testicular mass	Elevated serum hCG	Variable echogenicity No differentiating features on imaging May have vascular flow	Solid yellowish mass that resembles uterine tissue Less prominent foci of hemorrhage and ncerosis Predominance of intermediate trophoblast cells (implantation-site type) that invade surrounding blood vessels Paucity of cytotrophoblast and syncytiotrophoblast cells (unlike choriocarcinoma)	Stains positively for p63 (diffuse), p63, cytokeratin, AFP, and hCG (patchy) Negative hPL staining
Mixed germ cell tumor	Typical age at diagnosis and other clinical features based on underlying components	Physical exam findings based on underlying components	Elevated serum hCG, AFP, and/or PALP dependeing on the underlying compoenents	Imaging findings based on underlying components	Histopathological findings based on underlying components Variable proportion of choriocarcinoma, embryonal cell carcinoma, yolk sac tumor, seminoma, and/or teratoma tissue	May stain positively for any of CD30, hCG, AFP, ALP, c-KIT, CD30, EMA, alpha-1-antitrypsin, PAS diastase, and glycogen depending on underlying compoenents
Carcinoid (pure neuroendocrine neoplasm)	Middle-aged and elderly adult Manifests as a minimally painful, rapidly growing mass May manifest as carcinoid syndrome	Tender testicular mass Hydrocele or cryptorchidism	Elevated serum and urine 5-HIAA if carcinoid syndrome present	Unilateral, well-circumscribed mass without vascular invasion Solid and cystic appearance Mixed echogenicity on ultrasound Irregular calcifications	Well-circumscribed, yellowish solid mass Occasional cystic masses Small acini, cord-forming rosettes, prominent cytoplasmic granularity Salt and pepper chromatic pattern Absent features of atypia Neurosecretory granules on electron microscopy	Stains positively for cytokeratin, serotonin, chromogranin, synaptophysin, and CD56
PNET (Ewing's tumor of the testes)	30-50 yo man with rapidly enlarging mass Often metastatic at presentation	Palpable, nontender unilateral testicular mass	Unremarkable	No differentiating features on imaging Vascular flow on Doppler	Greyish necrotic mass of immature neural tissue Sheet-like / rosette distribution of small round blue tumor cells Neurosecretory granules on electron microscopy	Stains positively for synaptophysin, NSE, chromogranin, CD99, GFAP, FLI1 Split of EWS gene on chromosome 22
Sex-cord stromal tumors
Fibroma	Middle-aged adult (range 20-70 years) with slowly-growing, painless testicular mass History of nevoid basal cell carcinoma (Gorlin syndrome)	Palpable, nontender unilateral testicular mass	Unremarkable	Isoechoic mass on ultrasound with prominent acoustic shadowing (fibrous component) May be homogeneous or heterogeneous Margins often blended with the tunica albuginea No vascular flow on Dopper	Well-circumscribed, often non-encapsulated solid pale yellow mass No hemorrhage, no necrosis Pure fibromatous features of collagenized plaques and spindle cells that synthesize collagen. Low cellularity	Mutation in PTCH gene Positive staining for calretinin, inhibin, CD56, CD34, actin, vimectin Usually (but not always) negative staining for S-100, keratin, CD99/MIC-2, and desmin
Granulosa cell tumor	Young or middle-aged adult (adult-type) or infant/child (juvenile-type) patient with slowly-enlarging painless testicular mass May manifest with symptoms of metastasis or hormonal secretion (e.g. gynecomastia in estrogen-secreting tumors)	Palpable, nontender unilateral testicular mass	Unremarkable	Hypoechoic mass with solid and cystic appearance on ultrasound (swiss-cheese appearance)	Well-circumscribed tumor between the seminiferous tubules May be solid, cystic, of lobular Pseudo-capsule No hemorrhage, no necrosis Elongated grooved nuclei (coffee-bean appearance) Call-Exner bodies Variable atypia	Stains positively for calretinin, inhibin, vimentin, actin, and MIC2
Leydig (interstitial) cell tumor	Bimodal age distribution Slowly enlarging painless unilateral mass	Palpable, nontender unilateral testicular mass Signs of excess estradiol (e.g. gynecomastia)	Unremarkable	Well-defined, hypoechoic solid mass on ultrasound May have cystic component Irregular calcifications	Well-circumscribed, unencapsulated solid mass Yellowish-brown tumor May have cystic, hemorrhagic, or necrotic areas Often dffuse growth of large polygonal Leydig cells, but may have unique patterns of growth Vacuolated cells with marked atypia Reinke crystals Psammoma bodies	Mutation in fumarate hydratase Stains positively for inhibin, cytokeratin, calretinin, synaptophysin, vimentin, Melan-A
Sertoli hyperplasia (Sertoli adenoma, Pick's adenoma)	Child or young adult with history of Peutz-Jegher syndrome, androgen insensitivity syndrome, or McCune Albright syndrome Slowly enlarging painless bilateral masses	Palpable, nontender bilateral testicular masses Signs of excess estradiol (e.g. gynecomastia)	Elevated serum estradiol Elevated anti-Mullerian hormone and inhibin B Reduced androgen concentration	Hyperechogenic nodules on ultrasound	Well-demarcated yellowish nodules in the testis Unencapsulated nodules composed of Sertoli cells	Stains positively for anti-Mullerian hormone, inhibin A, CK8, and CK18 Negative staining for AFP, hCG, and p53
Large cell calcifying Sertoli cell tumor	Young patient with history of Carney syndrome, Peutz-Jeghers syndrome, or tuberous sclerosis Slowly enlarging painless unilateral/bilateral mass(es)	Palpable, nontender unilateral or bilateral testicular mass Signs of excess estradiol (e.g. gynecomastia)	Elevated serum estradiol	Diffuse and regular (smooth, rounded, large) calcifications Variable appearance on ultrasound Often multiple hyperechogenic regions with strong shadowing Possible increased blood flow	Multifocal, well-circumscribed yellowish-grey nodules Absent hemorrhage or necrosis Patterrns (sheet or trabeculae) of large cells and formation of solid tubules Psammoma bodies Charcot Bottcher crystals on electron microscopy	Stains positively for inhibin, vimentin, calretinin, S100, and cytokeratin Negative staining for laminin, PALP, AFP, and hCG
Sclerosing Sertoli cell tumor	Variable age at presentation (adolescence to elderly) Slowly enlarging painless unilateral mass	Palpable, nontender unilateral testicular mass	Unremarkable	Well-circumscribed hypoechogenic lesion on ultrasound	Well-circumscribed, yellowish-grey nodule Absent hemorrhage or necrosis Tubuules and cords of Sertoli cells surrounded by hypocellular collagenous strome (sclerosis)	Stains positively for calretinin, inhibin, and vimentin Negative staining for cytokeratin, AFP, and hCG
Sertoli tumor, non-specific	Bimodal age districution: either 40-50 year old man or infants with history of Carney syndrome or Peutz-Jegher syndrome Slowly enlarging testicular mass	Palpable, nontender unilateral testicular mass Signs of excess estradiol (e.g. gynecomastia)	Often unremarkable Elevated serum estradiol may be present, less common	Well-circumscribed mass with variable echogenicity	Well-circumscribed, yellowish-grey nodule Hemorrhage and necrosis may be present, but uncommon Features of fetal, prepubertal, and adult Sertoli cells present simultaneously Charcot Bottcher crystals on electron microscopy	Stains positively for vimentin, cytokeratin, inhibin, S100, chromogranin, synaptophysin, and CD99 Negative staining for hCG, AFP, and PLAP
Sertoli-Leylig cell tumor (SLCT)	Young adult or phenotypic female with history of androgen insensitivity Slowly enlarging painless unilateral mass	Palpable, nontender unilateral testicular mass Signs of excess estradiol (e.g. gynecomastia)	Often unremarkable Elevated serum estradiol may be present, less common Abrnomally elevated testosterone among pts with androgen insensitivity	Well-circumscribed mass with variable echogenicity Solid mass with intratumoral cysts may be present	Heterogeneous, lobulated, encapsulated yellowish solid mass Mass contains combination of Sertoli cells and Leydig cells Poorly differentiated cells (immature tubules of Sertoli cells, large Leydig cells)	Stains positively for inhibin, melanA, and CD99 Negative staining for EMA, PLAP, and S100
Testicular tumor of andrenogenital syndrome (testicular adrenal rest tumor)	Post-pubertal patient with history of congenital adrenal hyperplasia (CAH) Often asymptomatic, detected during screening in patients with CAH	Unremarkable testicular exam Other signs of congenital adrenal hyperplasia	Elevated 11-beta-hydroxylase activity Reduced concentrations of AFP, LDH, and hCG	Uniform hypoechogenicity on ultrasound Usually multifocal and bilateral lesions	Hyperplasia, bilateral lesions in testicular hilum Yellowish nodules Cells resemble adrenocortical cells, no mitoses Normal surrounding tissue Absent Reinke crystals	Stains positively for CD56, synaptophysin, and inhibin Negative staining for androgen receptor protein
Other tumors
Lymphoma	Elderly patient (>60 years) with history of lymphoma (commonly diffuse large B cell lymphoma) Unilateral or bilateral painless testicular mass	Palpable, nontender unilateral or bilateral testicular mass	Depends on lymphoma subtype	Diffuse infiltration Hypoechoic solid masses on ultrasound Hypervascularity on Doppler ultrasound	Whitish-tan colored mass Large, pleomorphic malignant cells Seminiferous tubules may be spared or undergo sclerosis Vascular invasion	Stains positively for CD45 Depends mainly on lymphoma subtype Usually negative staining for PLAP and SALL4
Angiosarcoma	Bimodal age distribution Young man with history of teratoma or elderly man with history of radiation or chronic hydrocele Painless/painful testicular mass	Tender or non-tender testicular mass Low-grade fever Scrotal swelling Flank pain Hydrocele	Often unremarkable	Hypervascularity on Doppler ultrasound	Solid vascular lesion Classical pattern of proliferating anastomosing blood-filled channels 2 patterns: solid (sheet proliferation without lumen) and primitive (small lumina filled withblood)	Stains positively for CD31, CD34, lectin, and factor VIII-related antigen Negative staining for pancytokeratin, PLAP, CD45, CD68, CAM5.2, and AE1/AE3
Chondrosarcoma	Young or middle-aged adult with history of teratoma Painless testicular mass	Palpable, non-tender, heterogeneous mass	Often unremarkable	Lobulated mass	Firm, grey mass with irregular lobulations Cartilaginous (chondroid) matrix surrounded by fibrovascular bands Most have non-cartilagenous components (rarely pure)	Stains positively for S100
Hemangioma	Painless testicular mass among pts of any age	Palpable, non-tender, homogeneous mass	Often unremarkable	Homogeneous hypoechoic mass Hypervascularity on Doppler ultrasound	Well-defined hemorrhagic mass Red blood cells in tubules	Stains positively for CD31, CD34, FLI1, and factor VIII-related antigen Negative staining for pancytokeratin, AE, keratin, PLAP, and EMA
Mesothelioma	Middle aged man with painless testicular mass and history of hydrocele or exposure to asbestos	Palpable, non-tender testicular mass Scrotal swelling	Often unremarkable	Thickening of tunica vaginais Solid paratesticular mass Hydrocele	May be benign or malignant Papillary patterns of uniform epithelioid cells with fibrovacular core Polygonal cells with microvilli on electron microscopy Psammoma bodies	Benign: stains positively for p53 (focal) and CEA Malignant: Stains positively for calretinin, WT1, EMA, thrombomodulin, CK5, CK6, CK7 and negative staining for CEA and CK20
Plasmacytoma	Adult (of any age) with concurrent or history of plasma cell neoplasia (commonly multiple myeloma) Symptoms of multiple myeloma (e.g. fatigue, back pain)	Testicular exam unremarkable	Lab findings of plasmacytosis (e.g. anemia, elevated creatinine, hypercalcemia) No specific lab finding for testicular involvement	Poorly circumscribed hypoechoic lesions on ultrasound Hypervascularity on Doppler ultrasound	Large, tan-yellow mass Areas of hemorrahge Atypical plasma cells Tubule effacement in the center and tubule sparing in the periphery	Positive staining for EMA, CD45, CD79am CD138, kappa or lambda light chains, and other plasma cell markers
AIDS-related testicular cancer	Commonly testicular lymphoma or germ cell tumor Patient with history of AIDS presents with testicular swelling or pain Systemic manifestations of underlying malignancy	Palpable testicular mass that may be tender or non-tender	Depends on underlying malignancy	Depends on underlying malignancy	Depends on underlying malignancy	Depends on underlying malignancy
Non-neoplastic mass
Adrenal cortical rest	Usually asymptomatic (incidental finding) Young man with scrotal swelling and dull pain History of congenital adrenal hyperplasia (hydroxylase deficiency)	Scrotal swelling	May be unremarkable If secretory, elevated concentration of adrenal hormone	Heterogeneous, well-circumscribed hypoechoic mass on ultrasound No or minimal vascularity on Doppler No distinguishing features	Well-circumscribed, small, round, orange-yellow nodule Adrenal cortical tissue with absence of adrenal medullary tissue	Positive staining for markers of cortical adrenal tissue
Chylocele	Scrotal swelling in a man with history of filariasis / elephantiasis	Scrotal swelling Negative trans-illumination test	Unremarkable	Fluid collection surrounding the testes	Milky chylous fluid (not waterry) on aspiration Usually no evidence of microfliariae in chylous fluid Abundant leukocytes	N/A
Cystic dysplasia	Young child with history of renal agenesis / dysplasia May be unilateral or bilateral, painless testicular mass	Palpable, non-tender testicular mass	Unremarkable	Irregular cystic spaces witht varying sizes Absence of solid or vascular components	Varying cystic spaces Formation of incomplete connective tissue septa Cells resembling the normal adult rete testes	N/A
Dermoid cyst	Young or middle aged adult with slowly growing painless mass Ruptured cyst may manifest with scrotal swelling, erythema, and pain	Palpable, nontender unilateral testicular mass Usually heterogeneous enlargement	Unremarkable	Onioin-skin appearance on ultrasound Target-shape lesions with halo of hypoechonicity and central hyperechogenicity on ultrasound No vacular flow on Doppler	Mature epithelial tissue May have hair (similar to teratoma) Keratin filled cyst Epidermal epithelium surrounded by pilosebaceious units Formation of lipogranulomas and microcalcifications Absence of atypia	Absence of any mutation (normal 12p) Stains positively for cytokeratin
Epidermoid cyst (keratocyst)	10-40 yo Painless slowly growing testicular mass Ruptured cyst may manifest with scrotal swelling, erythema, and pain	Palpable, non-tender testicular mass Usually heterogeneous enlargement	Unremarkable	Onioin-skin appearance on ultrasound Target-shape lesions with halo of hypoechonicity and central hyperechogenicity on ultrasound No vacular flow on Doppler	Absence of dermal structures, such as hair, sebaceous glands etc. (found in dermoid cyst) Cyst with white keratin debris Lined by squamous epithelium Laminated keratin Granuloma when cyst ruptures	Absence of any mutation (normal 12p)
Granulomatous orchitis	40-60 yo man with sudden-onset testicular tenderness and mass formation History of infection, sarcoidosis, or testicular trauma	Tender testicular mass Fever	Unremarkable	Solid hypoechoic mass	Solid nodule Lymphocytic infiltration and formation of giant cells and macrophages Not true granuloma	N/A
Hematocele	Scrotal mass in patients with history of testicular trauma, torsion, or increased bleeding tendency	Scrotal swelling Negative trans-illumination test	Unremarkable	Fluid collection surrounding the testes	Bloody fluid on aspiration	N/A
Hydrocele	Scrotal mass in patients with history of testicular trauma or epidymitis	Scrotal swelling Positive trans-illumination test	Unremarkable	Fluid collection surrounding the testes	Clear fluid on aspiration	N/A
Macroorchidism	History of fragile X syndrome, FSH secreting adenoma	Large testicle (the testicle itself is large) Signs of underlying disease	May have elevated hormone concentration (e.g. FSH) if secretory adenoma	Large testicle, but normal architecture	Normal testicular findings	N/A
Malakoplakia	Young man with long-standing symptoms of orchi-epididymitis (pain, scrotal swelling) History of immunosuppression	Palpable, tender testicular mass Scrotal swelling Erythema	Positive culture results for bacterial infection (chronic inflammation)	Hypoechogenic mass on ultrasound Increased vascularity on Doppler	Soft yellow friable plaques (malakos=soft | plakos=plaques) Von Hansemann cells (large cells with abundant eosinophilic cytoplasm) and Michaelis-Gutmann bodies (intracytoplasmic inclusion bodies with owl eyes appearance)	N/A
Testicular vasculitits	Middle aged man with history of polyarteritis nodosa (less commonly granulomatosis with polyangiomatosis, Henoch-Schonlein purpura, or giant cell arteritis) History of HBV or HIV Painful testicular mass with intra-testicular hemorrhage Symptoms of underlying vasculitis	Signs of underlying vasculitis Palpable, tender testicular mass Scrotal swelling if vasculitis includes extratesticular structures	Unremarkable	Heterogeneous, hypoechogenic lesion on ultrasound Inreased intralesional vascularity on Doppler	Soft, dark red lesion with areas of hemorrhage Fibrinoid necrosis Vascular wall fibrosis	N/A
Fibrous proliferation (paratesticular fibrous pseudotumor)	Patients of all ages (peak during young adulthood) Slowly growing painless unilateral scrotal masss History of genitourinary infection or trauma	Palpable, non-tender scrotal mass	Unremarkable	Paratesticular mass between tunica layers Hypoechogenic solid mass on ultrasound No vascularity on Doppler	Whitish mass with multinoduular thickening Collagen-rich fibrous tissue with increased fibroblasts Dystrophic calcifications No hemorrhage or necrosis	Stains positiively for actin and keratin Negative staining for ALK-1, beta-catenin
Polyorchism (supranumerary testes)	Often asymptomatic (incidental finding) Young patient with scrotal pain, swelling, hydrocele, varicocele Patients may present with testicular torsion	Palpable, non-tender scrotal mass Scrotal swelling Testicular torsion manifests with excruciating testicular or pelvic pain, erythema, and swelling	Unremarkable	Isoechogenic scrotal mass	Normal testicular tissue	N/A
Spermatocele	Young or middle aged adult with painless testicular or scrotal mass	Homogeneous palpable non-tender testicular or scrotal mass	Unremarkable	Well-defined, homogeneous,, hypoechoic mass on ultrasound Increased vascular flow on Doppler	Splenic tissue (red with clear boundaries) Occasional calcification, thrombi, or fibrosis	N/A
Splenogodal fusion syndrome (ectopic scrotal spleen)	Child or adolescent with painless, left scrotal mass (not right) and history of perimelia (continuous subtype) or cardiac defect (discontinuous subtype)	Homogeneous palpable non-tender scrotal mass	Unremarkable	Well-defined, homogeneous,, hypoechoic mass on ultrasound Increased vascular flow on Doppler	Splenic tissue (red with clear boundaries) Occasional calcification, thrombi, or fibrosis	N/A
Varicocele	Often asymptomatic Dull or sharp testicular pain that increases with standing or physical activity and improves when lying down History of infertility	Scrotal mass and swelling Often left-sided Dilated, tortuous veins "Bag of worms" sensation upon palpation	Unremarkable	On ultrasound, CT/MRI, and venography, apperance of dilated pampiniform plexus veins with serpentine appearance is diagnostic Flow reversal (reflux) with Valsalva maneuver on Doppler Enhancement following administration of gadolinium on MRI	Testicular atrophy in advanced cases	N/A
Testicular torsion	Excruciating, acute, sharp testicular pain that radiates to the pelvis and abdomen Testicular swelling and pain	Scrotal swelling and tenderness	Unremarkable	Focal/diffuse hypoechogenicity on ultrasound No blood flow on Doppler (vs. increased flow in infections) Scrotal wall thickening	---	N/A
Scrotal
Brucellosis	Patient with history of exposure to cattle/sheep/goat/swine or animal products (milk, meat, cheese) presents with acute scrotal pain and swelling Undulant fever and night sweats (characteristic wet hay odor) Relapses common with similar symptoms	Tender testicular mass Fever Hydrocele	Elevated WBC count Positive serum STA test for brucellosis Elevated Brucella IgM and IgG antibodies Urine PCR positive for Brucella	Focal/diffuse hypoechogenicity on ultrasound Focal/diffusre increased blood flow on Doppler Scrotal wall thickening	Granulomatous inflammation with lymphocytic infiltration	Urethral Gram stain demonstrates Gram-negative diplococci
Brucellosis	Patient with history of exposure to cattle/sheep/goat/swine or animal products (milk, meat, cheese) presents with acute scrotal pain and swelling Undulant fever and night sweats (characteristic wet hay odor) Relapses common with similar symptoms	Tender testicular mass Fever Hydrocele	Elevated WBC count Positive serum STA test for brucellosis Elevated Brucella IgM and IgG antibodies Urine PCR positive for Brucella spp.	Focal/diffuse heterogeneous, hypoechoic intratesticular mass on ultrasound Focal/diffuse increased blood flow on Doppler Scrotal wall thickening	Abscess formation at diagnosis is common Grey-white mass suggestive of testicular atrophy Granulomatous inflammation with lymphocytic infiltration	N/A
Gonorrhea infection	Patient with history of unprotected sexual intercourse presents with unilaterla testicular pain, swelling, and fever May be either acute or chronic	Tender testicular mass Fever Hydrocele	Elevated WBC count Gram-negative diplococci on urethral Gram stain Urine PCR positive for Gonorrhea	Focal/diffuse hypoechogenicity on ultrasound Focal/diffusre increased blood flow on Doppler Scrotal wall thickening	Granulomatous inflammation with lymphocytic infiltration	Urethral Gram stain demonstrates Gram-negative diplococci
Histoplasma infection	Chronic testicular enlargement Patients may have systemic manifestations of histoplasmosis	Tender/non-tender testicular mass	Elevated WBC count and eosinophilia may be present (may be normal in chronic cases)	Focal/diffuse hypoechogenicity on ultrasound Focal/diffusre increased blood flow on Doppler Scrotal wall thickening	Caseating granuloma with giant cells	Yeast observed on silver stain
Mumps	Post-pubertal man with recent manifestations of mumps (e.g. parotiditis, pancreatitis, arthritis, myocarditis, meningoencephalitis) presents with acute, unilateral painful testicular mass	Tender testicular mass Hydrocele Fever Parotiditis Rash	Elevated WBC Elevated paramyxovirus IgM and IgG Urine PCR positive for paramyxovirus	Focal/diffuse hypoechogenicity on ultrasound Focal/diffusre increased blood flow on Doppler Scrotal wall thickening	Non-specific interstitial edema, degenerative changes, vascular dilation Lymphocytic infiltration	N/A
Pyogenic epididymo-orchitis	Patient with history of unprotected sexual intercourse presents with acute scrotal swelling and pain	Tender testicular mass Fever Hydrocele	Elevated WBC Bacterial growth on urethral swab specimin (usually E. coli) Urine PCR positive for offending bacterial agent	Focal/diffuse hypoechogenicity on ultrasound Focal/diffusre increased blood flow on Doppler Scrotal wall thickening	Abscess formation in advanced cases Non-specific interstitial edema, degenerative changes, vascular dilation Lymphocytic infiltration Grey-white mass suggestive of testicular atrophy	N/A
Syphilis	Patient with long history of unprotected sexual intercourse presents with painful testicular swelling (tertiary syphilis) Often manifests as epidimo-orchitis that is resistant to conventional antibiotic therapy May have other systemic symptoms of tertiary syphilis	Irregular tender testicular mass Thickened epididymis Hydrocele	Positive syphilis serology (suggest latent syphilis) VDRL may be either positiive or negative Positive dark field microscopy from lesion content	Heterogeneous hypoechogenicity on ultrasound Solid and cystic appearance with areas of necrosis May have increased blood flow on Doppler	Discrete gummas on gross pathology Microscopic features of gumma (interstitial inflammation, lymphocytic and plasma cell infiltration, obliterative endorteritis (endoarteritis obliterans), perivascular cuffing) Spirochetes may occasionally be observed	May stain positively for silver-based methods (Warthin-Starry stain, Wright stain, Levaditi stain)
Tuberculosis	Patient with history of tuberculosis presents with painless mass or chronically dull testicular discomfort Positive constitutional symptoms (weight loss, malaise) May be isolated or may be associated with other systemic symptoms of tuberculosis (e.g. lymphadenopathy, pulmonary lesions, renal involvement) May have concomitant involvement of other GU organs (e.g. prostate, seminal vesicles)	Irregular testicular mass May be tender or non-tender Thickened scrotal skin Hydrocele	Ejaculum may demonstrate positive acid fast bacilli (AFB) staining	Heterogeneous hypoechogenicity on ultrasound No/minimal blood flow on Doppler Hypointense lesion on T1WI MRI and hyperintense on T2WI MRI	Possible abscess formation Caseating necrosis Epithelioid cells and lymphocytic infiltration with presence of multinucleated giant cells	Positive acid fast bacilli staining