Histopathology - Subcutaneous Tissue/Skin

Question 1

Answer 1

Actinomycosis (acute inflammation)

 Caused by actinomyces bacteria, which is present in many places, especially endometrium and subcutaneous tissue.

o Gram positive rod part of normal oral flora

o Sulfur granules

 Whole slide is bluish, indicating nuclei of the bacteria

 Many PMN, plasma cells, macrophages

 This is purulent stage of acute inflammation

 Not an abscess because the pus is not well-circumscribed

 Bleeding

Question 2

Answer 2

Foreign Body Granuloma

 Non-immunogenic, from suture
o Giant cells and histiocytes are seen around the fibers, lymphocyte count is lower

 White dots seen on high power are the surgical thread fibers

 Look like nodules macroscopically

Question 3

Answer 3

Rheumatic Nodule

 Related to rheumatic arthritis, a systemic autoimmune disease o Extensor surfaces of upper and lower extremities

 Fibrinous necrosis surrounded by epitheloid cells, then fibrous cap, then lymphocytes outermost

o This is the granuloma

Question 4

Answer 4

Carcinoma basocellular

 Carcinomas are cancers with epithelial layers

 Upper center: no epidermis (ulcerated)

o Ulceration because the tumor under epidermis cuts off blood supply to epidermis o “ulcus rodens” = crawling ulcer
o Hemolyzed RBC on surface

 Trabecule-like structures spread deep into surface o Basophilic

o Islands separated by white line (“retraction”) which is an artifact characteristic for this tumor

 Crowded blue appearance due to basal cells making palisading structure. Most of the basal cells are not mature, i.e. do not show squamous differentiation

o However, a squamous pearl is seen here

 Malignant, but does not metastasize

 Characteristic radial orientation of nuclei

 Associated with sun exposure

o Bottom left: solar elastosis

 Follicles seen on the right side

 Krompecher tumor = slow-growing epithelial tumor derived from basal cells

 Tumor spreads in “neostroma”, which is the tumor’s own, more firm stroma.

 Resection margin on lower left is close to tumor.

Question 5

Answer 5

Carcinoma Planocellular (squamous cell carcinoma)

 Right side looks like normal skin

 Left side has invasion of “keratinized pearls” (the islands in the middle with keratinization)

o Differentiation towards center

 Invasive lesions

 Cells resemble squamous cells, but with disturbed keratinization (they are highly differentiated)

Question 6

Answer 6

Hemangioma Capillare Cutis

 Hair follicles, normal epidermis

 Most common blood vessel tumor

 Bluish regions are the stained tumor cells (nuclei are basophilic)

 Invasive growth, note infiltration between the adipocytes.

o However, this is a benign tumor

o Malignant form is angiosarcoma

 Frequently present at birth and disappear spontaneously

Question 7

Answer 7

Kaposi Sarcoma

 Different types of Kaposi sarcoma o Old age – benign

o Immunocompromised patient – malignant, multifocal

 Caused by herpes virus 8 (=Kaposi sarcoma virus)

 Epidermis appears normal

 Dermis has many blood vessels

o They are small vessels with elongated cells o Brown pigment is hemosiderin.

Question 8

Answer 8

Kaposi sarcoma – immunohistochemical reaction

 Cells that stain brown are positive for KSV

Question 9

Answer 9

Diffuse Large B Cell Lymphoma H&E

 Middle of the slide is crowded. Below that, there are apoptotic cells

 Note blast-like cells with vacuoles and nucleoli

Question 10

Answer 10

Diffuse Large B Cell Lymphoma CD20

 CD20 stains B cells

 Membrane-bound positivity for CD20 indicates that these are B cells

 There is good prognosis with rituximab, which is anti-CD20

 Ki67 would show high grade, large proliferation rate

o There is increased mitosis (not decreased apoptosis)

Question 11

Answer 11

Nevus intradermalis cutis

 Ink seen on right; no remnant seen near resection margin

 Hair follicles

 Stratum corneum, granulosum, spinosum, basale, dermis

 Middle of the top of slide has flattened papilla

 Growth is pushing up under surface of dermis, leading to a polypoid structure

 Extra tissue composed of cells with ring of cytoplasm, making islands

o Multinucleated cells with nuclear inclusions

 Basal layer cells have increased pigment

 Towards the bottom, cells are maturing and getting smaller

 These are intradermal nevus cells

 Nevi may produce melanin (not much seen here)

 Benign tumor

 Other forms of nevi:

o Intraepidermal
o Compound nevus = intraepidermal + dermal
o Junctional nevus = tip of papilla. Should be examined for malignancy over age 30.

Question 12

Answer 12

Melanoma malignum cutis

 Normal skin at top right

 Lymphocytic, perivascular infiltration

 Solar elastosis (degeneration of elastic fibers)

 Hyperparakeratosis = nuclei in the stratus corneum; increased keratin formation, preservation

of the nuclei in the superficial cells, and absence of the stratum granulosum

 End of normal skin epithelium has necrotic cells, debris

o Crust on ulcer = exoceration
 Blue bulge on top is large nodule with brown pigment

o Nests of cells with fibrovascular stroma

 Mitotic figures, big nuclei with macronucleoli indicate that these are active o Polymorphic

 These are melanocytes, the malignant counterpart of nevus

 Nodular, melanin-producing

 Melanoma is a ‘great mimic’ clinically

 Types:

o Superficial: horizontal spread
o Lentigo malignum: localized to epithelium, good prognosis
o Acral lentiginous melanomas: found in keratinized places, thus hidden until it has

spread
 Breslow and Clark stages:

o Breslow gives depth in mm
o Clark gives depth by skin layer

 1 = epithelium
 2 = below epithelium
 3 = vasculature
4
 5 = to fatty tissue of dermis

 BRAF V600E mutation associated with melanoma o Develops in intermittently sun-exposed skin o Targeted therapy vemurafinib

Question 13

Answer 13

Lipoma

 Most common mesenchymal tumor

 Benign

 Normal fat tissue

 Can be painful, but does not generally undergo malignant transformation

 Malignant form is liposarcoma

Question 14

Answer 14

Liposarcoma

 From retroperitoneum

 Most common malignant soft tissue tumor

 At higher magnification, you can see adipocytes, but it is more cellular than a lipoma

 Key feature is the presence of lipoblasts = adipocytes with multiple vacuoles causing imprint

on the nucleus

 Mitosis rarely seen

Question 15

Answer 15

Rhabdomyosarcoma

 Children

 Belongs to small, round cell tumors (along with Ewing and Neuroblastoma)

 Common in the urogenital and head & neck regions

 No normal tissue can be seen here

 Pleomorphic cells with mitotic figures suggest malignancy

 Tadpole cells appear asymmetric, with nucleus pushed to one side and large, eosinophilic

cytoplasm

 Usually diagnosed with immunohistochem

Question 16

Answer 16

Synovial sarcoma

 Despite the name, this tumor does not arise from the synovial membrane and is not always a part of joints.

 Most common in middle-aged adults in extremities and neck

 Biphasic appearance:
o Epithelial-looking (not actually epithelium) o Mesenchymal, spindle cells

 Translocation can be detected by FISH
FISH is used for diagnosis of sarcomas and hematological disorders