Dermal Neoplasms

Question 1

AKA

Histology

Variants

Immunos

Answer 1

Dermatofibroma

AKA fibrous histiocytoma

• Epidermal hyperplasia overlying proliferation of spindled to histiocyteoid cells with multinucleated or Touton giant cells and stromal changes
• entrapped collagen at periphery
• Table-top epi

Variants

1. Histiocytic
2. lipidized
3. hemorrhagic (aneurysmal)
4. hemosiderin deposition (sclerosing hemangioma)
5. granular cell
6. clear cell
7. atypical (or DF with monster cells)
8. cellular

Immunoperoxidase:

Positive for CD163, CD68, Factor XIIIa

Negative for CD34

Question 2

Answer 2

Dermatofibromasarcoma protuberans

Mitoses uncommon

Immunoperoxidase:

CD34+

FXIIIa-

Question 3

Histology

DDX

Immunos

Answer 3

Atypical fibroxanthoma

superficial (dermal) variant of MFH/pleomorphic sarcoma (if there is invasion into subcutis it is MFH)

Solar elastosis, large bizzare tumor cells and mitoses

Immunoperoxidase:

• CD10+
• CD99+
• S-100 -
• CK -
• desmin -
• CD34 -

Question 4

Answer 4

Leiomyoma (pilar type)

small fascicles bland, eosinophilic spindle cells in mid-dermis (resembles arrector pili-smooth muscle of hair erection)

Question 5

Answer 5

Leiomyoma (vascular type)

eosinophilic spindle cells in deep dermis surrounding vessels

Question 6

Leiomyosarcoma immuno

Answer 6

Actin +

Desmin +

S100-

CK-

Question 7

Answer 7

Palisaded encapsulated neuroma

Face often

Well circumscribed but poorly encapsulated

Clefts

Upper dermis

Stroma less myxoid than neurofibroma

Question 8

Answer 8

Granular cell tumor

• Epidermal hyperplasia overlying proliferation
• Histiocytoid cells containing lysosomes and small round nuclei
• Lacks mits/atypia
• Related to schwannoma
• S100 +
• NSE +
• PAS +
• CD68 +
• Inhibin +
• NKI/C3+

Question 9

Answer 9

Lobular capillary hemangioma (pyogenic granuloma)

Mixed inflammation

Often crusted/ulcerated

Question 10

Answer 10

Targetoid hemosiderotic hemangioma

Wedge-shaped, superficial vessels that are dilated

Vessels have hobnail cells

Deeper vessels are slit-like and a/w hemosiderin and hemorrhage

Question 11

Answer 11

Kaposi sarcoma

Slit-like vessels surrounding a central one

PCs

extravasated RBCs

hyaline globules (represent degenerating RBCs)
Promontory sign - tumor cells go into preexisisting blood vessels

HHV8+

Question 12

Clinical

Histology

Answer 12

Mastocytosis

Clinical: urticarial pigmentosa, solitary mastocytoma or bullous lesions; positive Darier’s sign (wheal produced by stroking)

Histo: monotonous infiltrate of oval cells, usually upper dermis, increased eos

Question 13

Answer 13

Juvenile xanthogranuloma

Dermal-based nodular infiltrate of histiocytes and lymphs, multinucleated giant cells (Often Tuton)

Some giant cells contain lipid

Some cases have spindled cells

Older lesions may have fibrosis

Question 14

Clinical

Histology

Immunos

Answer 14

Merkel cell carcinoma

Clinical:

• rapidly growing nodular dermal mass
• Elderly
• sun-damaged skin

Histo:

• Nodular to sheet-like collections of small blue cells with hyperchromatic to vesicular nuclei and scant cytoplasm
• numerous mits and apoptoses
• necrosis
• pagetoid spread

Immunoperoxidase:
Positive for: panCK, CK20 (perinuclear and dot-like), chromo/synapto

negative for CK7 and TTF1