30 Dermatopathology

CD1a Stains Langerhans cells Examples: Langerhans cell histiocytosis

CD43 (Leu-22) Pan-T-cell marker Aberrant coexpression with B-cell marker

CD20 is strongly suggestive of B-cell lymphoma

BCL2 An oncogene that inhibits apoptosis Positive in nodal follicular center cell

lymphomas with chromosomal translocation Rarely positive in cutaneous follicular center

cell lymphomas Most basal cell carcinomas reveal diffuse

BCL2 staining, whereas trichoepitheliomas only show staining of the outermost epithelial layers of the tumor islands

Proliferation markerMIB-1 (Ki-67) More sensitive indicator of cell proliferation

than mitotic figures Helpful in lymphoma and melanoma

Transport media

RoutineFor most purposes 10% buffered formalin is the recommended fixative. The length of time for fixation depends on the specimen size: 12 h/mm thickness is required.

Electron microscopyGlutaraldehyde is the preferred fixative for elec-tron microscopy.

ImmunofluorescenceFor tissue that is not flash-frozen, Michels me-dium (ammonium sulfate) is the preferred trans-port media for immunofluorescence. Normal saline also performs well.

Figure 1-107 Mib-1 positivity in malignant melanoma. Positive background reactive lymphocytes must be distinguished from Mib-1-positive melanocytes by cytology or double staining technique

Table 1-2 Spindle cell neoplasms

CK Vimentin S100 SMA

Squamous cell carcinoma

+

Atypical fibroxanthoma

+

Malignant melanoma

+ +

Leiomyosarcoma + +

Table 1-3 Small blue cell tumor

S100 Synaptophysin LCA CK

Lymphoma +

Merkel cell carcinoma

+ +

Malignant melanoma

+

Table 1-4 Tumors with intraepidermal buckshot scatter (pagetoid spread)

CK CEA S100 LCA

Pagets disease + +

Bowens disease +

Malignant melanoma +

Mycosis fungoides +

Figure 1-106 CD1a with Langerhans cell histiocytosis