Ch29cP21cTricholemmal
Basosquamous CA

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Fig.P262571

F1Ch29c: The two components of keratinizing squamous epithelium at the top of the field are in continuity with the epidermis. On the left, the squamous cell component shows scattered whorls with small areas of keratinization. The component on the right is characterized by prominent perinuclear vacuoles, a common feature of follicular hamartomas of the butterfly area of the face. The tumor in the deeper portions is composed of basaloid cells; they have scanty, pale cytoplasm, and round or oval, lightly stained nuclei. Focally, basal cells form prominent nuclear palisades. The cells of this component are arranged in a complex pattern of interconnected cords. Focally, the pale, acidophilic stroma is hypocellular, and has a proteinaceous quality. There is some degree of nuclear atypia.

P262trichCAxtr190

F2Ch29c: The tumor cells have a basosquamous quality; hyaline deposits are a prominent feature.

Fig.P262210

F3Ch29c: There is a transition from an epithelial pattern on the right to a myxoid stromal component on the left. Cells forming the cords show degenerative changes with widening of spaces among the tumor cells. The patterns are interpreted as evidence of epithelial cytolysis which, in turn, has provoked reactive fibroplasia with the formation of a delicate myxoid stroma. A microcyst on the right is lined by flattened epithelium. One of the lining cells has a distinct cytoplasmic vesicle; a finding in keeping with sweat duct differentiation. Across the field, to the left, a small epithelial component is acidophilic and multi-microcystic; patterns of this type can be encountered in regenerating sweat ducts.

Fig.P262232

F4Ch29c: Yellow arrows identify sweat duct components within the tumor; some of the epithelial cells of the ductal components have distinct cytoplasmic vesicles of the type commonly seen in neoplastic, or regenerating epithelial cells of sweat ducts. Tumor cells of the nests in the lower portion of the field are fairly well preserved. Near the top of the field, tumor cells show degenerative changes with cytolysis. An area showing loss of the epithelial component and an ingrowth of a myxoid stroma is represented on the right, near the top of the field.

Fig.P262310

F5Ch29c: In this field, the tumor cells have squamoid qualities. There is moderate cytologic atypia. Focally, myxoid stroma is uniformly cellular; it forms an expansile stromal component that compresses the neighboring epithelial component. Near the lower interface with the myxoid stromal component, some of the epithelial cells are spindle shaped and show cytoplasmic acidophilia; they are individually isolated. The patterns suggest spindle cell transformation and an induction of a specialized stroma; a variant of a mixed tumor should be considered in the differential diagnosis. The basic pattern, however, is that of a low-grade, basosquamous carcinoma. Again, the mixed patterns may be evidence of divergent differentiation. Just as mixed tumors of sweat glands may show evidence of hair bulb differentiation, patterns of sweat duct differentiation in a follicular neoplasm should not be a cause for concern.

P262trichCAxtr180

F6Ch29c: The acidophilic portion to the right, at the top of the field, has features of the infundibular portion of a follicle. The bulk of the epithelial component is composed of basaloid cells with pale, or vacuolated cytoplasm; the patterns are of a type commonly seen in follicular hamartomas of the butterfly area of the face. In this field, atypia is mild.

The lesion of chapters 41 & 42 is a pigmented, in-situ process; destructive invasion is not identified on the available sections. There is marked papillomatosis. A neoplastic basal unit is a prominent feature. There are numerous whorls, some of which are keratinizing. The degree of atypia is moderately severe to marked. Papillary carcinoma in situ can be considered as an alternative diagnosis. The histologic features tend to elicit a search for the mental parcel, tricholemmoma, from which a pathologist would pick virtual images to compare with the images of the section.

The lesion of chapter 43 shows features of a catagen-like tricholemmoma; there are a few small areas in which cells of the superficial unit-like component have vacuolated cytoplasm. The cells of the lesion show moderately severe cytologic atypia; cells with superficial unit-like qualities have plump nuclei with marginated chromatin and a prominent nucleolus. Centrally, patterns of sclerosing entrapment are prominent. The lesion has been cut across at the base; an infiltrating carcinoma cannot be ruled out.

In chapter 44, a rather solid, expansile tumor has pushed into the dermis. Stroma is inconspicuous in the nodular component. The epidermis over the lesion is ulcerated. Atypical changes extend in the epidermis away from the nodular component; they involve a neighboring follicle. Although the interface between the nodule and dermis is sharply defined, the lesion has bulk and extends to about the level of the sebaceous glands. Patterns of minimal micro-invasion are apparent in the dermis adjacent to the follicular component.

 

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